Field Exposure Time Research Articles

Study on peculiar carbon pattern formation from polymer blend thin films under electric fields

In this study, we demonstrate the formation of a peculiar carbon pattern from polyacrylonitrile/poly(methyl methacrylate) (PAN/PMMA) blend thin films under external electric fields. When a spin-coated PAN/PMMA blend thin film was exposed to an electric field, the surface of the thin film facing air layer would fluctuate due to the electrohydrodynamic instability phenomenon induced by an electrostatic force. At the same time, the interface between PAN and PMMA would also become unstable because of the difference in the dielectric constants of PAN and PMMA. The microstructure of the PAN/PMMA thin film obtained after field exposure was influenced by the combined effect of the two phenomena. Subsequent controlled thermal treatment produced an unprecedented and peculiar carbon pattern, which remained intact during carbonization. The effect of experimental parameters such as field intensity, exposure time, and film thickness on the microstructure of the polymer precursor and resulting carbon pattern was investigated. This work provides a strategy to obtain carbon structures showing specific surface texture and certain properties that have been inaccessible by any other means.

Performance of a Magnesium-Rich Primer on Pretreated AA2024-T351 in Selected Laboratory and Field Environments: Anodization Pretreatment

The effect of anodization on the corrosion protection of AA2024-T351 by magnesium-rich primer (MgRP) was evaluated in topcoated (TC) and non-TC MgRP systems with and without defects in the form of scribes. Protection of remote scratches and global protection by the coating after exposure in selected laboratory and field environments was investigated. Exposure studies focused on the following pretreatments: anodization without sealing (ANS), anodization with hexavalent chromium sealing (ACS), and anodization with trivalent chromium pretreatment sealing (ATS). Mg pigment depletion rate, global galvanic protection potential of intact coating, and coating barrier properties were investigated. In systems without TC, all chosen environments except for full immersion resulted in complete depletion of Mg pigment resulting from high self-corrosion rates. Polyurethane TC limited the Mg metallic pigment depletion resulting in only partial Mg depletion. In the case of ANS and ATS pretreated AA2024-T351 with MgRP, there was no initial galvanic coupling as inferred by a more positive global galvanic protection potential and predicted by high-pretreatment resistances. Upon prolonged exposure in full immersion, the global galvanic protection potential decreased to more negative potentials with time indicative of gradual galvanic coupling of the AA2024-T351 substrate with the MgRP. This was interpreted as resulting from degradation of the buried anodized layer. In the case of ACS pretreated AA2024-T351 with the MgRP, there was no initial galvanic coupling. After initial lowering of global galvanic protection potential indicating active coupling, there was a shift back to more positive potential. The global galvanic protection potential was heavily mediated by the TC polymer and there was no significant galvanic coupling between AA2024-T351 and Mg in the time frame over which experiments were conducted for TC systems. Mg was preserved and available for any future sacrificial anode-based cathodic protection. The barrier properties of the MgRP pigmented coating also degraded with time at a higher rate in systems in the absence of TC. This was correlated to UV degradation of the pigmented coating resin and could be reduced with the polyurethane TC. Scanning electron microscopy/energy dispersive spectroscopy characterization after different ASTM B117 and field exposure times indicated that the Mg2+ redeposition increased as a function of exposure time in AA2024-T351/ACS/MgRP systems. TC limited the Mg2+ release by mediating both the global galvanic protection potential and Mg self-corrosion. Corrosion volume analysis by optical profilometry indicated that the scribe protection was better for sealed anodization pretreatments compared to the case of anodized without sealing-based systems.

Enhancing filterability of activated sludge from landfill leachate treatment plant by applying electrical field ineffective on bacterial life.

The aim of this study is to investigate filterability enhancement of activated sludge supplied form a full-scale leachate treatment plant by applying DC electric field while keeping the biological operational conditions in desirable range. The activated sludge samples were received from the nitrification tank in the leachate treatment plant of Istanbul's Odayeri Sanitary Landfill Site. Experimental sets were conducted as laboratory-scale batch studies and were duplicated for 1A, 2A, 3A, 4A, and 5A of electrical currents and 2, 5, 10, 15, and 30min of exposure times under continuous aeration. Physicochemical parameters such as temperature, pH, and oxidation reduction potential in the mixture right after each experimental set and biochemical parameters such as chemical oxygen demand, total phosphorus, and ammonia nitrogen in supernatant were analyzed to define the sets that remain in the range of ideal biological operational conditions. Later on, sludge filterability properties such as capillary suction time, specific resistance to filtration, zeta potential, and particle size were measured for remaining harmless sets. Additionally, cost analyses were conducted in respect to energy and electrode consumptions. Application of 2A DC electric field and 15-min exposure time was found to be the most favorable conditions to enhance filterability of the landfill leachate-activated sludge.

Machine Learning for Bioelectromagnetics: Prediction Model using Data of Weak Radiofrequency Radiation Effect on Plants

Plant sensitivity and its bio-effects on non-thermal weak radio-frequency electromagnetic fields (RF-EMF) identifying key parameters that affect plant sensitivity that can change/unchange by using big data analytics and machine learning concepts are quite significant. Despite its benefits, there is no single study that adequately covers machine learning concept in Bioelectromagnetics domain yet. This study aims to demonstrate the usefulness of Machine Learning algorithms for predicting the possible damages of electromagnetic radiations from mobile phones and base station on plants and consequently, develops a prediction model of plant sensitivity to RF-EMF. We used rawdata of plant exposure from our previous review study (extracted data from 45 peer-reviewed scientific publications published between 1996-2016 with 169 experimental case studies carried out in the scientific literature) that predicts the potential effects of RF-EMF on plants. We also used values of six different attributes or parameters for this study: frequency, specific absorption rate (SAR), power flux density, electric field strength, exposure time and plant type (species). The results demonstrated that the adaptation of machine learning algorithms (classification and clustering) to predict 1) what conditions will RF-EMF exposure to a plant of a given species may not produce an effect; 2) what frequency and electric field strength values are safer; and 3) which plant species are affected by RF-EMF. Moreover, this paper also illustrates the development of optimal attribute selection protocol to identify key parameters that are highly significant when designing the in-vitro practical standardized experimental protocols. Our analysis also illustrates that Random Forest classification algorithm outperforms with highest classification accuracy by 95.26% (0.084 error) with only 4% of fluctuation among algorithm measured. The results clearly show that using K-Means clustering algorithm, demonstrated that the Pea, Mungbean and Duckweeds plants are more sensitive to RF-EMF (p <= 0.0001). The sample size of reported 169 experimental case studies, perhaps low significant in a statistical sense, nonetheless, this analysis still provides useful insight of exploiting Machine Learning in Bioelectromagnetics domain. As a direct outcome of this research, more efficient RF-EMF exposure prediction tools can be developed to improve the quality of epidemiological studies and the long-term experiments using whole organisms.

Flow-rate-insensitive deterministic particle sorting using a combination of travelling and standing surface acoustic waves

Manipulation of cells by acoustic forces in a continuous flow offers a means to sort on the basis of physical properties in a contactless, label-free and biocompatible manner. Many acoustic sorting systems rely on either standing waves or travelling waves alone and require specific exposure times to the acoustic field, fine-tuned by manipulating the bulk flow rate. In this work, we demonstrate a flow-rate-insensitive device for continuous particle sorting by employing a pressure field that utilises both travelling and standing acoustic wave components, whose non-uniform spatial distribution arises from the attenuation of a leaky surface acoustic wave. We show that in parts of the pressure field in which the travelling wave component dominates, particles migrate across multiple wavelengths. In doing so, they drift into areas of standing wave dominance, whereby particles are confined within their respective nodal positions. It is demonstrated that this final confinement location is dependent on the particle size and independent of the force field exposure time and thus the flow rate, permitting the continuous separation of 5.1-, 6.1- and 7.0-µm particles. Omitting the need to precisely control the bulk flow rate potentially enables sorting in systems in which flow is not driven by external pumps.

Irreversible electroporation inhibits pro-cancer inflammatory signaling in triple negative breast cancer cells

Low-level electric fields have been demonstrated to induce spatial re-distribution of cell membrane receptors when applied for minutes or hours. However, there is limited literature on the influence on cell signaling with short transient high-amplitude pulses typically used in irreversible electroporation (IRE) for cancer treatment. Moreover, literature on signaling pertaining to immune cell trafficking after IRE is conflicting. We hypothesized that pulse parameters (field strength and exposure time) influence cell signaling and subsequently impact immune-cell trafficking. This hypothesis was tested in-vitro on triple negative breast cancer cells treated with IRE, where the effects of pulse parameters on key cell signaling factors were investigated. Importantly, real time PCR mRNA measurements and ELISA protein analyses revealed that thymic stromal lymphopoietin (TSLP) signaling was down regulated by electric field strengths above a critical threshold, irrespective of exposure times spanning those typically used clinically. Comparison with other treatments (thermal shock, chemical poration, kinase inhibitors) revealed that IRE has a unique effect on TSLP. Because TSLP signaling has been demonstrated to drive pro-cancerous immune cell phenotypes in breast and pancreatic cancers, our finding motivates further investigation into the potential use of IRE for induction of an anti-tumor immune response in vivo.

Magnetic nanoparticle-promoted droplet vaporization for in vivo stimuli-responsive cancer theranostics

The development of efficient strategies for in vivo stimuli-responsive cancer treatment and personalized biomedicine is a great challenge. To overcome the critical issues and limitations of traditional protocols using acoustic droplet vaporization and optical droplet vaporization in stimuli-responsive tumor treatment, we herein report a new strategy, magnetic droplet vaporization (MDV), based on nanobiotechnology, for efficient magnetic field-responsive cancer theranostics. Perfluorohexane (PFH)-encapsulated superparamagnetic hollow iron oxide nanoparticles with a high magnetic-thermal energy transfer capability quickly respond to an external alternating current (a.c.) magnetic field to produce thermal energy and raise the temperature of the surrounding tumor tissue. The encapsulated PFH, with a desirable boiling point of ~56 °C, can be vaporized to enhance the performance of ultrasound imaging of tumors, as systematically demonstrated both in vitro and in vivo. The magnetic–thermal energy transfer further ablated and removed tumors in mice tumor xenograft models. This unique MDV principle with high versatility and performance is expected to broaden the biomedical applications of nanotechnology and promote clinical translations of intelligent diagnostic and therapeutic modalities, especially for battling cancer. Hollow iron nanoparticles can enhance both the imaging and complete removal of tumours in live mice using magnetically simulated heat. Ultrasound molecular imaging is one of the safest ways to track cancerous cell growth, but its success depends on producing gas-filled microbubbles that attach to the targeted tissue. As an alternative to optical or acoustic microbubble generators, Yu Chen from the Shanghai Institute of Ceramics, Yuanyi Zheng from Shanghai Sixth People's Hospital and colleagues have used superparamagnetic iron oxide probes with an encapsulated, low-boiling-point gas inside their nanoshells. After injecting the probes into breast cancer cells, the team applied a non-intrusive alternating-current magnetic field. This stimulus generated thermal energy that raised tissue temperature slightly, releasing numerous microbubbles through vapourization. The ultrasound-guided probes could then heat tumours sufficiently to stop regrowth using longer field exposure times. A novel magnetic droplet vaporization strategy was developed for efficient magnetic field-responsive cancer theranostics. Perfluorohexane (PFH)-encapsulated superparamagnetic hollow iron oxide nanoparticles with high magnetic-thermal energy transfer capability quickly respond to external alternating current (a.c.) magnetic field to produce thermal energy and raise the surrounding temperature of tumor tissue. The encapsulated PFH with desirable boiling point of about 56 °C can be vaporized to enhance the ultrasound imaging performance for responsive imaging. Such a magnetic–thermal energy transfer can further completely ablate and remove the tumor against a mice tumor xenograft model.

Effects of extremely low frequency magnetic field on production of mannatide by α-hemolytic Streptococcus.

The effect of the extremely low frequency magnetic field (ELF-MF) on biomass and mannatide production by α-hemolytic Streptococcus in liquid-state fermentation culture medium was studied during shake flask culture. Magnetic field (MF) inductions, exposure times, and exposure periods varied in a range of 0-1.5 mT, 0-16 h, and six periods of incubation time, respectively. Results showed both biomass and mannatide production increased significantly at MF induction 0.4, 0.6, and 0.9 mT and decreased at both 1.2 and 1.5 mT. Biomass increased by exposure for initial and middle stages of fermentation. Mannatide production increased significantly at 4-8, 8-12, and 17-21 h. Peak yield of biomass and mannatide production increased by 10.7% and 14.0% at 25 and 27 h of incubation at 0.6 mT MF induction and exposure to 8-12 h of incubation time, compared with the control experiment, respectively. ELF-MF could also enhance the growth rate and mannatide production rate of α-hemolytic Streptococcus. However, ELF-MF did not alter α-hemolytic Streptococcus cell growth and mannatide metabolizing regulation or fermentation pattern. Mannatide production was not associated with cellular growth but rather only partially associated. Bioelectromagnetics. 37:331-337, 2016. © 2016 Wiley Periodicals, Inc.

A novel study for determining early life degradation of multi-crystalline-silicon photovoltaic modules observed in western Himalayan Indian climatic conditions

The results of a first time study are reported on the degradation of a roof mounted multi-crystalline-silicon photovoltaic system after 2.5years of outdoor exposure in a western Himalayan location in India. The main objective of the study is to identify frequently occurring defects in modules to study the change in electrical performance parameters and correlate these with identified defects under Indian climatic conditions. A comprehensive test campaign is conducted by visual inspection, thermal imaging and current–voltage characteristic measurements. Early degradation and recently reported defect: snail trails are observed in all modules along with non-uniform single cell browning and junction box failure. Thermal imaging analysis is carried out which shows that three modules developed serious defects like hotspots, disconnected cells and string interconnect ribbons and a significant result that all solar cells located directly on top of junction boxes were 3–8°C hotter than other cells indicating higher thermal degradation rate of these cells than others. Peak power degradation of modules is quantified by measuring performance parameters under standard test conditions as a function of field exposure time, using class-A sun-simulator. Three modules showed 50% degradation while remaining seven modules showed 0.6–2.5% degradation in peak power after 2.5years. PV modules certified as per International Electro-technical Commission (IEC) standards have shown considerable degradation indicating the need to enforce quality control and review qualification standards for Indian climatic conditions if modules have to perform reliably for more than 20years under field conditions. The outcome of the study will be of importance to enhance the knowledge of climate specific field PV degradation mechanism and to provide inputs to Indian/IEC standards, the improvements of which are being considered currently.

Side-effects of electrotrawling: Exploring the safe operating space for Dover sole (Solea solea L.) and Atlantic cod (Gadus morhua L.)

Electrotrawling is currently the most promising alternative for conventional beam trawls targeting sole and shrimp, meeting both the fisherman’s aspirations and the need for more environmentally friendly fishing techniques. Before electrotrawling can be further developed and implemented on a wider scale, more information is needed about the effects of electrical pulses on marine organisms. Adult Dover sole (Solea solea L.) and Atlantic cod (Gadus morhua L.) were used in the present study as model species for flatfish and roundfish, respectively. These animals were exposed to homogeneously distributed electrical fields with varying values of the following parameters: frequency (5–200Hz), electrical field strength (100–200V/m), pulse polarity, pulse shape, pulse duration (0.25–1ms) and exposure time (1–5s). The goal was to determine the range of pulse parameters which can be regarded as safe and thereby also to evaluate the effect of the pulses already being used in commercial electrotrawls. Fish behaviour during and shortly after exposure, 14-days post exposure mortality rates, as well as gross and histological examination were used to evaluate possible effects. During exposure, both species showed an escape response below a frequency of 20Hz and a cramp reaction above 40Hz. These reactions were immediately followed by post-exposure escape behaviour and at high electrical loads cod showed tonic-clonic epileptiform seizures. No mortality was observed and histological examination did not reveal any abnormalities, except for one cod showing a spinal injury. These data reveal the absence of irreversible lesions in sole as a direct consequence of exposure to electric pulses administered in the laboratory, while in cod, more research is needed to assess cod’s vulnerability for spinal injuries when exposed to the cramp pulses.

Determining the safety range of electrical pulses for two benthic invertebrates: brown shrimp (Crangon crangon L.) and ragworm (Alitta virens S.)

Abstract Pulse trawling is currently the most promising alternative for conventional beam trawls targeting sole and shrimp, meeting both the fisher's aspirations and the need for more environmentally friendly fishing techniques. Before electrotrawling can be further developed and implemented on a wider scale, however, more information is needed about the effects of electrical pulses on marine organisms. The organisms used in the present experiments were brown shrimp (Crangon crangon L.) and king ragworm (Alita virens S.) as model species for crustaceans and polychaetes, respectively. These animals were exposed to a homogeneously distributed electrical field with varying values of the following parameters: frequency (5–200 Hz), electrical field strength (150–200 V m−1), pulse polarity, pulse shape, pulse duration (0.25–1 ms), and exposure time (1–5 s). The goal of this study was to determine the range of safe pulses and thereby also to evaluate the effect of the pulses already being used on commercial electrotrawls. Behaviour during and shortly after exposure, 14-d mortality rates, and gross and histological examination were used to evaluate possible effects. The vast majority of shrimp demonstrated a tail flip response when exposed to electric pulses depending on the frequency, whereas ragworm demonstrated a squirming reaction, independent of the frequency. No significant increase in mortality or injuries was encountered for either species within the range of pulse parameters tested. Examination of the hepatopancreas of shrimp exposed to 200 V m−1 revealed a significantly higher severity of an intranuclear baculoform virus infection. These data reveal a lack of irreversible lesions in ragworm and shrimp as a direct consequence of exposure to electric pulses administered in the laboratory. Despite these promising results, other indirect effects cannot be ruled out and further research hence is warranted.

Phenomenological characterization of fabrication of aligned pristine-SWNT and COOH-SWNT nanocomposites via dielectrophoresis under AC electric field

Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques (DEPFT) for obtaining aligned carbon nanotube (CNT)–polymer nanocomposites, and is used here to generate data sets from which DEPFT fabrication models in terms of CNT dispersion and orientation distribution can be developed. While the general understanding of how CNTs form aligned filaments under the influence of dielectrophoretic forces and moments is well established, detailed multi-CNT-filament formation predictions of microstructure evolution from a random dispersion into a more ordered structure remain intractable. As such, effort here is focused towards the development of phenomenological fabrication models for controlling local CNT dispersion and orientation as a function of applied electric field magnitude, frequency, and exposure time. In this study, 0.03 wt% single-wall nanotubes (SWNTs) and acid treated functionalized SWNTs (COOH-SWNTs) were dispersed in a photopolymerizable monomer blend (urethane dimethacrylate (UDMA) and 1,6-hexanediol dimethacrylate (HDDMA)). Ultrasonication techniques were used to obtain the two different acrylate solutions i.e., 0.03% SWNTs/ UDMA/ HDDMA(9/1) solution and a 0.03% COOH-SWNTs/UDMA/HDDMA(9/1) solution, consisting of randomly oriented, well dispersed SWNTs. Pristine SWNTs and acid treated SWNTs solutions were then subjected to controlled AC electric fields in order to explore the formation of aligned SWNT-filaments. To assess key morphological features of the as-produced SWNT-acrylate and SWNT-COOH-acrylate nanocomposite samples, such as SWNT distribution and filament thicknesses, transmission optical microscopy has been used to observe the SWNT alignment and filament formation obtained by digitally mapping individual overlapping images. The acquisition of a large field of view with high magnification allows statistically meaningful distribution functions for morphological features to be constructed. Measurements of the as-produced nanocomposite electrical properties in the SWNT alignment direction and transverse to it were used as a macroscale measure to confirm alignment and contiguity of the SWNT-filament structure, with polarized Raman spectroscopy used to assess the degree of SWNT alignment at the local microscale level. It is observed that a combination of exposure time to AC electric field, and its frequency, is the key driver of filament thickness and spacing and that in general, the COOH-SWNTs align to a greater extent than the pristine SWNTs, though they do not form filaments that are as thick and contiguous for the exposure times studied. POLYM. COMPOS., 36:1266–1279, 2015. © 2014 Society of Plastics Engineers

Coating and interface degradation of coated steel, Part 1: Field exposure

The cathodic delamination (CD) rate of organic coatings on steel can be easily measured with a Scanning Kelvin Probe (SKP). In this paper, the measurement of CD by SKP (CD-SKP) was used for the first time to assess the interface stability after field exposure of polymer-coated steel. The uncoated region used as defect to initiate the CD in the humid SKP chamber was covered during field exposure. The CD rates of the field-exposed samples were compared to unexposed samples to evaluate the interface degradation. The CD-SKP assessment was related to the visual inspection of corrosion products through the transparent coating and electrochemical impedance spectroscopy (EIS) results. The CD rate measured after field exposure corresponded to the site severity that was estimated by the visual inspection. The EIS results were not always reproducible owing to the small exposed area, but overall the coating protection measurements were in accordance with the CD-SKP results. However, CD-SKP was more sensitive and faster than EIS. Furthermore, CD-SKP measurements exhibited clear evidence of improvement of interface stability during the initial stages of field exposure, which was followed by degradation of the interface. The CD-SKP technique can be used in practice to shorten the field exposure time of coated steel and provide early detection of the onset of interface degradation.

Cell behaviors on magnetic electrospun poly-d, l-lactide nanofibers

It is widely accepted that magnetic fields have an influence on cell behaviors, but the effects are still not very clear since the magnetic field's type, intensity and exposure time are different. In this study, a static magnetic field (SMF) in moderate intensity (10mT) was employed to investigate its effect on osteoblast and 3T3 fibroblast cell behaviors cultured respectively with magnetic polymer nanofiber mats. The magnetic mats composed of random oriented or aligned polymer nanofibers were fabricated by electrospinning the mixed solution of poly-d, l-lactide (PLA) and iron oxide nanoparticles. The fiber morphology was characterized by scanning electron microscopy (SEM), the nanoparticle distribution in fiber matrix was measured with transmission electron microscope (TEM). Mechanical properties of nanofiber mats are studied by uniaxial tensile test. The results showed the nanofibers loaded with magnetic nanoparticles displayed excellent magnetic responsibility and biodegradability. In vitro cytotoxicity analysis demonstrated that the osteoblast proliferation of all fiber mats stimulated with or without SMF was increased with the increase of the culturing days. Furthermore, in the horizontal SMFs, cell orientation tended to deviate from nanofiber orientation to field direction while the nanofiber orientation is perpendicular to the field direction, while the horizonal direction of SMFs could also direct the cell growth orientation. The magnetic nanofiber mats provide a potential platform to explore the cell behaviors under the stimulation of external magnetic field.

Seed orientation and magnetic field strength have more influence on tomato seed performance than relative humidity and duration of exposure to non-uniform static magnetic fields

Different factors (e.g., light, humidity, and temperature) including exposure to static magnetic fields (SMFs), referred here as critical factors, can significantly affect horticultural seed performance. However, the link between magnetic field parameters and other interdependent factors affecting seed viability is unclear. The importance of these critical factors affecting tomato (Solanum lycopersicum L.) var. MST/32 seed performance was assessed after performing several treatments based on a L9 (34) (four factors at three levels) orthogonal array (OA) design. The variable factors in the design were magnetic flux density (R1=332.1±37.8mT; R2=108.7±26.9mT; and R3=50.6±10.5mT), exposure time (1, 2, and 24h), seed orientation (North polarity, South polarity, and control – no magnetic field), and relative humidity (RH) (7.0, 25.5, and 75.5%). After seed moisture content stabilisation at the different chosen RH, seeds were exposed in dark under laboratory conditions to several treatments based on the OA design before performance evaluation. Treatments not employing magnetic field exposure were used as controls. Results indicate that electrolyte leakage rate was reduced by a factor of 1.62 times during seed imbibition when non-uniform SMFs were employed. Higher germination (∼11.0%) was observed in magnetically-exposed seeds than in non-exposed ones, although seedlings emerging from SMF treatments did not show a consistent increase in biomass accumulation. The respective influence of the four critical factors tested on seed performance was ranked (in decreasing order) as seed orientation to external magnetic fields, magnetic field strength, RH, and exposure time. This study suggests a significant effect of non-uniform SMFs on seed performance with respect to RH, and more pronounced effects are observed during seed imbibition rather than during later developmental stages.

Investigation on the effect of static magnetic field up to 15 mT on the viability and proliferation rate of rat bone marrow stem cells

This investigation was performed to evaluate the influence of the static magnetic field up to 15mT on the viability and proliferation rate of rat bone marrow stem cells. Cells from passage 5 were trypsinized, and a cell suspension was prepared. The cells were counted and cultured in 25-cm(2) flasks. They were incubated for 1d, washed with phosphate-buffered saline, and then exposed with different intensities of static magnetic field (4, 7, and 15mT) at different exposure times (24, 48, 72, and 96h). Cells were then washed with phosphate-buffered saline, trypsinized, and a cell suspension was prepared separately from each flask. To investigate the viability and proliferation rates of treated cells, staining with Trypan blue and counting were performed with an optical microscope. The mean number of whole cells and living cells was considered as proliferation and survival rates, respectively. Increasing of intensity and time of static magnetic field exposure decreased the viability percent and proliferation rate in treated groups compared with corresponded control. However, reduced cell viability, where this occurred, is exclusively due to apoptosis since necrosis is never observed by others.

Effect of reproductive status, magnetic field exposure and photoperiod on temporal organization in air-gulping activity in Clarias batrachus

The present study examined effects of pulsed magnetic field exposure (daily one hour magnetic field exposure at two times, 08:00–09:00 h and 16:00–17:00 h, 4000 Gauss) and continuous magnetic field exposure (4000 Gauss) for 30 days under LD (12:12), LL, and DD on temporal organization in air gulping activity in Indian freshwater catfish, Clarias batrachus, during different phases of its annual reproductive cycle. The air-gulping activity was monitored manually for about 15 minutes at four time-points (08:00 h, 12:00 h, 14:00 h, and 16:00 h) in each group. Time of day, photoperiod and magnetic field exposure all produced statistically significant effects on air-gulping activity during different phases of the annual reproductive cycle, excluding the spawning phase. The changes due to magnetic field exposure did not depend upon photoperiod. During most of the phases of the reproductive cycle, an increase or decrease in air-gulping activity was observed under DD and LL, respectively. It is concluded that air-gulping activity in C. batrachus exhibits daily variation, and that magnetic field exposure and photoperiod both produce modulatory effects on such activity.

ENHANCEMENT OF INVERTASE PRODUCTION BY Aspergillus niger OZ-3 USING LOW-INTENSITY STATIC MAGNETIC FIELDS

The aim of this study is to investigate the effect of low-intensity static magnetic fields (SMFs) on invertase activity and growth on different newly identified molds. The most positive effect of SMFs on invertase activity and growth was observed for Aspergillus niger OZ-3. The submerged production of invertase was performed with the spores obtained at the different exposure times (120, 144, 168, and 196 hr) and magnetic field intensities (0.45, 3, 5, 7, and 9 mT). The normal magnetic field of the laboratory was assayed as 0.45 mT (control). Optimization of magnetic field intensity and exposure time significantly increased biomass production and invertase activity compared to 0.45 mT. The maximum invertase activity (51.14 U/mL) and biomass concentration (4.36 g/L) were achieved with the spores obtained at the 144 hr exposure time and 5 mT magnetic field intensity. The effect of low-intensity static magnetic fields (SMFs) on invertase activities of molds was investigated for the first time in the present study. As an additional contribution, a new hyper-invertase-producing mold strain was isolated. Supplemental materials are available for this article. Go to the publisher's online edition of Preparative Biochemistry and Biotechnology to view the supplemental file.

Faecal spectroscopy: a practical tool to assess diet quality in an opportunistic omnivore

Faecal indices of dietary quality can provide useful knowledge about the general ecology of a species, but only if the measurements are accurate and the results are interpreted with caution. In this article, we evaluated the potential of near‐infrared spectroscopy (NIRS) as an analytic tool to derive faecal indices of dietary quality in an omnivorous monogastric species with a wide dietary range, i.e. the brown bear Ursus arctos. We also tested the effects of field exposure on faecal constituents (i.e. nitrogen, lignin, crude fiber (CF), ether extracts (EE), acid detergent fiber (ADF), neutral detergent fiber (NDF), ash and dry matter (DM)), which are commonly used as faecal indices of dietary quality. We collected 172 faecal samples from 45 GPS‐marked brown bears in south‐central Sweden between May and October 2010. For each sample, we recorded maximum field exposure time (in hours) and canopy cover (in %). We used multivariate partial least‐squares regression with a segmented cross validation procedure to calibrate the NIRS method. We obtained very good (r2 ≥ 0.9) NIRS validation results for faecal nitrogen content and NDF, and good (0.7 ≤ r2 &lt; 0.9) results for lignin, CF, EE, ADF and ash. Validation results for DM were poor (r2 = 0.29). We found that field exposure time negatively affected faecal nitrogen content, especially during the first 40 hours of exposure. Because CF and NDF are strongly negatively correlated with faecal nitrogen content, concentrations of these two components increase as a consequence of field exposure. Faecal EE content appeared to be stable under field conditions. Our conclusions are twofold. First, NIRS can be an accurate, fast and inexpensive analytical tool to evaluate certain faecal indices of dietary quality, including for omnivorous species. Second, faecal indices of dietary quality can be affected by field exposure and can vary among individual animals. Ignoring individual variance and the effects of field exposure on faecal indices of dietary quality may cause bias in research findings.

Performance analysis of field exposed single crystalline silicon modules

This paper presents results on the field performance degradation of mono-crystalline silicon PV modules from 11 PV module manufacturers under identical field conditions. The modules were installed in both fixed tilt and manual tracking modes. The data were monitored using a CR23X Data logger and I– V curves were taken using SPI 240A Sun simulator. The performance parameters analyzed are V oc, I sc, P max, I mp, V mp and the fill factor, as a function of time of field exposure. Qualitative studies are made on physically visible defects such as EVA coloration, cell de-laminations, corrosion of solar cell grid, corrosion of end strip connected in the terminal box, failure of by-pass diode, detachment of the terminal box, tearing of tedlar sheet, etc. The effect of field exposure on the performance parameters indicates that the qualification standard (s) needs to be reviewed and revised if the modules are to perform for ∼20 years under actual field conditions in India.