Longer Exposure Times Research Articles

Effect of temperature and aging duration on ethylene propylene diene monomer (EPDM) nonmetallic components used in caustic liquid waste transfer lines

Nonmetallic materials are used in waste transfer lines at the United States Department of Energy’s Hanford Site Tank Farm in Benton County, Washington, USA. During use, the ethylene propylene diene monomer (EPDM) inner hose of the hose-in-hose transfer lines (HIHTLs) are exposed to β and γ radiation, caustic solutions as well as high temperatures and high pressures. Aging behavior of specimens of EPDM HIHTLs and dog-bone shaped specimens were evaluated by exposing to a solution of 25% sodium hydroxide (NaOH) at 38 °C, 54 °C and 77 °C for 6 and 12-months as well as water only at 77 °C for 12-months. Tensile strength and burst pressure of the specimens were characterized and compared with the unexposed (baseline) specimens. Both the tensile strength of the EPDM material and the burst pressure of the HIHTLs significantly decreased with the higher temperatures and longer exposure times. Analyses using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) of the HIHTLs and the dog-bone specimens were conducted. Results show that the surface degradation increased with increasing exposure temperature. Penetration of NaOH into the EPDM material also increased with increasing temperature and exposure duration.

Structural, morphological, optical and photoelectrochemical properties of ZnFe2O4 thin films grown via an electrodeposition method

Various zinc ferrite (ZnFe2O4) nanostructures were successfully synthesized by an environmentally-friendly, facile, cost-effective and simple one-step electrodeposition method. ZnFe2O4 film on fluorine-doped tin oxide glass (FTO) were prepared at different times (10 s, 40 s, 60 s, 120 s, 180 s) by electrodeposition method. The phase structural, morphological and the photoelectrochemical (PEC) properties are studied by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), linear sweep voltammetry (LSV), chronoamperometry (CA) and open circuit potential (OCP). Ultraviolet–visible (UV–Vis) diffuse reflection spectroscopy was performed to study band gap and optical absorption properties. Based on the experimental results, the maximum amount of photocurrent was taken from the sample with an electrodeposition time of 60 s. The precipitate was removed from the FTO surface as longer exposure time was applied. Electrodeposition time changes the morphological properties of the surface as a result increasing the deposition time, the sheet-like nanostructures were formed.

Two class II CPD photolyases, PiPhr1 and PiPhr2, with CPD repair activity from the Antarctic diatom Phaeodactylum tricornutum ICE-H.

The online version contains supplementary material available at 10.1007/s13205-021-02927-0.

Focus on lasers, imaging, microscopy, and nanoscience

Focus on lasers, imaging, microscopy, and nanoscience

Investigation of crevice corrosion of metallic fastened joints in carbon fiber reinforced polymer (CFRP) exposed to coastal seawater

Purpose The purpose of this paper is to study the susceptibility of these three commonly used corrosion resistance fasteners in seawater. For a more practical scenario, a local Atlantic coastal seawater as received was used. Design/methodology/approach Carbon fiber reinforced polymer (CFRP) was fabricated with T700 carbon fiber (Toray Inc.) and VE8084 vinyl ester resin (Ashland) to make a unidirectional composite panel of thickness 1.8 mm. A conductive paint was applied to one of the sample edges that was perpendicular to the fiber direction, providing an electrical contact with carbon fibers to connect a copper wire. This external electric connection was used for potential measurements of both the open circuit potential (OCP) of the CFRP sample, and the mixed potential of the fastened set: consisting of the CFRP and the metallic fastener fastened to it. Three common fastener alloys were selected: 316SS, Monel and Titanium. For this purpose, a high impedance voltmeter was used in conjunction with a saturated calomel reference electrode. Measurements were taken daily. For longer time measurements, a four-channel high impedance analog data logger was used with 30 min sampling rate. Findings For both 316SS and Monel fastened sets, crevice corrosion occurred inside the occluded regions of the set, when immersed in coastal seawater. The attack was more severe for 316 stainless steel set. An isolated island attack of faceted surfaces morphology was seen for 316SS set. While, a circular ring of preferential grain boundary attack appeared for Monel set, indicating an IR (voltage) drop mechanism is more likely operating. Titanium-fastened sets showed high resistance to crevice corrosion when simmered in seawater. However, for long-time exposure, the sets became more susceptible to crevice corrosion attack supported by CFRP attachment (oxygen reduction reaction taking place at the carbon fibers). Originality/value Evidently, titanium, stainless steels and Monel are good candidates for galvanic corrosion resistance. However, their susceptibility to crevice corrosion when coupled with CFRP is a new challenging topic that needs further investigation. This is very important today because the vast application witnessed for CFRP material. This work involves developing an original methodology for this kind of investigation and was done at advanced laboratories of SeaTech at Florida Atlantic University by the Atlantic coastline.

Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles.

Gold nanoparticles (~10 nm) were deposited on titanium dioxide nanoparticles (~21 nm) and the material obtained was characterized using IR, UV-Vis, N2 adsorption–desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded in the presence of this material when using hydrogen peroxide as the oxidant. Tests were performed at 2, 4, 6, and 24 h, with hydrogen peroxide contents varying from 1 to 5 mg/mL. Longer exposure time and a higher content of oxidant led to the degradation of methylene blue dye at up to 90%. The material can be reused several times with no loss of activity.

Electromagnetism as an Inductor of Biomass Synthesis in Brassica Napus L. Plants

In recent times, the use of magnetic fields has been used to stimulate germination processes in vegetables seeds, without deepening in their interaction with the variables of growth, development and productivity of these. In this regard, this research characterized the effect of induced electromagnetic fields on the production and composition of the biomass of plants of Brassica napus L.; It is noteworthy that electromagnetic fields are generated from moving electrical charges, and the Tesla is the magnetic induction unit (or magnetic flux density) defined by the International System of Units (SI). Likewise, for the induction process of electromagnetic fields, coils were used, which with the help of a power source kept the variables of volts (V) and amps (A) fixed in time, thus guaranteeing the constant intensity of the field generated. A 3 x 4 bifactorial experimental design was used, where 3 are the field intensities and 4 the exposure times to be evaluated. In this context, biomass yield, growth and development characteristics, as well as bromatological characteristics of biomass were determined. For the study of these effects, a statistical analysis was performed using the Statgraphics 5.1 PLUS software, performing an analysis of ANOVA with 95% confidence to establish if there are significant differences between the treatments, as well as a multiple range test. In consequence of the experimental process, the results show a significant increase in the variables studied, mainly in biomass and synthesis of photosynthetic pigments at longer exposure times and lower intensities. Further, the variables studied for the growth and development of the plants of B. napus L.; confirming this way, a direct stimulation of these processes.Keywords: electromagnetic fields, germination processes, biomass, Grown and develo

Evaluation of the influence of B and Nb microalloying on the microstructure and strength of 18% Ni maraging steels (C350) using hardness, spherical indentation and tensile tests

Microalloyed steels with very small amounts of B and/or Nb are expected to enhance their mechanical properties. In the present work, we have designed and conducted experimental assays for evaluating the merits of microalloying 18% Ni maraging steels with small amounts of B and Nb. The experiments included the synthesis of small volumes of material with the desired compositions (labeled base alloy, alloy I, and alloy II), aging heat treatments, and mechanical property evaluation using a combination of Vickers hardness, spherical indentation stress-strain protocols, and standardized tensile tests. The microstructures of the alloys were studied using SEM/EDS, EBSD, and X-ray diffraction (XRD). The results of this study have demonstrated that the microalloyed steels with B and Nb delayed the coarsening of precipitates and retained their peak aged strength over longer exposure times in the aging process. Furthermore, comparing the estimates from hardness and the spherical indentation stress-strain protocols with the standardized tensile tests indicated that the spherical indentation protocols provided highly reliable estimates of the tensile yield strengths at significantly lower cost and effort. This study has confirmed the viability of utilizing the spherical indentation stress-strain protocols for the rapid exploration of materials composition and process spaces.

Holographic Grating Enhancement of TI/PMMA Polymers in the Dark Diffusion Process.

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect.

Toxic effects of norfloxacin in soil on fed and unfed Folsomia candida (Isotomidae: Collembola) and on gut and soil microbiota

Soils contaminated with antibiotics may exert effects on soil-dwelling animals. A systematic ecological toxicity assessment of norfloxacin on the soil collembolan Folsomia candida (F. candida) was therefore conducted in soil and Petri dish systems with and without feeding at the population, individual and cellular levels. The indicators survival, reproduction, antioxidant enzyme activities peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD), malondialdehyde (MDA) contents and gut microbiota were studied. The surrounding soil microbiota were also investigated because F. candida can ingest soil microbiota that may have effects on the gut microbiota. In general, the toxicity of norfloxacin to F. candida in contaminated soil without food addition was higher than in contaminated soil with food addition. Norfloxacin had little effect at population and individual levels but antioxidant enzyme activities changed significantly in treatments with longer exposure times or higher norfloxacin concentrations. CAT was more sensitive than SOD or POD. The diversity indices and composition at phylum level of the gut microbiota showed little change. However, the operational taxonomic units in the gut decreased in the presence of norfloxacin. The relative abundance of Wolbachia, the predominant bacterial genus in the gut, decreased significantly with increasing soil norfloxacin concentration. Wolbachia may therefore be a promising bioindicator in the assessment of norfloxacin pollution of soils at environmental concentrations.

Effects of tungsten addition on the microstructural stability and properties of Ti-6.5Al-2Sn-4Hf-2Nb-based high temperature titanium alloys

The microstructural evolution, oxidation resistance and mechanical properties of Ti-6.5Al-2Sn-4Hf-2Nb-based alloys with different contents of tungsten (W) additions ranging from 0 to 4.0 wt.% have been investigated in this study. The addition of W changed the microstructure from Widmanstätten colony of the W-free alloy to basketweave microstructure. After thermal exposure at 650 °C for 1000 h, the retained β phase became less continuous, and secondary β nano-particles with high W concentration were precipitated from α lamellas. Within α lamellas, the W was found to mainly partitioned into the secondary β phase and refined the ordered α2-Ti3Al precipitates due to increased solubility of Nb in α2 phase. High W addition increased activation energy for oxidation, promoting the formation of more uniform and compact compound oxides, therefore substantially enhanced the oxidation resistance of the alloy. Besides, the W addition also improved the room and high-temperature yield strength without obviously losing plasticity after long-time thermal exposure. The improved mechanical performance was mainly attributed to the introduction of more α/β interfaces, the precipitation of secondary β phase and the refined α2 phase with Nb segregation.

One-pot scalable in situ growth of highly corrosion-resistant MgAl-LDH/MBT composite coating on magnesium alloy under mild conditions

Current corrosion-resistant layered double hydroxide (LDH) coating on Mg alloy is usually in situ grown in autoclave by hydrothermal methods under high temperature and high-pressure conditions, which is unfavorable for industrial application. We report that an inhibitor (2-mercaptobenzothiazole, MBT) incorporated composite (MgAl-LDH/MBT) coating can be in situ deposited on bare AZ31 Mg alloy surface with the assistance of a chelating agent (ethylenediaminetetraacetic acid) under a relatively low temperature (95 °C) and ambient pressure by a one-pot method. The successful formation of LDH/MBT composite coating is confirmed by a series of characterizations, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). The corrosion resistance of the composite coating is evaluated by means of hydrogen evolution measurement, electrochemical impedance spectroscopy (EIS), Tafel polarization curves, and neutral salt spray test. The tests show that the LDH/MBT composite coating has a very low corrosion current density (1.73 10−8 A cm−2), an extremely high charge transfer resistance (2.336 MΩ cm2), and does not show any corrosion pits even after 15 d of exposure to a NaCl solution or 7 d of exposure to salt fog environment, manifesting the good and robust corrosion protection. Lastly, the deposition and corrosion protection mechanisms of the MgAl-LDH/MBT composite coating are also discussed and proposed based on the EDS characterization of the coating after long-time exposure.

Inactivation of Listeria monocytogenes and Salmonella on Stainless Steel by a Piezoelectric Cold Atmospheric Plasma Generator

Cold atmospheric pressure plasma (CAP) is a novel non-thermal technology that is gaining increasing importance as a decontamination method. Stainless steel is a widespread food contact surface used in food-processing environments. In this study, for the first time, a low-voltage piezoelectric CAP device that uses ambient air was assessed for its antimicrobial efficiency against Salmonella and Listeria monocytogenes. These inoculated on stainless steel at different exposure times (0–300 s), two different distances (10 and 20 mm), and two different cleanliness levels (clean and protein-soiled). Two inactivation models were compared to study the inactivation kinetics of the pathogens. The results showed that CAP treatment effectively reduced L. monocytogenes and Salmonella levels. The Weibull + tail model showed better goodness of fit than the Weibull model. Protein-soiled coupons showed a protective effect to cold plasma inactivation achieving lower reductions compared to clean stainless-steel coupons for both L. monocytogenes and Salmonella. Longer distances from the plasma source decreased the decontamination efficiency of CAP; however, the difference in pathogen reduction was less pronounced at longer exposure times. This study demonstrates the capacity of a low-voltage piezoelectric CAP device to effectively reduce the levels of both foodborne pathogens on stainless-steel surfaces and the potential to adopt this technology by the food industry as a disinfection process of surfaces to reduce cross-contamination and thus increase safety.

Tuning the Photoelectrochemical Properties of Narrow Band Gap Nanoporous Anodic SnOx Films by Simple Soaking in Water.

Nanoporous tin oxide layers obtained via anodic oxidation of metallic tin at the potential of 4 V in the alkaline electrolyte (1 M NaOH) were soaked in distilled water for various durations (from 2 h to 120 h) to verify the influence of water-enabled crystallization on the morphology, composition, and related optical and photoelectrochemical properties of such kind of anodic SnOx. Although water soaking generally contributes to more stoichiometric and crystalline tin oxide, it was confirmed that at the initial stages of the water-induced dissolution–redeposition process, material exhibits enhanced photoelectrochemical performance under simulated sunlight irradiation. However, long-time exposure to water results in a gradual widening of the material’s band gap, shifting of the photoelectrochemical spectra towards higher energies, and almost complete deterioration of the photoelectrochemical activity under sunlight irradiation.

Cytotoxic effect of sodium hypochlorite (Lavanox 0.08%) and chlorhexidine gluconate (Irrisept 0.05%) on human osteoblasts

PurposeSoft tissue, bone and joint infections are severe complications in orthopedic and traumatological surgery. Lavanox (0.08% NaOCl) and Irrisept (0.05% chlorhexidine gluconate, CHG) are industrially produced antiseptic solutions commonly used in infection treatment. Regarding this clinical indication, the microbicidal effect is often investigated, but toxicity to osteoblasts has rarely been examined. This is important to decide whether these solutions should be used in septic situations in which bone healing must take place. The hypothesis of the present study is that NaOCl and CHG are cytotoxic to osteoblasts even after a short exposure time.MethodsHuman osteoblasts were isolated from donors with osteoarthritis during total knee and hip arthroplasty. Cells were cultivated and treated with both antiseptic solutions for 2, 5 and 10 min in different dilutions. Toxicity was quantified by counting cells, lactate dehydrogenase (LDH) expression, spectrophotometric quantification via XTT assay and FDA/PI fluorescence microscopy.ResultsAnalyzing viable cells after treatment with both antiseptics showed a significant decrease in viable cells through LDH expression test, XTT assay, fluorescence microscopy and light microscopy, depending on concentration. The time dependence showed a trend to more cell death at longer exposure times, without significance.ConclusionToxic effects on osteoblasts were shown after treatment with 0.08% NaOCl and 0.05% CHG after an exposure time of 2 min which also was concentration dependent. There was no difference in cytotoxicity between both antiseptics. In conclusion, these antiseptic solutions may be used with caution in situations requiring bone healing.Trial registration numberLocal ethics committee registration number: 5176–07/16

Acute toxicity and biomarker responses in Gammarus locusta amphipods exposed to copper, cadmium, and the organochlorine insecticide dieldrin.

The toxicity of copper, cadmium, and dieldrin in adult Gammarus locusta (a marine amphipod) is currently unclear. Thus, G. locusta from the North Lake of Tunis were subjected to acute toxicity tests to assess LC50s at 48-96 h and to biomarker response tests through the assessment of catalase and acetylcholinesterase activities and malondialdehyde levels. The present study demonstrated the abilities of a chlorinated hydrocarbon pesticide (dieldrin) induce to oxidative stress and neurotoxicity. The comparison of metal toxicity showed that G. locusta was more sensitive to cadmium than copper. The three stressors caused significant inductions of all three biomarkers in a concentration-dependent manner. Catalase induction was dependent on exposure duration for all pollutants, while only copper led to increased malondialdehyde with longer exposure times. Catalase induction and malondialdehyde increase appeared to be sex dependent for all three pollutants. The neurotoxic effects of the pollutants were concentration dependent according to inhibition of acetylcholinesterase activity. In conclusion, catalase, malondialdehyde, and acetylcholinesterase are efficient biomarkers of copper, cadmium, and dieldrin in G. locusta.

Investigating the cause of hemolysis in patients supported by a pulsatile ventricular assist device.

A survey conducted by Abiomed, Inc. revealed that 10 of 60 patients who received ventricular assistance via the AB5000 ventricular assist device (VAD) experienced hemolysis. The present study was conducted to investigate which factors influence hemolysis under pulsatile-flow VADs such as the AB5000. We compared the specificity of the AB5000 and its driving console with those of the NIPRO-VAD and VCT50χ under severe heart failure conditions using a mock circulatory system with a glycerol water solution. We used the mock circuit with bovine blood to confirm which pump conditions were most likely to cause hemolysis. In addition, we measured the shear velocity using particle image velocimetry by analyzing the seeding particle motion for both the AB5000 and NIPRO-VAD under the same conditions as those indicated in the initial experiment. Finally, we analyzed the correlation between negative pressure, exposure time, and hemolysis by continuously exposing fixed vacuum pressures for fixed times in a sealed device injected with bovine blood. Applying higher vacuum pressure to the AB5000 pump yielded a larger minimum inlet pressure and a longer exposure time when the negative pressure was under - 10mmHg. The plasma-free hemoglobin increased as more negative pressure was driven into the AB5000 pump. Moreover, the negative pressure interacted with the exposure time, inducing hemolysis. This study revealed that negative pressure and exposure time were both associated with hemolysis.

Dose-independent threshold illumination for non-invasive time-lapse fluorescence imaging of live cells

Fluorescent microscopy employs monochromatic light for excitation, which can adversely affect the cells being observed. We reported earlier that fibroblasts relax their contractile force in response to green light of typical intensity. Here we show that such effects are independent of extracellular matrix and cell lines. In addition, we establish a threshold intensity that elicits minimal or no adverse effect on cell contractility even for long-time exposure. This threshold intensity is wavelength dependent. We cultured fibroblasts on soft 2D elastic hydrogels embedded with fluorescent beads to trace substrate deformation and cell forces. The beads move toward cell center when cells contract, but they move away when cells relax. We use relaxation/contraction ratio (λr), in addition to traction force, as measures of cell response to red (wavelength, λ=635-650 nm), green (λ=545-580 nm) and blue (λ=455-490 nm) lights with varying intensities. Our results suggest that intensities below 57, 31 and 3.5 W/m2 for red, green and blue lights, respectively, do not perturb force homeostasis. To our knowledge, these intensities are the lowest reported safe thresholds, implying that cell traction is a highly sensitive readout of the effect of light on cells. Most importantly, we find these threshold intensities to be dose-independent; i.e., safe regardless of the energy dosage or time of exposure. Conversely, higher intensities result in widespread force-relaxation in cells with λr > 1. Furthermore, we present a photo-reaction based model that simulates photo-toxicity and predicts threshold intensity for different wavelengths within the visible spectra. In conclusion, we recommend employing illumination intensities below aforementioned wavelength-specific thresholds for time-lapse imaging of cells and tissues in order to avoid light-induced artifacts in experimental observations.

Toxicity of the recombinant human hyaluronidase ALT-BC4 on embryonic development.

Cumulus-oocyte complexes (COCs), which contain immature oocytes, are matured in vitro for in vitro embryo production. Oocyte and cumulus cells are then separated using hyaluronidase. To date, there have only been a few reported cases of the toxic effects of hyaluronidase on porcine oocytes. The aim of this study was to compare the effects of bovine testis-derived hyaluronidase and recombinant human hyaluronidase on oocyte denudation and quality. Porcine COCs were matured for 44 h and denuded using different hyaluronidase concentrations and exposure times. Then, oocytes were activated by electrical parthenogenesis. In experiment 1, COCs were denuded using bovine-derived, ovine-derived (Hirax), and human recombinant (ALT-BC4) hyaluronidases for 10 and 20 min. In experiment 2, bovine-derived and human recombinant (ALT-BC4 and ICSI Cumulase®) hyaluronidases were used to denude the COCs for 2 and 20 min. In both experiments the oocytes were all completely denuded, and there was no degeneration. Rate of embryo development was significantly increased in group treated ALT-BC4 for 2 min and not significantly different in other treatment groups. In general it slightly decreased with longer exposure times. These results have confirmed that different sources of hyaluronidase do not have detrimental effects on the quality of porcine oocytes and suggest that the human recombinant hyaluronidase ALT-BC4 is suitable for oocyte denudation with an increased blastocyst rate.

Effect of Long-time Postnatal Exposure to Sevoflurane on Causing Attention-deficit/Hyperactivity Disorder in Rats

To investigate whether long-term exposure to inhaled sevoflurane, a volatile anesthetic, causes abnormal activities and memory impairment related to attention-deficit/hyperactivity disorder (ADHD) in neonatal rats. On postnatal day 5 (P5), Sprague-Dawley rats were randomly assigned to two sevoflurane subgroups and two control subgroups and underwent experimental intervention. The two sevoflurane (SEVO) subgroups were exposed to 3% sevoflurane for 2 h and 4 h respectively, while the two control subgroups were given pure oxygen for the same amount and duration. Behavioral tests, including open-field test (OFT), five-choice serial reaction time task (5-CSRTT), fear-conditioning (FC) and Morris water maze (MWM), were applied to evaluate changes in cognition, memory, anxiety and ADHD-related behavioral changes in the rats in adolescence (-P25) and in adulthood (-P65). In OFT, the SEVO 2 h and SEVO 4 h subgroups displayed activity level and exploratory behaviors similar to those of the control subgroups on P21 and P61, with no statistically significant difference identified in the data. 5-CSRTT results on P25 and P65 indicated no statistically significant difference between the SEVO subgroups and the control subgroups in regard to ADHD-related abnormal behaviors, including number of immature reaction, rate of correct response and omission rate. In the FC experiment, SEVO 4 h group had a shorter freezing period and longer period of freezing latency ( P=0.029) in comparison to the control groups. The results of the MWM test showed that the escape latency period of rats in the SEVO 4 h group was significantly prolonged on the second day and the third day, compared to the control groups ( P<0.05). The average swimming speed of SEVO groups did no exhibit any statistically significant difference on P69 or P76. The time the SEVO 4 h group spent in the target quadrant was significantly shorter than that of the control group ( P=0.039) and percentage of distance traveled in the target quadrant was significantly reduced compared to that the control group ( P=0.048). The findings suggest that four hours of inhaled sevoflurane exposure in neonate rats may cause memory impairment, but does no increase risks for ADHD-related abnormal activities.