Μm Min Research Articles

Physical processing or supplementation of feeds with phytogenic compounds, alginate oligosaccharide or nucleotides as methods to improve the utilization of Gracilaria gracilis by juvenile European seabass (Dicentrarchus labrax)

This study assessed both the effectiveness of a physical-mechanical rupture method and the ability of feed additives (phytogenic compounds, alginate oligosaccharide and nucleotides) to enhance the utilization of G. gracilis by European seabass. A commercial-based diet was used as control diet (CTRL) and compared with five isoproteic (53.5% Dry matter, DM) and isolipidic (14.9% DM) diets containing 8% of G. gracilis. This seaweed was either unprocessed (diet GRA) or subjected to physical processing (diet GRAP). The three additive-containing diets were formulated by supplementing the GRA diet with either 0.02% phytogenic compounds (PHY), 2.5% oligo-alginate (OAS) or 0.08% free nucleotides (NUC). Triplicate groups of nineteen fish (29.7 ± 0.02 g) were distributed by 50 L tanks (11.3 kg m−3) and fed the experimental diets to satiety during 106 days. By the end of the trial, growth performance and nutrient utilization (specific growth ratio, feed conversion ratio, apparent digestibility coefficients, nutrient balance, intestinal brush border membrane enzyme activities and plasma metabolic parameters), gut histomorphology, antioxidant and immunological status of fish were evaluated. The ability of fish to digest seaweed-rich diets was largely improved by the technological processing of G. gracilis, albeit nil effect on fish specific growth rate (1.0 in all groups). This major achievement was associated with increased ability of GRAP to digest protein (84 vs 68% in GRA) and energy (64 vs 38% in GRA). The use of feed additives in Gracilaria-rich diets was less efficacious in improving European sea bass nutrient and energy ADCs, but have still improved the overall digestibility of those diets. Fish fed alginate oligosaccharide was mainly associated with increased activity of anterior intestine enzymes, particularly intestinal alkaline phosphatase (IAP; 174.4 vs 104.7–120.6 μm min−1 g−1 in Gracilaria-rich diets). Moreover, the algae technological processing and both the nucleotides and the alginate oligosaccharide seem to have positively affected the intestinal villus width compared to the negative impact seen in fish fed GRA. The tested additives had limited impact on oxidative stress, although glutathione peroxidase (GPx; 2.1 μmol min−1 mg protein−1) and catalase (CAT; 35 μmol min−1 mg protein−1) activities were lowest in fish fed NUC and PHY, respectively. It can be concluded that the physical processing of Gracilaria sp. or the addition of either oligo-alginate or nucleotides can effectively increase the nutritional value of this seaweed for European seabass diets.

A novel Pb/PbO2 electrodes prepared by the method of thermal oxidation-electrochemical oxidation: Characteristic and electrocatalytic oxidation performance

The PbO2 electrodes were preservative and chemically stable but had the problem of the poor electrocatalytic oxidation activity and instability. In this research, Pb/PbO2 electrodes with good electrocatalytic oxidation activity and stability were prepared via a novel combined method of thermal oxidation and electrochemical oxidation, which was different form electrodeposition and coating method. Combined with the results analyzed by SEM, metallographic microscope, XRD, steady-state polarization and CV tests, the electrocatalytic oxidation performance was evaluated by the generation capacity of ·OH and the removal efficiency of Congo red (CR). The experimental results put in evidence that the electrochemical oxidation time affected the electrochemical oxidation performance of Pb/PbO2 electrode by refinement of crystal sizes and strengthening of crystallinity which promoted oxygen evolution potential and ·OH generation ability. The better ·OH generation ability of 6-PbO2 encouraged the removal of CR (68.62%, 0.177 min−1) whose chromophore and ring structure of aromatic hydrocarbons was destroyed by ·OH (7.82 × 10−4 μM min−1) with initial concentration of 20 mg·L-1 at 8 mA·cm-2 for 20 min. Moreover, 6-PbO2 owned stability for its compact surface. It showed that the stable 6-PbO2 electrode prepared by the thermal oxidation-electrochemical oxidation method had good electrocatalytic oxidation activity and excellent application potential, which were worthy of further research.

Fast growth of highly ordered porous alumina films based on closed bipolar electrochemistry

Highly ordered porous anodic alumina (PAA) is widely used as a template for preparing one-dimensional nanostructured materials. At present, research efforts to prepare PAA templates with straight channels mainly focus on improving their regularity or increasing the efficiency of the preparation methods. Herein, we introduce a novel anodization method to fabricate highly ordered PAA films based on closed bipolar electrochemistry. To the best of our knowledge, there have been no reports of the use of closed bipolar electrochemistry in PAA film fabrication. Compared to traditional anodization, a faster PAA film growth rate of 1.67 μm min−1 was obtained in 0.75 M oxalic acid when a voltage of 62 V was applied to the driving electrodes. Furthermore, different electrolyte solutions can be employed in the anodic and cathodic cells in the closed bipolar electrochemical system. In addition, no direct electrical connection to the aluminum sheets is required in this approach.

Inflammatory biomarker detection in milk using label-free porous SiO2 interferometer

N-acetyl-β-d-glucosaminidase (NAGase) is an established indicative biomarker released upon damage or necrosis of tubular epithelial cells in both humans and animals, indicating severe nephrological disorders and bovine mastitis (BM), respectively. The latter is the most common and costly disease in dairy cattle associated with production losses, elevated somatic cell counts and deteriorated health status. Herein, we report on a reflective based assay for early diagnosis of BM through the analysis of NAGase inherent content found in whole milk samples using a miniaturized optical transducer. Gelatin functionalized porous Si Fabry–Pérot interferometers are employed for monitoring the lysosomal activity in various stages of the inflammation (healthy, subclinical and clinical). The enzymatic reaction products precipitate and accumulate within the porous nanostructure, thus alter the average refractive index monitored using reflectometric interference spectroscopy. The optical assay is calibrated within the clinically relevant concentrations of BM while presenting a dynamic range of 1.04–16.7 μM min−1 and the detection limit of 0.49 μM min−1. The specific optical performance of the biosensor correlates with a gold standard laboratory-based approach, in which escalated somatic cell counts reveal augmented NAGase levels and thus severe pathogenesis. Overall, our study provides new opportunities to develop a convenient bio-diagnostic sensing system for BM detection and classification by addressing the limitations of conventional practices.

NAD(P)H-dependent thioredoxin-disulfide reductase TrxR is essential for tellurite and selenite reduction and resistance in Bacillus sp. Y3.

Microbial reduction of selenite [Se(IV)] and tellurite [Te(IV)] to Se(0) and Te(0) can function as a detoxification mechanism and serve in energy conservation. In this study, Bacillus sp. Y3 was isolated and demonstrated to have an ability of simultaneous reduction of Se(IV) and Te(IV) during aerobic cultivation, with reduction efficiencies of 100% and 90%, respectively. Proteomics analysis revealed that the putative thioredoxin disulfide reductase (TrxR) and sulfate and energy metabolic pathway proteins were significantly upregulated after the addition of Se(IV) and Te(IV). qRT-PCR also showed an increased trxR transcription level in the presence of Se(IV) and Te(IV). Compared with a wild-type Escherichia coli strain, the TrxR-overexpressed E. coli strain showed higher Se(IV) and Te(IV) resistance levels and reduction efficiencies. Additionally, the TrxR showed in vitro Se(IV) and Te(IV) reduction activities when NADPH or NADH were present. When NADPH was used as the electron donor, the optimum conditions for enzyme activities were pH 8.0 and 37°C. The Km values of Te(IV) and Se(IV) were 16.31and 2.91mM, and the Vmax values of Te(IV) and Se(IV) were 12.23 and 11.20 µM min-1 mg-1, respectively. The discovery of the new reductive enzyme TrxR enriches the repertoire of the bacterial Se(IV) and Te(IV) resistance and reduction mechanisms. Bacillus sp. Y3 can efficiently reduce Se(IV) and Te(IV) simultaneously. Strain Y3 provides potential applications for selenite and tellurite bioremediation. The TrxR enzyme shows high catalytic activity for reducing Se(IV) and Te(IV). The discovery of TrxR enriches the bacterial Se(IV) and Te(IV) reduction mechanisms.

All fiber-optic temperature sensor based on cladding etched no-core fiber coated with nanostructured copper oxide-polyvinyl alcohol thin film

The demonstration of an interferometric temperature sensor based on a no-core fiber (NCF) with a thin layer of copper oxide-polyvinyl alcohol (CuO-PVA) coating is presented in this paper. The sensing principle relies on the multimode interference (MMI) effect that occurs in a pure silica multimode fiber (MMF) sandwiched between two single-mode fibers (SMFs), where the MMF section is an NCF. To accomplish high sensitivity, the cladding of the NCF was chemically etched at a rate of ∼2.84 μm min−1 until it reached a diameter of 18 μm. Then a thin film of CuO-PVA was coated onto the etched region to act as the sensitive cladding layer, whose refractive index (RI) varies with the environmental temperature variation. The effective interaction between the CuO-PVA and the strong evanescent field of the etched NCF results in temperature sensing with a maximum resonant wavelength shift of 21.5 nm. The maximum sensor sensitivity obtained was 0.101 nm/°C with a linear coefficient of 99.1 % in the range of 25 °C to 235 °C. To the best of our knowledge, this is the first demonstration of a temperature sensor based on an etched NCF coated with CuO-PVA thin film. This work presents an important step to enhance the performance of an all optical temperature sensor in terms of sensitivity and repeatability.

Precipitation of hydrogen peroxide during winter storms and summer typhoons

Hydrogen peroxide (H2O2) affects the activity of microbes, including archaea, and thereby influences the biogeochemical cycles of critical elements in marine and terrestrial environments. In this study, we measured the levels of H2O2 associated with three classes of extreme wet precipitation events: winter storms, tropical storms, and typhoons. In conjunction with precipitation data, the measured H2O2 concentration in a seawater reservoir receiving precipitation was used to estimate rainwater H2O2 concentration and flux. The rainwater H2O2 concentration during winter storms and coexisting storms (storms having combined maritime and continental origins) was a factor of 2–3 higher than the levels observed during the typhoons. Fluxes of H2O2 in rainwater of 6 μM min−1 or greater resulted in H2O2 concentrations ~1 μM in the seawater reservoir. During all precipitation events, the H2O2 concentration in the seawater reservoir was dominated by wet precipitation and reached levels greater than would be produced in situ by photochemical processes. During winter and coexisting storms, the rainwater H2O2 concentrations were likely to have been enhanced by atmospheric photochemical reactions probably involving pollutants. An increase in the H2O2 concentration in surface aqueous environments during extreme precipitation events will directly affect the microbial cycling of nitrogen and organic carbon.

Direct electro-co-deposition of Ni-reduced graphene oxide composite coating for anti-corrosion application

A composite coating was fabricated by electrodeposition of Ni together with electrophoresis of reduced graphene oxide (rGO) on low carbon steel. To this end, graphene oxide (GO) was first reduced chemically to rGO in order to improve electrophoretic movement. The electro-co-deposition process of Ni2+ and rGO exhibited a fast growth rate of ~3.33 µm min−1, resulting in a fine and uniform microstructure. Thus, polarization and impedance test results in 0.5 M H2SO4 suggested that Ni-rGO coating was able to provide a protection efficiency of 99.5%. Relative to other coating systems, Ni-rGO may present itself as a cost-effective, high-performance material candidate for anti-corrosion coating.

Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation.

The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min-1 , which is two orders of magnitude faster than the α and β phases.

Light‐Driven Crawling of Molecular Crystals by Phase‐Dependent Transient Elastic Lattice Deformation

AbstractThe light‐driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase‐dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ‐formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min−1, which is two orders of magnitude faster than the α and β phases.

Effect of alkaline etching on microstructure and anticorrosion performance of anodic film on Al-Mg-Si alloy

Alkaline etching as an anodization pretreatment process is critical to structure and anticorrosion performance of the anodic film. The effects of modification by alkaline etching on AA6061 surface microstructure and corresponding film growth behaviors have been investigated in this work. The in-situ characteristics of grain boundaries, intermetallic particles and film structure were investigated. It is found that a suitable etching time can effectively remove a number of intermetallic particles and reduce the roughness from the matrix surface. For 60s etching, as the microstructures (e.g. cathodic Al-Fe-Si-Mn phase, grain boundary and anodic Al-Mg-Si phase) with different local potential from the matrix are modified, the growth rate can reach 0.39μm min−1 and the integrity of the anodic film are all increased. Extending etching time up to 120s will significantly disturb the regularity of pore order and reduce film growth rate because of the excessive corrosion at grain boundary.

Purification and characterization of a novel fenamiphos hydrolysing enzyme from Microbacterium esteraromaticum MM1

Fenamiphos is a neurotoxic organophosphorus pesticide used widely to control pests of crops. Fenamiphos and its toxic oxidation products have been detected in surface and groundwaters. A novel enzyme capable of hydrolysing P–O–C bond of fenamiphos is purified from Microbacterium esteraromaticum MM1 total cellular protein using a combination of methods. The purified fenamiphos hydrolysing enzyme (FHE) was identified as enolase (phosphopyruvate hydratase), a housekeeping enzyme with molecular mass and pI value of 45 kDa and 4.5, respectively. The optimum pH and temperature for the activity of the FHE are 7 and 25 °C, respectively. We studied the influence of metal ions and inhibitors on the enzyme activity. The enzyme was strongly activated by Mg2+ whereas Hg2+ and phenylmethyl sulfonyl fluoride (PMSF) inhibited the enzyme. The kinetic parameters, Km and Vmax for fenamiphos hydrolysis were estimated to be 584.15 ± 16.22 μM and 6.46 ± 0.13 μM min−1, respectively. The FHE was functionally active against its original substrate (2-phosphoglycerate) with Km value of 5.82 ± 1.42 μM and Vmax of 4.2 ± 0.1 μM min−1. This enzyme has great potential for its application in the detoxification of fenamiphos and its warfare homologs. To our knowledge, this is the first report on the purification of fenamiphos hydrolysing enzyme.

Compaction Dynamics during Progenitor Cell Self-Assembly Reveal Granular Mechanics

Summary We study the self-assembly dynamics of human progenitor cells in agarose microwells that are used for production of chondrogenic organoids. Using image analysis on time-lapse microscopy, we estimate the aggregate area in function of time for a large number of aggregates. In control conditions, the aggregate radius follows an exponential relaxation that is consistent with the dewetting dynamics of a liquid film. Upon introducing Y-27632 Rho kinase inhibitor, the compatibility with the liquid model is lost, and slowed-down relaxation dynamics are observed. We demonstrate that these aggregates behave as granular piles undergoing compaction, with density relaxation that follows a stretched exponential. Using simulations with an individual cell-based model, we construct a phase diagram of cell aggregates that suggests that the aggregate in presence of Rho kinase inhibitor approaches glass transition.

Silicon wafer etching by pulsed high-power inductively coupled Ar/CF4 plasma with 150 kHz band frequency

A silicon wafer etching using a burst pulse high-power inductively coupled plasma (ICP) is investigated. A 200 μs wide burst of a 157 kHz power supply is employed to generate ICP with a repetition rate of 50 Hz. A rectangular pulsed voltage synchronized with the burst power supply is applied upto 1 kV at the wafer. Mixed gas of argon (Ar) and tetrafluoromethane (CF4) is supplied into the vacuum chamber. The plasma density and electron temperature are 1019 m−3 and 2.8 eV where the wafer is, respectively. In the case of Ar plasma, the silicon etching rate is 0.01 μm min−1 with 1000 V negative bias. The etching rate increases to 0.23 μm min−1 by adding CF4 into Ar and increases linearly with increasing the bias voltage. The target current and emission intensity of Ar+ and F* are depended on bias voltage from −300 to −1000 V. The etching rate sharply increases by increasing CF4 content from 0% to 10%, and it becomes almost constant at 10%. The dependency of emission intensity of F* on CF4 content is similar to the dependency the etching rate.

Degradation of the emerging concern pollutant ampicillin in aqueous media by sonochemical advanced oxidation processes - Parameters effect, removal of antimicrobial activity and pollutant treatment in hydrolyzed urine

This work presents the degradation of ampicillin (a highly consumed β-lactam antibiotic) in aqueous media by sonochemical advanced oxidation processes. Initially, effects of frequency, power and operation mode (continuous vs. pulsed) on the antibiotic degradation by sonochemistry were analyzed. Then, under the suitable operational conditions, pollutant degradation and antimicrobial activity (AA) evolution were monitored. Afterwards, computational calculations were done to establish the possible attacks by the hydroxyl radical to the ampicillin structure. Additionally, the antibiotic degradation in synthetic hydrolyzed urine by ultrasound was performed. Finally, the combination of sonochemistry with Fenton (sono-Fenton) and photo-Fenton (sono-photo-Fenton) was evaluated. Our research showed that ampicillin removal was favored at low frequency, high power (i.e., 375 kHz, 24.4 W) and continuous mode (exhibiting an initial degradation rate of 0.78 μM min−1). Interestingly, ampicillin degradation in the hydrolyzed urine by sonochemistry alone was favored by matrix components (i.e., the pollutant showed a degradation rate in urine higher than in distilled water). The sonochemical process decreased the antimicrobial activity from the treated water (100% removal after 75 min of treatment), which was related to attacks of hydroxyl radical on active nucleus (the computational analysis showed high electron density on sulfur, oxygen and carbon atoms belonging to the penicillin core). Sono-photo-Fenton system achieved the fastest degradation and highest mineralization of the pollutant (40% of organic carbon removal at 180 min of treatment). All these aspects reveal the good possibility of sonochemical advanced oxidation technologies application for the treatment of antibiotics even in complex aqueous matrices such as hydrolyzed urine.

Formation of nanosized relief on PbTe and Pb1−xSnxTe substrates surface during nonabrasive chemical–mechanical polishing by (H2O2 + HBr + ethylene glycol)/glycerol etchant compositions

The process of cutting, mechanical and chemical treatment of the PbTe and Pb1−xSnxTe crystal surface has been studied. The dependences of the chemical–mechanical polishing rate versus the dilution of the basic polishing etchant H2O2 + HBr + ethylene glycol by the glycerol have been determined. The etchant compositions are selected to implement controllable removal of semiconductors layers at a rate of 1–185 μm min−1, with such quality of the single crystals surface that allows the subsequent procedures specified by planar technology and the microscopic structural studies. The surface states after chemical etching have been investigated using electron, metallographic and atomic force microscopy. Using X-ray microanalysis, we have monitored the concentrations of the host elements (Pb and Te) and possible contamination with chemical compounds present in the etchants and the solutions used to rinse the samples. It was shown that the surface state is improved after chemical etching.

Predicting Confined 1D Cell Migration from Parameters Calibrated to a 2D Motor-Clutch Model

Biological tissues contain micrometer-scale gaps and pores, including those found within extracellular matrix fiber networks, between tightly packed cells, and between blood vessels or nerve bundles and their associated basement membranes. These spaces restrict cell motion to a single-spatial dimension (1D), a feature that is not captured in traditional in vitro cell migration assays performed on flat, unconfined two-dimensional (2D) substrates. Mechanical confinement can variably influence cell migration behaviors, and it is presently unclear whether the mechanisms used for migration in 2D unconfined environments are relevant in 1D confined environments. Here, we assessed whether a cell migration simulator and associated parameters previously measured for cells on 2D unconfined compliant hydrogels could predict 1D confined cell migration in microfluidic channels. We manufactured microfluidic devices with narrow channels (60-μm2 rectangular cross-sectional area) and tracked human glioma cells that spontaneously migrated within channels. Cell velocities (vexp = 0.51 ± 0.02 μm min−1) were comparable to brain tumor expansion rates measured in the clinic. Using motor-clutch model parameters estimated from cells on unconfined 2D planar hydrogel substrates, simulations predicted similar migration velocities (vsim = 0.37 ± 0.04 μm min−1) and also predicted the effects of drugs targeting the motor-clutch system or cytoskeletal assembly. These results are consistent with glioma cells utilizing a motor-clutch system to migrate in confined environments.

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Summary Highly crystalline and emissive carbon dots (CDs) are firstly synthesized via an ionothermal method in organic solvents. In contrast to well-established approaches, ZnCl2 is utilized as the pyrolysis-promoting agent to prepare emissive CDs with tunable wavelengths, directly by carbonization from different O and N precursors under a mild reaction condition at 210°C. More than 50% synthetic yield and 39% photoluminescent quantum yield (blue CD) are obtained. XAFS measurements, in conjunction with TEM, HAADF-STEM, UPS, and ESR analyses, allow us to obtain energy diagram configuration and confirm the luminescent nature of these hard-core structured CDs. Importantly, the resulting CDs exhibit excellent capability to photogenerate superoxide radical anion (O2⋅–), which can be exemplified by both photodynamic therapy and photooxidative cyclization synthesis of tetrahydroquinolines. Representative pharmaceutical mifepristone can be derivatized in 90% yield within 10 min of irradiation of the CDs in an elegant flow reactor.

Characterization of EstZY: A new acetylesterase with 7-aminocephalosporanic acid deacetylase activity from Alicyclobacillus tengchongensis

Deacetyl-7-aminocephalosporanic acid (D-7-ACA) is required for producing of many semisynthetic β-lactam antibiotics; therefore, enzymes capable of converting 7-aminocephalosporanic acid (7-ACA) to D-7-ACA present a valuable resource to the pharmaceutical industry. In the present study, a putative acetylesterase, EstZY, was identified and characterized from a thermophilic bacterium Alicyclobacillus tengchongensis. Sequence alignment showed that EstZY was an acetylesterase which belonged to carbohydrate esterase family 7 (CE7), with substrate preference for short-chain acyl esters p-NPC2 to p-NPC8. Maximum enzyme activity was recorded at pH 9.0 and 50 °C, where Km and Vmax were calculated as 1.9 ± 0.23 mM and 258 ± 18.5 μM min−1, respectively. The residues Ser185, Asp274, and His303 were identified as the putative catalytic triad by homology modelling, site-directed mutagenesis and molecular docking. Moreover, EstZY can remove the acetyl group at C3′ position of 7-ACA to form D-7-ACA; this is the first report of a 7-ACA deacetylase from CE7 family in A. tengchongensis and may represent a new enzyme with industrial values.

An Inorganic Biopolymer Polyphosphate Controls Positively Charged Protein Phase Transitions.

Polyphosphate (PolyP) is one of the most compact inorganic polyanionic biopolymers that participates in various physiological processes. However, the mechanism of the interaction between polyP and proteins remains poorly understood. Herein, we report that polyP can interact with positively charged green fluorescent protein, +36GFP, resulting in liquid-liquid phase separation (LLPS) by intermolecular electrostatic interactions in cells. Upon nutrient deprivation, genetically engineered Citrobacter freundii accumulates intracellular polyP at a rate of 210 μm min-1 , resulting in the compartmentation of +36GFP at the cell poles within 1 h. Medium chain-length polyP (60-mer) could induce the formation of +36GFP coacervates in vitro at a protein concentration as low as 200 nm, which is of the same magnitude as native proteins. In contrast, shorter polyP (14-mer) could not induce LLPS under the same conditions. This may offer a general approach to manipulate protein-protein interactions through LLPS.