MPa Pressure Research Articles

Effect of Mn addition in W-Ni-Cu heavy alloy processed through hot press sintering techniques on microstructure, microtexture and grain boundary character evolution

In this current study, the impact of manganese addition to 93 W-4.9Ni-2.1Cu-xMn (where x = 1, 2, 3, and 4 Wt%) on the microstructure, texture development, and grain boundary character distribution of tungsten heavy alloy (WHAs) was examined. The samples were produced through a vacuum hot press sintering, with parameters 50 MPa pressure, 10 °C/min heating rate, and 1450 °C sintering temperature for 20 min holding duration. To study the influence of manganese on the texture development and microstructure in conventional WHAs, electron backscatter diffraction (EBSD) was employed. The important findings from the EBSD analysis reveal that fibre texture (001) 〈111〉 and a higher fraction of low-angle grain boundaries in the Mn unalloyed compact resulted from extensive atomic jumps between the particles at elevated temperatures. Further texture analysis on the Mn-added compacts reveals that manganese oxide (MnO) formation during liquid phase sintering led to lower densification and randomized weak fibre texture development in manganese-alloyed compacts. In addition, the texture degradation in Mn-added compacts is mainly caused by recrystallization followed by sub-structural recovery during liquid phase sintering. This study indicates that increasing manganese content in WHAs stoichiometry led to a heterogeneous distribution of binder matrix (NiCu) in the sintered compact. As a result, W-4.9Ni-2.1Cu-4Mn alloy revealed decreased relative density (90.70%), microhardness (389.5 HV0.5), and electrical conductivity (15.74% of IACS).

Liquid-phase hydrogenation of sunflower oil over platinum and nickel catalysts: Effects on activity and stereoselectivity

This study presents the results of comparative hydrogenation of sunflower oil over a platinum catalyst supported on activated diatomite and an industrial nickel catalyst (Pricat-9910). Catalysts are characterized using physical methods, such as transmission electron microscopic, temperature programmed hydrogen desorption, Brunauer–Emmett–Teller and inductively coupled plasma atomic emission spectrometry, enabling the determination of the size of catalyst particles, forms of adsorbed hydrogen, and specific surface area. Depending on the process conditions, hydrogenation reaction rates on platinum catalysts have been found to be 2–5 times higher than cis-trans isomerization reaction rates. Using a nickel catalyst, the hydrogenation and isomerization rates at low temperatures (110°C-130 °C) and 0.5 MPa pressure are almost similar, while, the hydrogenation rate is 1.4–1.8 times lower than the isomerization rate at high temperatures and pressures, leading to the formation of a large number of trans isomers. The difference in catalysts selectivity may be attributed the speciation and different adsorption energies of surface hydrogen, leading to the possibility of simultaneous hydrogenation of linoleic and oleic acids on the nickel catalyst.

Performance of laminated veneer lumber panels from fast-growing species with different layering arrangements

This study investigated the effect of various layer arrangements and their impact on the properties of laminated veneer lumber (LVL). Seven different layer arrangements (CCCCCCC, DDDDDDD, PPPPPPP, CDDDDDC, CPPPPPC, CDDCDDC, CPPCPPC, CDCDCDC, CPCPCPC, CCDDDCC, CCPPPCC, CCDCDCC, and CCPCPCC) were used in the manufacturing of the LVL, with each arrangement represented by a combination of the three wood species: hornbeam (C), paulownia (P), and poplar (D). The veneers were bonded with a polyurethane adhesive and pressed under 1 MPa pressure. The physical and mechanical properties of the laminated veneer lumber, including modulus of rupture, modulus of elasticity, block shear, delamination, and swelling, were measured under both dry and cyclic conditions (boil and dry). The modulus of rupture and modulus of elasticity of the LVLs increased when the proportion of hornbeam in the lamination increased. In the cyclic boil-dry condition, the laminated veneer lumbers with the configurations CPCPCPC and CDCDCDC showed the best structural performance. Furthermore, the study found that when one or two upper layers of poplar and paulownia were replaced with hornbeam layers, cracks were observed in the laminated veneer lumber samples. However, when the layers of poplar and paulownia were replaced with hornbeam alternately, no cracks were observed after saturating the laminated veneer lumber with water. The utilization of an alternating arrangement of poplar and paulownia layers with hornbeam in LVL can be used as an effective and cost-efficient approach for enhancing and reinforcing the LVL performance.

Densification of hydroxyapatite through cold sintering process: Role of liquid phase chemistry and physical characteristic of HA powder

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Study on Oxidation Activity of Hydrogenated Biodiesel–Ethanol–Diesel Blends

In the pursuit of understanding the oxidation mechanisms of hydrogenated biodiesel fuels and elucidating the combustion behavior of biomass fuels when blended with diesel, this study presents a comprehensive investigation into the reaction mechanism of hydrogenated biodiesel–ethanol–diesel mixtures. We develop a comprehensive reaction mechanism encompassing 187 components and 735 reactions for hydrogenated biodiesel–ethanol–diesel mixtures. Through kinetics analysis under varied conditions, including 1.0 MPa pressure, an equivalence ratio of 1.0, and temperatures of 900 K and 1400 K, we explore the impact of cross-reactions and changing fuel blend ratios on low- and high-temperature oxidation. Our findings indicate that oleic and stearic acid methyl esters serve as better substitutes for representing hydrogenated biodiesel kinetics than methyl decanoate. At lower temperatures, increased hydrogenated biodiesel and ethanol content leads to reduced OH generation, impacting reactivity. Conversely, higher temperatures result in enhanced OH production with increased hydrogenated biodiesel and ethanol concentrations, promoting reactivity. A cross-reaction analysis reveals CH2O as a prominent product, with the CH2O→HCO→CO pathway playing a pivotal role. In summary, our research unveils the intricate oxidation mechanisms of hydrogenated biodiesel–ethanol–diesel mixtures, providing insights into their combustion characteristics and offering implications for optimizing fuel blends for cleaner and more efficient energy solutions.

Tracking contaminants in the aqueous effluent during supercritical water gasification and oxidation of swine manure in the flow mode

Biomass waste processing is an area of great interest due to its potential for reducing environmental impact and recovering resources. The present work investigates for the first time the composition of products resulting from supercritical water (SCW) gasification and oxidation of swine manure (SM) continuously fed into a tubular reactor at a temperature gradient along its vertical axis of 390–600 °C and a pressure of 25 MPa. Special attention is paid to how the operating parameters, including SM flow rate (6.5–10.7 g/min), oxidation ratio (OR ≤ 1.78), and the presence of NaOH additive (1 wt%) influenced the composition and concentration of contaminants (phenols, N-bearing aromatics, polyaromatic hydrocarbons (PAHs), and ammonia) in the effluent collected at the reactor outlet. The results of gas chromatography-mass spectrometry indicate that water-soluble products comprise predominantly of phenols, pyridines, pyrroles, indoles, pyrazines, anilines, and quinolines. Increasing the reagent’s residence time during SCW gasification was observed to lower the amount of phenols in the effluent. In addition, the introduction of NaOH increases the yields of syngas and NH3 while lowering the concentration of N-bearing aromatics and PAHs. SCW oxidation of SM not only reduces contaminant levels in the effluent by several orders of magnitude, but also partially compensates for thermal inputs needed for the process implementation. Among N-bearing compounds, ammonia, pyridines, indoles, and quinolines display the highest resistance to oxidation. The paper explores the resource-saving and ecological benefits of SCW gasification and oxidation of SM.

Silicone and nano-diamond modified graphene oxide anticorrosive coating

Graphene oxide (GO) has abundant oxygen-containing functional groups, making it easy to undergo covalent and non-covalent modifications, coupled with its excellent physical barrier ability, which shows great prospects in improving the corrosion resistance of coatings. Unfortunately, GO has a strong van der Waals force and π-π interactions, which make it prone to self-aggregation, and at the same time, in the process of preparing the coating due to the volatilization of solvents, it is easy to produce micropores and other defects, which will not be conducive to the long-term corrosion resistance of the coating. Therefore, this work used silicone as a “bridge” to modify GO with nanodiamond, and then a composite coating with excellent anticorrosion properties was prepared with vinyl ester resin under heating conditions. This work not only effectively solved the dispersion and interface interaction of GO in the resin, but also the diluent in this process could fully participate in the polymerization reaction, effectively avoiding the volatilization of volatile gases. The results showed that the conductivity of the modified GO reached the level of the insulating material (9.6 × 10−9 S/cm, 30 MPa pressure). Electrochemical tests showed that the |Z|0.01Hz value of the coating was as high as 1.00 × 109 Ω cm2 after soaking in 3.5 wt% brine for 120 days, which was three orders of magnitude higher than the control group. Compared to the control group, the protective efficiency of the coating remained at 97.8 %. This was mainly related to the synergistic anticorrosion effect of GO and nano-diamond. In short, this work provided a new research approach for the preparation of long-lasting anticorrosion coatings using zero-dimensional and two-dimensional materials.

An ultrasonic study of the effect of uniaxial green compaction pressure on the elastic anisotropy of porous copper fabricated using the pore-former route

Porous copper is potentially very attractive for various functional applications such as filters and heat exchanger materials. Within the scope of this study, porous copper samples with dual pore morphologies were fabricated following the space holder technique using a 1:2 mixture ratio of K2CO3 to NaCl as pore formers. The initial compaction pressure required for green body fabrication was systematically varied between 120 and 180 MPa, and the influence of this pressure over porosity, pore morphology, volume shrinkage, and longitudinal elastic constants was systematically studied. Three longitudinal elastic constants of the porous Cu samples were determined following the non-destructive ultrasonic phase spectroscopy method through the measurement of the phase shift vs. frequency spectra along the three orthogonal directions in each sample. When the applied pressure is increased from 120 to 160 MPa and the Cu:PF mixture ratios are 70:30 and 60:40, respectively, the elastic constant values in the green compaction direction (C11) decrease from 34.2 GPa to 7.5 GPa and 23.7 GPa–17.9 GPa. However, for Cu:PF mixture ratios of 70:30 and 60:40, under 180 MPa green compaction pressure C11 increases to 30.9 GPa and 21.2 GPa, respectively. As the applied green compaction pressure increased from 120 to 160 MPa, the samples' average elastic anisotropy ratio initially increased from 0.29 to 0.59 and then decreased to 0.55 at 180 MPa pressure. While the initial increase in anisotropy is due to increased pore flattening with increasing green compaction pressure, the decrease in anisotropy ratio in the samples fabricated under 180 MPa green compaction pressure is due to enhanced sample densification. Contour maps for different properties have been proposed to identify the optimum combination of initial powder composition and green compaction pressure for the intended end application.

Effect of particle volume fraction on wear behavior in Al–SiC MMC coated on DIN AlZnMgCu1.5 alloy

Abstract In this study, DIN AlZnMgCu1.5 alloy surface (Al + SiC) was coated with metal matrix composite (MMC) by using hot press sintering method (HPSM). Al was used as matrix material and SiC powders were used as reinforcing material in the coating process on DIN AlZnMgCu1.5 alloy surface. Al/SiC MMC coating was produced at 600 °C under 120 MPa pressure and with varying SiC content (5, 10 and 15 vol.%). Optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to examine the microstructure, elemental analysis and phase structure of both the coating zone and the transition zone between the substrate and the coating. The hardness was measured and a dry sliding linear reciprocating wear test was run to determine the mechanical properties of the coating layer. Consequently, the coefficient of friction (COF) and wear volume were determined. OM and SEM images showed a homogeneous distribution of SiC particles and a less porous structure. The hardness of the MMC coating increased with increasing SiC content. Also, the numerical analysis of the wear test simulation was done based on Archard’s law. The results of both wear tests showed that the volume loss values were consistent with each other and the amount of wear significantly reduced by increasing the rate of SiC reinforcement.

Major improvements in the WCLL TBM design towards next review gates

The European domestic agency (Fusion for Energy) is developing the WCLL-TBS (Water Cooled Lithium Lead Test Blanket System) concept for its implementation and testing in ITER. The system is based on the use of the eutectic Pb–15.7Li enriched at 90 % in 6Li as tritium breeder and tritium carrier. Water is used as coolant with current target nominal inlet/outlet temperatures of 295/328 °C and 15.5 MPa pressure (similar to PWR conditions). The Test Blanket Module –TBM– is the in-vessel component where tritium generation will take place and whose structural material is EUROFER 97. Its design has been significantly improved in the last years. These design improvements have focused on three major areas: (i) overcoming some weaknesses of the previous design in the rear manifold area associated to the stiffening rod concept, (ii) strengthening the link with manufacturing developments and (iii) optimizing the amount of EUROFER 97 in the TBM box, so that the design converges to the limits imposed by the ITER project requirements. The work presented in this paper describes the latest design evolutions achieved in the WCLL TBM design with respect to that presented at CDR and, in particular, the major re-design of the TBM in the manifold area based on the ‘crossing vertical’ stiffening plate concept proposed and developed by the ESTEYCO Mechanics design team in collaboration with F4E.

Synthesis of hydroxyapatite matrix Ag and CNT particle reinforced hybrid biocomposites with improved mechanical and antibacterial properties

Abstract Hydroxyapatite is an important biomaterial for orthopaedic applications due to its high structural similarity to human bone. However, weak mechanical and antibacterial properties limit the use of hydroxyapatite compared to metallic implants such as Ti and 316L alloys for direct use in the human skeleton. To overcome these shortcomings, we have prepared hydroxyapatite matrix silver and carbon nanotube reinforced biocomposites. Silver particles have beneficial effects on biomaterials due to their effective antibacterial activity. In addition, CNT particles are known for their high strength and their ability to improve the mechanical properties of composite materials. To prepare the hydroxyapatite-based composites, the powder blends with different reinforcement types (Ag, CNT) and ratios were ground using a planetary ball mill. The biocomposite powders were then cold pressed under 500 MPa pressure to obtain green samples. The sintering process was carried out at 1200 °C for 4 h. The microstructural and structural investigations were carried out by scanning electron microscopy and X-ray diffraction, respectively. In order to better evaluate the mechanical properties of the samples, hardness measurements, compression and fracture tests were carried out. Antibacterial tests were also carried out against various micro-organisms. Both types of reinforcement were found to be effective in improving the mechanical properties. In addition, it was observed that CNT reinforcement slightly increased the antibacterial resistance, but silver-reinforced samples provided excellent antibacterial resistance.

Experimental study of precursory features of CO2 blasting-induced coal rock fracture based on grayscale and texture analysis.

CO2 blasting has been identified as a potent method for enhancing the permeability of coal seams and improving gas drainage efficiency. This study is focused on elucidating the deformation and fracture mechanisms of coal and rock during CO2 blasting and on identifying the precursor characteristics of these processes. To this end, a CO2 blasting-induced coal rock fracture pressure model and a gas pressure distribution model were developed. The research utilized a self-developed CO2 blasting test platform along with a non-contact full-strain field measurement analysis system. Briquette samples were subjected to CO2 blasting tests under controlled experimental conditions, which included an axial pressure of 1.0 MPa and variable gas pressures of 0.5, 1.0, and 1.5 MPa. This methodology enabled the capture of the principal strain field on the surface of the samples. The Gray Level Co-occurrence Matrix (GLCM) was employed to extract and analyze the grayscale and texture features of the strain cloud maps, facilitating a quantitative assessment of their evolution. The aim was to pinpoint the precursor characteristics associated with coal rock cracking and crack propagation. The results revealed that: (1) During the cracking and subsequent propagation of samples, the strain field's grayscale histogram underwent a transformation from a "broad and low" to a "narrow and high" configuration, with a consistent increase in peak frequency. Specifically, at 3 ms, a primary crack was observed in the sample, evidenced by a grayscale peak frequency of 0.0846. By 9 ms, as the crack propagated, the grayscale peak frequency escalated to 0.1626. (2) The texture feature parameters experienced their initial abrupt change at 3ms. Correlation with the gas pressure distribution model indicated that this was the crack initiation moment in the sample. (3) A secondary abrupt shift in the texture feature parameters occurred at 9ms, in conjunction with experimental phenomena, was identified as the crack propagation phase. Monitoring the grayscale and texture features of the principal strain field on the coal rock surface proved effective in recognizing the precursor characteristics of crack initiation and propagation. This research has the potential to reduce blasting costs in coal mines, optimize blasting effects, and provided theoretical guidance for enhancing gas extraction efficiency from deep and low permeability coal seams.

Measurements of the Effective Stress Coefficient for Elastic Moduli of Sandstone in Quasi-Static Regime Using Semiconductor Strain Gauges.

Numerous experimental and theoretical studies undertaken to determine the effective stress coefficient for seismic velocities in rocks stem from the importance of this geomechanical parameter both for monitoring changes in rock saturation and pore pressure distribution in connection with reservoir production, and for overpressure prediction in reservoirs and formations from seismic data. The present work pursues a task to determine, in the framework of a low-frequency laboratory study, the dependence of the elastic moduli of n-decane-saturated sandstone on the relationship between pore and confining pressures. The study was conducted on a sandstone sample with high quartz and notable clay content in a quasi-static regime when a 100 mL tank filled with n-decane was directly connected to the pore space of the sample. The measurements were carried out at a seismic frequency of 2 Hz and strains, controlled by semiconductor strain gauges, not exceeding 10-6. The study was performed using a forced-oscillation laboratory apparatus utilizing the stress-strain relationship. The dynamic elastic moduli were measured in two sets of experiments: at constant pore pressures of 0, 1, and 5 MPa and differential pressure (defined as a difference between confining and pore pressures) that varied from 3 to 19 MPa; and at a constant confining pressure of 20 MPa and pore pressure that varied from 1 to 17 MP. It was shown that the elastic moduli obtained in the measurements were in good agreement with the Gassmann moduli calculated for the range of differential pressures used in our experiments, which corresponds to the effective stress coefficient equal to unity.

In situ observation of a macrourid fish at 7259 m in the Japan Trench: swimbladder buoyancy at extreme depth.

A macrourid, Coryphaenoides yaquinae sp. inc., was observed to be attracted to bait and exhibiting normal foraging behaviour during a period of 80 min within view of a baited video camera on the sea floor at 7259 m - the deepest ever observation of a fish species with a swim bladder. The buoyancy provided by an oxygen-filled swim bladder at 74.4 MPa pressure was estimated to be 0.164N, at a theoretical energy cost of 20 kJ, 200 times less than the cost of equivalent lipid buoyancy. During normal metabolism, 192 days would be required to fill the swimbladder. At these depths, oxygen is very incompressible, so changes in volume during ascent or descent are small. However, swimbladder function is crucially dependent on a very low rate of diffusion of oxygen across the swimbladder wall. The oxygen in the swimbladder could theoretically sustain aerobic metabolism for over 1year but is unlikely to be used as a reserve.

Daqing Oilfield Cable Controlled Intelligent Separate Injection Technology Process Optimization

The cable controlled intelligent separate injection process realizes the continuous monitoring and real-time measurement and adjustment of downhole parameters, greatly improves the measurement and adjustment efficiency, provides sufficient data for reservoir analysis, and helps to tap the potential of remaining oil in the later stage of ultra-high water cut. However, due to the multi-disciplinary application of downhole tools and complex process, it is found in the previous field test that The number of wells with more than two years of operation of cable controlled intelligent separate injection wells accounts for only 51.9%, which can not meet the needs of large-scale application. Through the fault analysis of the early test well, the key factors affecting the success rate of well completion are found. Aiming at the main problems, the flow control valve of the cable controlled intelligent water distributor, the cable sealing connection process and the well flushing valve structure through the cable packer are optimized and improved. The flow control valve of cable controlled intelligent water distributor is opened and closed smoothly under 10MPa pressure difference, and the leakage is less than 1m³/d; The connection between the cable and the cable controlled intelligent water distributor is sealed reliably, and the cable can pass through the upper and lower joints of the cable packer smoothly; Since the optimization of process technology until January 2023, 223 wells have been tested on site, and the number of wells with more than two years of operation has increased from 56.1% to 91.9%. The stability of the optimized cable controlled intelligent separate injection process has been improved, which lays a foundation for the large-scale application of this technology in the oilfield.

Density and viscosity modeling of liquid adipates using neural network approaches

Liquid Dialkylesters of adipic acid (adipates) have achieved prominence as alternative green solvents due to their special properties. To enhance their utilization, accurate thermophysical property data are required, especially for extended pressure ranges. This study presents the application of Artificial Neural Networks (ANNs) for predicting the densities and viscosities of liquid adipates over a wide range of temperatures and pressures. A substantial dataset, including 1145 viscosity and 891 density data points, was utilized across a broad range of temperature and pressure conditions. The dataset used for densities includes data for six different liquid adipates and covers a temperature range of 293.15–403.15 K and pressures up to 140 MPa, while the dataset used for viscosities encompasses data for four different liquid adipates, ranging from 293.15 K to 403.15 K in temperature and up to 65.62 MPa in pressure. Two ANN models were developed and fine-tuned, with two separate models created to predict the properties of liquid adipates. These models exhibited very good performance, achieving an Average Absolute Relative Deviation (AARD) of 0.028 % for density and 0.400 % for viscosity. The results from the ANN models were compared with semi-empirical models based on the equation of state and rough hard-sphere theory, showcasing the technique's potential as a powerful tool for characterizing thermophysical properties. As part of enhancing model reliability and robustness, various tests were conducted to validate the chosen model.

Research on the Tensile Mechanical Properties and Fracture Characteristics of GFRP Mortar Tubes under Impact Loads

To investigate the protective effect of glass fiber-reinforced plastic (GFRP) pipes on cement mortar, dynamic splitting tests were carried out on cement mortar and GFRP-mortar pipe specimens by using a 74 mm diameter Hopkinson pressure bar (SHPB) test device combined with a high-speed video camera device to obtain the crack expansion process and rupture and fragmentation morphology of the specimens. The results show that the tensile strength of cement mortar rings is lower and that the stress?strain curve is single-peaked. Compared with cement mortar rings, the tensile strength of GFRP-mortar ring specimens increases significantly, and the stress-strain curve is bimodal. For 0.5 MPa air pressure and wall thicknesses of 0, 2, 3, and 4 mm, the hollow rate of the 0.187 specimen peak stress is 3.21, 1.02, 1.05, and 1.26 times that of the 0.292 specimen. For 0.5 MPa air pressure and a hollow rate of 0.187, the wall thickness of the 2, 3, and 4 mm specimen peak stress is 1.06, 1.31, and 1.69 times that of the 0 mm specimen. The increase in the wall thickness, the decrease in the hollow rate and the increase in the strain rate make the dynamic tensile strength of the specimens increase. The dynamic modulus of elasticity of the GFRP-mortar pipe specimens was lower than that of the mortar specimens, and the increase in strain rate and the thickness of the GFRP pipe wall resulted in an increase in the dynamic modulus of elasticity of the specimens. The cement mortar specimen under impact load was split and tensile damage occurred; the GFRP-mortar specimen suffered tensile damage at the two ends of the applied force, and the upper and lower ends were crushed. With the increase in the strain rate, the GFRP-mortar specimens transitioned from cracks to the formation of “V” area damage, and the specimen crushing degree increased, but the existence of GFRP pipe can have a protective effect on the mortar, reducing the degree of specimen rupture and crushing. The increase in the hollow ratio reduces the ability of the specimen to resist the external load, and the degree of specimen rupture and fragmentation increases.

Fabrication, microstructure, spectral properties, and laser performance of Yb:GdxY3−xAl5O12 ceramics

AbstractHighly transparent 10 at.% Yb:GdxY3−xAl5O12 (x = 0.3, 0.5, and 0.7) ceramics were successfully fabricated by vacuum solid‐state reactive sintering at 1800°C for 20 h combined with hot isostatic pressing posttreatment at 1700°C for 3 h under 176 MPa pressure in Ar atmosphere. The in‐line transmittances of these ceramics with the thickness of 2.5 mm are 84.4%, 84.0%, and 83.5% at 1100 nm for x = 0.3, 0.5, and 0.7, respectively. The relationships of the Gd3+ content among the phase, microstructures, spectral, and laser properties of the Yb:GdxY3−xAl5O12 ceramics were elucidated in detail. The introduction of Gd3+ has a little influence on the crystal field strength of the Yb3+ sites in GdxY3−xAl5O12. The absorption, emission spectra, and fluorescence lifetime of the Yb3+ in these ceramics are similar, close to 10 at.% Yb:YAG ceramics. Quasi‐continuous wave laser outputs of the ceramics were also achieved. The maximum laser output powers are 7.8, 7.7, and 6.6 W with the corresponding slope efficiency as 46.2%, 44.7%, and 39.2% for x = 0.3, 0.5, and 0.7, respectively. The 7.8 W laser output power is the highest value achieved so far for the Yb:GdYAG ceramics, to the best of our knowledge. The previous discussions show that not all the mixed garnets could enhance full width at half maximum of absorption and emission peaks for the active ions; however, the Yb:GdYAG ceramics are still excellent laser gain media.

Possibility of transfer and activation of 'silent' tetracycline resistance genes among Enterococcus faecalis under high-pressure processing

In this study, the tetracycline resistance of Enterococcus faecalis strains isolated from food was determined and molecular analyses of the resistance background were performed by determining the frequency of selected tetracycline resistance genes. In addition, the effect of high-pressure stress (400 and 500 MPa) on the expression of selected genes encoding tetracycline resistance was determined, as well as changes in the frequency of transfer of these genes in isolates showing sensitivity to tetracyclines. In our study, we observed an increase in the expression of genes encoding tetracyclines, especially the tet(L) gene, mainly under 400 MPa pressure. The study confirmed the possibility of transferring genes encoding tetracyclines such as tet(M), tet(L), tet(K), tet(W) and tet(O) by horizontal gene transfer in both control strains and exposed to high-pressure. Exposure of the strains to 400 MPa pressure had a greater effect on the possibility of gene transfer and expression than the application of a higher-pressure. To our knowledge, this study for the first time determined the effect of high-pressure stress on the expression of selected genes encoding tetracycline resistance, as well as the possibility and changes in the frequency of transfer of these genes in Enterococcus faecalis isolates showing sensitivity to tetracyclines and possessing silent genes. Due to the observed possibility of increased expression of some of the genes encoding tetracycline resistance and the possibility of their spread by horizontal gene transfer to other microorganisms in the food environment, under the influence of high-pressure processing in strains phenotypically susceptible to this antibiotic, it becomes necessary to monitor this ability in isolates derived from foods.

Development of a Binderless Particleboard from Brown Seaweed Sargassum spp.

Since 2010, huge quantities of Sargassum spp. algae have been proliferating in the Atlantic Ocean and stranding on Caribbean beaches, causing major economic, environmental, and health problems. In this study, an innovative high-density binderless particleboard was developed using uniaxial thermo-compression coupled with a cooling system. The raw material consisted of ground Sargassum seaweeds pre-treated by twin-screw extrusion with water to remove sea salt. The raw material and the particleboards were produced by using various analytical techniques such as Dynamic Vapor Sorption (DVS), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), or Thermogravimetric Analysis (TGA). The experimental conditions for thermo-compression (temperature, pressure, time) were evaluated. The best thermo-compression conditions tested were 200 °C, 40 MPa pressure for 7.5 min. This resulted in a particleboard with high density (up to 1.63 ± 0.02 g/cm3) and high flexural strength/modulus (up to 32.3 ± 1.8 MPa/6.8 ± 0.2 GPa, respectively), but a low water contact angle of 38.9° ± 3.5°. Thermal analyses revealed the effect of alginates on the mechanical properties of particleboards. This work opens the door to a new way of adding value to Sargassum seaweed, using the whole algae with minimal pre-treatment.