Internal Metal Research Articles

2D Metal Covalent Organic Frameworks Towards Electrochemical Catalysis

In the past century, innovative electrochemical reactions with low-consumption and environmental-friend have been a key substance for worldwide chemical industry.[1] Nowadays, the majority of the electrochemical reactions rely on low-cost and high-efficient catalysts, and there is an ever-growing need for the development of advanced catalysts to secure a sustainable future for our society.[2] The pursuit for sustainable energy stimulates the innovative concepts of advanced catalytic materials for electrochemical reactions, such as metal-air battery, nitrogen fixation and carbon neutrality etc.[3] The electrocatalysts play a vital role to promote the renewable energy conversion efficiencies and system performance.[4] However, the electrocatalytic activities of most inorganic catalysts arises from the unsaturated metal sites exposed on the surfaces or edges, and the internal metal atoms in bulk phase are totally inert, resulting in the low utilization and efficiency of metal atoms for electrocatalysis.[5] Exploring novel electrocatalysts with high metal utilization is essential for electrochemical reactions. Recently, single-atom catalysts (SACs) strategy has been proposed to promote the efficiency and utilization of metal atoms in electrocatalysts. In particular, SACs could provide an ideal approach to maximize the efficiency of active metal atom utilization (in principle, up to 100%) and lower the cost of the electrochemical reactions.[6] Inspired by SACs strategy, metal covalent-organic-frameworks (MCOFs) can be emerged as efficient catalysts, due to the numerous single-atom sites, ordered in-plane porous structure and outstanding stable framework. We propose a novel two-dimensional MCOFs, constructed by porphyrin subgroup (Figure 1), for achieving high efficiency of electrochemical reactions. Porphyrinsubgroup is a type of heterocyclic molecules with conjugated structure, which has strong ability to coordinate almost all transition metal ions to form high active single-metal sites. Thus, MCOFs with porphyrin could be a promising next-generation electrocatalyst, and an ideal catalytic model to reveal the mechanism of electrochemical reactions. Acknowledgments: The authors gratefully acknowledge the financial support from H2020 Marie Skłodowska-Curie Actions (101024758) and National Natural Science Foundation of China (22002083).

Impact of internal metal ions in tea polysaccharides on antioxidant potential and suppression of cancer cell growth

Four kinds of tea polysaccharides (MBTPS, MGTPS, ZBTPS, ZGTPS) were extracted from Maofeng black tea, Maofeng green tea,Ziyan black tea and Ziyan green tea, and then four tea polysaccharides (RMBTPS, RMGTPS, RZBTPS, RZGTPS) after metal removal were prepared. The physicochemical properties, antioxidant activity and inhibitory activity on cancer cell proliferation of the above polysaccharides were studied. The composition analysis shows that these tea polysaccharides were glycoproteins complexes, composed of a variety of monosaccharides, and the removal of metal ions did not lead to fundamental changes in the composition of polysaccharides. In vitro activity, after removing metal ions, the ABTS free radicals scavenging ability and reducing power of tea polysaccharides were decreased, and the inhibitory effect on proliferation of H22 cells weakened. There was a great correlation between metal elements Al and Ni and biological activity. The results showed that the metal ions in tea polysaccharides, especially Al and Ni, had positive effects on biological activity.

A Printable Magnetic-Responsive Iron Oxide Nanoparticle (ION)-Gelatin Methacryloyl (GelMA) Ink for Soft Bioactuator/Robot Applications.

The features or actuation behaviors of nature's creatures provide concepts for the development of biomimetic soft bioactuators/robots with stimuli-responsive capabilities, design convenience, and environmental adaptivity in various fields. Mimosa pudica is a mechanically responsive plant that can convert pressure to the motion of leaves. When the leaves receive pressure, the occurrence of asymmetric turgor in the extensor and flexor sides of the pulvinus from redistributing the water in the pulvinus causes the bending of the pulvinus. Inspired by the actuation of Mimosa pudica, designing soft bioactuators can convert external stimulations to driving forces for the actuation of constructs which has been receiving increased attention and has potential applications in many fields. 4D printing technology has emerged as a new strategy for creating versatile soft bioactuators/robots by integrating printing technologies with stimuli-responsive materials. In this study, we developed a hybrid ink by combining gelatin methacryloyl (GelMA) polymers with iron oxide nanoparticles (IONs). This hybrid ION-GelMA ink exhibits tunable rheology, controllable mechanical properties, magnetic-responsive behaviors, and printability by integrating the internal metal ion-polymeric chain interactions and photo-crosslinking chemistries. This design offers the inks a dual crosslink mechanism combining the advantages of photocrosslinking and ionic crosslinking to rapidly form the construct within 60 s of UV exposure time. In addition, the magnetic-responsive actuation of ION-GelMA constructs can be regulated by different ION concentrations (0-10%). Furthermore, we used the ION-GelMA inks to fabricate a Mimosa pudica-like soft bioactuator through a mold casting method and a direct-ink-writing (DIW) printing technology. Obviously, the pinnule leaf structure of printed constructs presents a continuous reversible shape transformation in an air phase without any liquid as a medium, which can mimic the motion characteristics of natural creatures. At the same time, compared to the model casting process, the DIW printed bioactuators show a more refined and biomimetic transformation shape that closely resembles the movement of the pinnule leaf of Mimosa pudica in response to stimulation. Overall, this study indicates the proof of concept and the potential prospect of magnetic-responsive ION-GelMA inks for the rapid prototyping of biomimetic soft bioactuators/robots with untethered non-contact magneto-actuations.

Immersion and electrochemical corrosion properties and combined corrosion mechanism of TC4 alloy by keyhole TIG welding

In this study, the effect of heat input on the microstructure and its correlation with the immersion corrosion properties of TC4 welded joints by Keyhole tungsten inert gas (TIG) process was researched. The combined corrosion mechanism between immersion corrosion and electrochemical corrosion was established. The results showed that immersion corrosion formed a passivation film on the surface of the welded joint and formed a minimal number of pitting pits. After immersion, electrochemical corrosion testing was carried out. Due to the existence of the passivation film, the self-corrosion potential increased from-0.6 V ∼ −0.2 V–0.1 V–0.6 V, and the self-corrosion current density decreased and the fitting impedance of the film increased. These all showed that the corrosion resistance of the joint was enhanced after immersion. However, due to the combined effect of immersion corrosion and electrochemical corrosion, the potential difference between the surface passivation film and the internal metal was sufficiently large to induce pitting corrosion on the surface. After the breakdown of the passivation film, spot corrosion pits formed. Microcracks propagated along the primary β grain boundary and the α′ phase interface, and continuous corrosion for a long time may even lead to cracking failure of the welded joints. With the increase of heat input, the self-corrosion potential and the self-corrosion current density of immersion corrosion increased firstly and then decreased. The fitting film resistance value of the impedance decreased firstly and then increased. The aforementioned findings indicated that as the heat input increased, the corrosion properties of the joints firstly deteriorated and then improved.

Theoretical calculation study on the electrochemical properties of lithium halide-based artificial SEI films for lithium metal anodes

All solid-state lithium-metal batteries (ASSLMBs) have significant advantages, such as high safety and high energy density, and the solid electrolyte interface (SEI) film between the internal lithium metal anode and the solid electrolyte plays an important role. However, spontaneously formed SEI film has poor stability, leading to a decrease in the Coulombic efficiency of the cell and a shorter cycle lifetime. As a result, the research and development of artificial SEI films have become one of the hot topics in the field of lithium batteries. In this paper, the electrochemical properties of lithium halide-based artificial SEI films (LiF, LiCl, LiBr, LiI) were studied by density functional theory based on first principles. Firstly, the structural stabilities, mechanical properties, and electronic insulation of SEI films were analyzed and compared. Subsequently, the adsorption and migration behavior of lithium ions (Li⁺) on these surfaces were investigated, starting from the stable surface structures of SEI films. Based on this, the interface structures of SEI film/lithium metal were constructed by matching lattice, and their interface bonding strength and charge distribution were explored. Additionally, the inhibitory ability of SEI films on lithium dendrite growth was examined. LiF has the most stable bulk and surface structures, as well as a stable interface structure with lithium metal. Furthermore, it possesses the best mechanical properties, electronic insulation, and the ability to inhibit the growth of lithium dendrites. It can be seen that LiF is a suitable artificial SEI film for lithium metal anodes.

On the thermal impact during drilling operations in guided dental surgery: An experimental and numerical investigation

In recent years, a major development in dental implantology has been the introduction of patient-specific 3D-printed surgical guides. The utilization of dental guides offers advantages such as enhanced accuracy in locating the implant sites, greater simplicity, and reliability in performing bone drilling operations. However, it is important to note that the presence of such guides may contribute to a rise in cutting temperature, hence increasing the potential hazards of thermal injury to the patient's bone. The aim of this study is to examine the drilling temperature evolution in two distinct methods for 3D-printed surgical dental guides, one utilizing an internal metal bushing system and the other using external metal reducers. Cutting tests are done on synthetic polyurethane bone jaw models using a lab-scale automated Computer Numeric Control (CNC) machine to find out the temperature reached by different drilling techniques and compare them to traditional free cutting configurations. Thermal imaging and thermocouples, as well as the development of numerical simulations using finite element modeling, are used for the aim. The temperature of the tools' shanks experienced an average rise of 2.4 °C and 4.8 °C, but the tooltips exhibited an average increase of around 17 °C and 24 °C during traditional and guided dental surgery, respectively. This finding provides confirmation that both guided technologies have the capability to maintain temperatures below the critical limit for potential harm to bone and tissue. Numerical models were employed to validate and corroborate the findings, which exhibited identical outcomes when applied to genuine bone samples with distinct thermal characteristics.

Biomonitoring of exposure to multiple metal components in urine, hair and nails of apprentice welders performing shielded metal arc welding (SMAW)

Welding fumes are associated with various diseases. Increased air levels of metals were reported during welding. However, few multielement biomonitoring studies were conducted to assess the actual dose of metal components absorbed in apprentice welders in a learning environment. This research aimed to establish the nature and level of exposure to welding fumes and their metallic components in apprentice welders performing ‘Shielded Metal Arc Welding’ (SMAW), based on multi-element and multi-matrix analyses. A total of 86 apprentice welders were recruited in three different schools in Montreal, Québec, Canada. Twenty-one elements were measured in urine, hair, fingernail, and toenail samples collected at the beginning of the program and at the end of SMAW practical training. Concentrations of welding fumes and 12 metals were also determined in personal respirable air samples collected over a typical workday in a subgroup of 19 apprentices. Levels of manganese (Mn), iron (Fe) and nickel (Ni) in urine and Mn in hair were higher in samples taken at the end of the SMAW module compared to the beginning of training, while there was no significant difference for the other elements or for nail concentrations. Geometric mean concentrations [5th-95th percentiles] reached 0.31 [0.032–2.84], 9.4 [3.1–51] and 0.87 [0.35–3.1] μg/g creat. in post-shift urine, respectively, for Mn, Fe and Ni, and 0.37 [0.46–6.4] μg Mn/g hair at the end of SWAW. Median concentrations [5th-95th percentiles] were 29 [4.6–1200], 120 [27–3100] and 0.31 [<LOQ-0.92] μg/m3 for Mn, Fe and Ni, respectively. The work showed that even short-term welding fume exposure in controlled environments, as observed in apprentice welders after SMAW process, increases internal exposure to metals. It also confirmed the interest of measurements in multiple matrices to assess internal metal exposure. The follow-up of apprentices during standard curriculum will allow to assess more long-term internal exposure due to other welding processes.

Application of Cold Sintering Process for Stabilizing Heavy Metals in Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration fly ash (MSWI FA) consists predominantly of compounds comprising elements such as calcium, aluminum, silicon, sodium, and others. Additionally, it encompasses a complex mixture of heavy metals, chlorides, sulfates, organic pollutants, and other constituents. The effective and economically viable treatment of MSWI FA poses a formidable challenge for resource cycling at the current stage. In this research report, we adopt a novel low-temperature sintering method called the “Cold Sintering Process” (CSP) as a means to immobilize heavy metals within the fly ash. By utilizing a Taguchi orthogonal array method, we will adjust five control factors in the CSP, including sintering temperature, uniaxial pressure, sintering time, initial water addition, and sodium carbonate dosage. The leaching of cadmium from the fly ash, as measured by the Toxicity Characteristic Leaching Procedure (TCLP), will serve as the quality indicator of products. Through the application of CSP, MSWI FA was transformed into structurally stable ceramic blocks, and the heavy metals within the blocks were effectively immobilized. The results of the experiments showed that MSWI FA under the conditions of a temperature of 300 °C, uniaxial pressure of 312 MPa, sintering time in 60 min, 25 wt% water addition, and 9 wt% Na2CO3 addition could effectively reduce the leaching of cadmium by 77.71%, lead by 21.14%, zinc by 42.37%, and chromium by 99.99%, as compared to the original MSWI FA TCLP results. The X-ray Diffraction (XRD) results indicate that during the CSP, fly ash forms phases such as calcium silicate, rankinite, hydrogrossular, anorthite, and marilite. These phase transformations are considered beneficial for preventing the leaching of internal heavy metals. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) results reveal that CSP is advantageous for compacting the overall structure, and EDS results further demonstrate that some of the Pb and Zn are carried out from the interior of the blocks, with uneven distribution on the surface of fly ash particles. The aforementioned experimental results serve as preliminary indications of CSP’s capability to stabilize detrimental components within high-purity fly ash. Future research endeavors may entail the refinement of material proportions, modification of experimental parameters, and other methodologies, thus facilitating potential scalability to industrial applications. Such developments align with the overarching goal of resource utilization.

The application of hard carbon with internal quasi-lithium metal deposition in high-energy Li-ion/Li-metal hybrid batteries

The energy density of lithium-ion batteries (LIBs) with graphite as the negative electrode reaches the upper limit. The lithium ion/lithium metal hybrid batteries (HLBs) constructed by lowering the n/p of LIBs with graphite as the anodes effectively improves the energy density, but the massive plating of lithium metal (Li-M) on the surface of the graphite anode leads to rapid cell failure. In this paper, hard carbon (HC) is proposed as a better choice for anode in HLBs than that of graphite, and the difference in Li storage behaviors between HC and artificial graphite (AG) is systematically investigated. At low n/p, part of the “excess Li” is stored as quasi-lithium metal (Li-QM) in the sub-nanometer pores inside HC in a highly reversible way, which reduces Li-M plating on the surface of anodes, effectively increasing the cycle stability of HLBs. The HLBs with HC anode mass loading of 5.1 mg cm−2 and 7.8 mg cm−2 have 41.7% and 30.3% higher stack energy density compared to LIBs. Moreover, HLB-type pouch cells using HC anode with a mass loading of 7.8 mg cm−2 achieves high capacity retention of 81% after 450 cycles, while the capacity retention drops to 55% for the AG anode with the same mass loading.

Triple-electrode integrated self-supporting triboelectric nanogenerators with high output and durability based on dynamic supercritical carbon dioxide foaming

Durable and sustainable energy harvesting in harsh environments using triboelectric nanogenerators (TENGs) is a grand challenge. Herein, highly compacted and integrated TENGs are developed using dynamic supercritical carbon dioxide (scCO2) foaming technique. The self-assembled internal-electrode TENG (SAI-TENG) which is consisted of a polydimethylsiloxane (PDMS) coated internal metal electrode covered by a corrugated wrinkled foam (CWF) is readily obtained by the foaming process. The CWF can support itself and maintains air gaps to facilitate contact electrification and the biomimetic wrinkles that are induced by the scCO2 flow field, greatly enhance the triboelectric output performance. By sandwiching the SAI-TENG using two internal-electrode PDMS films, a triple-electrode integrated self-supporting TENG (TIS-TENG), which has eight-friction layers in a single device, is developed. The TIS-TENG realized maximum utilization of the wrinkled CWF surface, which is equivalent to three parallel connected TENGs. Moreover, the output was further boosted by adding tea powders and patterning micro domes on the PDMS films, which resulted in a high Voc of 106.3 V and a power density of 32.5 mW/m2. Attributing to the embedded electrode and high elasticity of CWF, the TIS-TENG has remarkable stability and tolerance to harsh conditions and can be used as self-powered sensors for monitoring vehicle parking and working conditions of workers. This work provides new insights into the green fabrication and development of highly integrated self-supporting TENGs with high performance and durability.

Methodological Foundations Protective Structures Development for Shielding Electromagnetic and Acoustic Fields

In many cases the simultaneous protection against electromagnetic and acoustic fields of wide frequency ranges is required. The complexity of such a task lies in the impossibility of significantly reducing low-frequency sound levels with traditional sound-absorbing materials, as well as the different requirements for materials that shield low-frequency and high-frequency electromagnetic fields. It is proposed to solve this problem by creating a two-layer structure, the front surface of which is solid, and the inner surface is perforated. The front panel can be made of non-conductive material. It is a variant of the Bekeshi panel and is mainly intended to reduce the level of low-frequency sound of a certain frequency with high amplitude. The perforation of the internal (metal) panel is chosen based on the need to provide shielding of electromagnetic and acoustic fields of certain frequencies or frequency bands. A calculator is provided for calculating the required panel parameters (linear dimensions, thickness, hole diameters, their number per unit of surface area). It is advisable to fill the space between the panels with a sound-absorbing material, for example, granulated polystyrene. It provides sound absorption of medium and high frequencies and makes the design broadband. The use of ferromagnetic material of the inner panel provides protection against the magnetic component of the ultra-low frequency electromagnetic field (mainly industrial). The perforation of the panel is calculated based on the waveguide theory of high-frequency electromagnetic waves. The results of tests of the effectiveness of facing metal-polymer material in the form of tiles are presented. The performance of the material is satisfactory for most industrial and domestic conditions. Determination of the mechanical properties of the material (Young's modulus, shear modulus and Poisson's ratio) showed that it is not inferior to known materials even with a large content of shielding substance. In order to rationalize the design of the structure, a priority factor and frequency (frequency band) is selected on the basis of live measurements of the electromagnetic and acoustic spectra. It is shown that the calculations have large volumes, and the solution of two-factor optimization problems is not always possible. Appropriate creation of application software to simplify the process of designing protective structures and rationalizing panel parameters based on the principles of reasonable sufficiency.

Polyploidy affects responses to Nickel in Ni-hyperaccumulating plants: Evidence from the model species Odontarrhena bertolonii (Brassicaceae)

Compared with their diploid progenitors, polyploid plants often display enhanced vigor and adaptive ability to extreme conditions. Previous studies investigated polyploid fitness under various forms of environmental stress, but whether the whole-genome duplication can affect growth, accumulation ability and tolerance levels to trace metals in metal-accumulating species remains obscure. We investigated this topic using an experimental approach and Odontarrhena bertolonii as model system. This obligate serpentine endemic includes diploid and tetraploid accessions with allopatric distribution in Tuscany and Liguria. Three diploid (2 n = 2x = 16) and three natural autotetraploid (2 n = 4x = 32) accessions were compared for growth, leaf traits, photosynthetic parameters and metal accumulation after cultivation on natural serpentine soil and in Ni-containing hydroponic solutions. In soil cultivation, shoot Ni concentration was similar in diploid and tetraploid plants, but the metal content per plant was significantly higher in polyploids because of their higher biomass production. The latter was mainly due to the production of larger leaves, coupled to a lower specific leaf area, which pointed to a better adaptation of the tetraploids to serpentine soil. In hydroponics, all the accessions showed an hormetic-like Ni effect, with stimulation of growth and photosynthesis in the low-dose zone. The data fitting to the hormetic model displayed significant differences in some parameters, with the tetraploid plants showing higher maximal length of roots and shoots and higher requirement of both external and internal Ni concentrations for optimal growth, in respect to diploid plants. On the other hand, Ni tolerance to both external and internal metal concentrations was similar in the plants of the two ploidy levels. Our results suggest that whole-genome duplication can affect the potential for growth and Ni-hyperaccumulation in obligate Ni-accumulator plants like O. bertolonii. This points to the opportunity of selecting polyploid instead of diploid accessions for environmental restoration and metal cropping practices, when the candidate species includes both chromosome races.

Analysis of Bonding Characteristics of Ag-System Brazing Filler Metal

As a filler metal for lowering the melting point of Ag, many alloy metal candidates have emerged, such as cadmium, with zinc, manganese, nickel, and titanium as active metals. However, since cadmium is known to be harmful to the human body, Cd-free filler metals are now mainly used. Still, no study has been conducted comparing the characteristics of joints prepared with and without cadmium. In addition, studies have yet to be conducted comparing the typical characteristics of brazing filler metals with special structures, and the joint characteristics of brazing filler metals with available frames. In this study, the characteristics of junctions of silver-based intercalation metals were compared based on the type of filler metal additives, using a special structure, a filler metal sandwich structure, to protect the internal base metal. The general filler metal was compared using the structure, and the thickness of the filler metal according to the thickness was reached. A comparison of the characteristics of the junction was conducted to identify the characteristics of an intersection of silver-based brazing filler metal and the effect on joint strength. Each filler metal’s collective tensile strength was measured, and the relationship between joint characteristics and tensile joint strength was explored. The junction was estimated through micro strength measurement, contact angle measurement with the base metal when the filler metal was melted, XRD image observation, composition analysis for each phase through SEM-EDS, and microstructure phase acquisition.

Linking between ambient pollution and metals concentration in blood. Nationwide study based on the national blood banking system

This study was aimed to describe the chemical traces of air pollution in blood of residents and evaluate the association between ambient pollution and its dose absorbed internally by a human body.The national Magen David Adom Blood Services blood donation collection platform and the National Public Health Laboratory's testing services were utilized to conduct a human biomonitoring study among blood donors in Israel. The donors' residential addresses and donations sites' locations were geocoded and merged with the levels of pollutants recorded by the nearby monitoring stations. Pollutants included nitrogen dioxide (NO2), sulfate dioxide (SO2), ozone (O3), carbon monoxide (CO) and particulate matter of size <10 and 2.5 μm in diameter (PM10 & PM2.5). Metal concentrations were statistically analyzed by ratio t-test and a lognormal regression, and adjusted to age, gender and smoking (defined based on Cadmium values).The findings indicate an independent positive association between pollutants and metals' concentrations in blood. Specifically, an increase in interquartile range (IQR) of NO2 was associated with 9.5 % increase in As in blood. The increase in one IQR of PM10 and SO2 was associated with an increase in Pb, of 16.6 % and 12.4 %, respectively. SO2 was also adversely associated with Cd concentrations, by increasing its levels by 5.7 %. The donors' proximity to quarries was related to the Pb blood levels higher 1.47 times compared to donors without quarries close to their residence (p-value = 0.013).To conclude, ambient pollution levels are associated with internal metals' concentrations, reaffirming the link between the two in the pathological pathway from air pollution to morbidity.

Crystallographic Characterization of Lu2O@Cs(6)‐C82 and Er2O@Cs(6)‐C82: The Role of Metal Species on Cluster Configuration†

Comprehensive SummaryIntramolecular interactions are fundamental for the unique structures and outstanding properties of metallofullerenes. However, how the internal metal species interplay with the cluster configuration inside oxide clusterfullerenes remains poorly understood. Herein, we successfully captured two oxide clusterfullerenes with different metals, namely, Lu2O@C82 and Er2O@C82, to elucidate the role of metal species in tuning cluster configuration. The two molecules have been fully characterized by mass spectrometry, Vis‐NIR absorption spectroscopy, cyclic voltammetry, and single‐crystal X‐ray diffraction. Crystallographic data show that their isomeric cages were both determined as Cs(6)‐C82. Further structural analysis reveals that the Lu1‐O‐Lu2 angle value in Lu2O@Cs(6)‐C82 is much larger than the Er1‐O‐Er2 angle value in Er2O@Cs(6)‐C82, indicating that the configuration of the endohedral oxide clusters is flexible and dependent on the metal ion radius. Additionally, electrochemical studies suggest that the variation in entrapped metal species causes differences in redox properties, for which the first oxidation and first reduction potentials of Lu2O@Cs(6)‐C82 are shifted positively and negatively, respectively, compared to the counterparts of Er2O@Cs(6)‐C82, resulting in a larger electrochemical band‐gap.

Disturbing Effect of Intra-Tissue Temperature Sensors in Pre-Clinical Experimental Studies of Radiofrequency Cardiac Ablation: A Computer-Based Modeling Study

Background: Preclinical studies on radiofrequency (RF) cardiac ablation (RFCA) use very small temperature sensors in specific positions in the tissue subjected to RF heating. Despite the sensors’ small size, the proximity to the ablation electrode and the extremely high thermal gradient around the electrode means that the presence of the temperature sensors could distort the temperatures recorded. Our objective was to assess the thermal impact of intra-tissue temperature sensors during RFCA. Methods: 3D RFCA models were built including different temperature sensors based on fiber optics and T-type thermocouples. Constant power ablation was simulated for 10 s. Results: The results showed that the disturbance caused by the presence of the T-type thermocouples was considerably greater (one order of magnitude) than that caused by the optical fibers. The closer the sensor was to the ablation electrode, the greater the greater the disturbance was and the more it increased with time in sensors more than 3 mm deep. The fiber optic measurements always slightly underestimated (&lt;0.2 °C) the tissue temperature that would exist without the sensors, while the disturbance caused by the T-type thermocouples did not always result in underestimation but depended on the depth of the sensors parallel to the catheter. Conclusions: The presence of thermocouples inserted into the tissue close to the RF ablation electrode involves a disturbance that could affect the measured temperature value, although it does not substantially alter the shape and size of the thermal lesion. Optical fibers cause much less disturbance, possibly due to the absence of internal metal parts that favor heat conduction.

Experimental Study on Catalytic Action of Intrinsic Metals in Coal Spontaneous Combustion.

In order to study the effect of inherent metals in coal on spontaneous combustion, Hongmiao lignite and Hongqingliang long-flame coal were demineralized by hydrochloric acid, the raw coal and demineralized coal were characterized by Fourier transform infrared spectrometry, X-ray diffraction, and synchronous thermal analysis experiments, and the corresponding ash content was detected by inductively coupled plasma mass spectrometry. The results show that the effect of demineralization on the volatile matter of low-rank coal is small, and the change of crystallite structure is not significant. The removed parts are mainly water-soluble salts and soluble minerals, such as carbonates and metal ions, that are not tightly bound to the organic matter of coal structure. The removed metal elements are mainly alkali metals Na and K, alkaline earth metals Ca, Mg, Sr, and Ba, and transition metals Fe, Mn, Ti, and so forth. The temperatures corresponding to the end of weight loss, ignition, and maximum weight loss rates were elevated on the thermogravimetric curves of the demineralized coal samples. The heat absorbed by evaporation of water in coal and the heat released by oxidation and combustion of coal are decreased to different degrees, indicating that the spontaneous combustion tendency of coal after demineralization is reduced, and alkali metal, alkaline earth metals, and transition metals in coal have a catalytic effect on spontaneous combustion of coal. After adding the metal chelating agent ethylenediaminetetraacetic acid (EDTA), the apparent activation energy decreased by 33.08 and 2.42%, respectively. EDTA and the alkali metal, alkaline earth metal, or transition-metal ions formed a stable chelate in coal. The catalytic activity of metals is weakened or even lost, thereby inhibiting spontaneous combustion of coal, and verifying the catalytic effect of internal metals in coal on the spontaneous combustion of coal.

Skin Cooling of Turbine Airfoils by Single Wall Effusion: Part I—Reduced Order Modeling

Abstract A quasi-1D conjugate reduced order model (ROM) is developed to capture aero-thermal physics of effusion cooling in turbine airfoils. This framework explicitly considers the coolant supply from the leading edge and its distribution to both suction and pressure sides, the internal boundary layer flow between the shell and the inner core, the hole flow, the conduction on the solid walls, as well as the external film coverage. The solid temperature is allowed to vary both in metal shell thickness and the streamwise directions. Empirical correlations are employed to model pressure loss and heat transfer in the internal sections. Compound effect of multiple effusion cooling rows are utilized to capture cooling effectiveness and the heat load. Influence of mainstream static pressure, varying blowing ratios, hole’s diameter, hole’s pitch, coolant total pressure, and total temperature distributions along streamwise direction are taken into account. In Part I, the development and validation of the model is presented, which is shown to be capable of capturing complex internal aero-thermal physics of a turbine airfoil. Film coverage capability is separately validated successfully against available flat plate experimental data, with one case including internal channel and metal conduction. In Part II of this work, effusion cooling configuration is applied over an entire micro turbine vane and an exemplary optimization is carried out in the design space to minimize coolant flow while retaining metal temperature and its gradient below some limits. It is shown in the two-part work that the developed model is suitable for parametric studies of single-wall effusion turbine cooling such that comparative accuracy is obtained at a computational time 105 times lower than computational fluid dynamics (CFD) on a whole turbine vane/blade. Together, these two papers are intended to present, validate, and optimize the ROM for skin cooling in turbine airfoils by single-wall effusion.

INTENSIFICATION OF HEAT TRANSFER IN HEAT EXCHANGE EQUIPMENT DURING CONDENSATION OF WATER VAPOR AFTER STEAM TURBINE INSTALLATIONS IN NUCLEAR POWER.

The determining parameter that characterizes the intensity of heat transfer in heat exchange equipment is the heat transfer coefficient, the value of which depends on the thermal resistances occurring in the corresponding equipment. Thus, in the heat exchanger-condenser of a steam turbine installation of a nuclear power station, this is the thermal resistance during heat transfer of cooling water in heat exchange tubes and during heat transfer of water vapor condensing in the intertube space. The value of the heat transfer coefficient also depends on the geometric and thermophysical characteristics of the heat heat exchange tubes, on the contamination of the cooling water, on the presence of air in the condensing vapors. According to the proposed scheme of the experimental setup of the "pipe in a pipe" type, calculations of the heat transfer coefficient were performed when using an external transparent glass pipe and an internal metal pipe, which was treated from the outside with a water-repellent coating that provides dropwise condensation of water vapor, as well as without treatment for film condensation. Contamination of the cooling water and the presence of air in the water vapor in both cases of condensation should be the same and as minimal as possible. The analysis of the results of the calculations allows us to draw the following conclusions: the change in the state of the outer surface of the heat exchange tubes increases the heat transfer coefficient during condensation of water vapor almost three times, which ensures an increase in the efficiency of heat transfer (more than 10%), and accordingly allows to reduce the working surface of the heat exchange equipment, which is especially relevant in modern conditions of operation of power equipment, when there is a need for emergency reconstruction of partially destroyed heat exchange equipment. Bibl. 11, Fig. 2.

STABILIZATION OF AN ANATOMICAL WAX MODEL OF THE COMPLUTENSE VETERINARY MUSEUM WITH THE HELP OF 3D DIGITAL TECHNOLOGIES

"Between the 17th and 20th centuries, polychrome beeswax anatomical models played an important role in the transmission of anatomical knowledge thanks to the high degree of accuracy and realism they were able to achieve in the representation of the most delicate structures of the organism. However, due to the fragility of this material, some of these artefacts now survive in a rather precarious state of conservation. Due to the lack of consistency of some of the internal support structures, some of these figures have been damaged or their integrity has been seriously compromised. In this article we show a case of stabilisation using a polymethylmethacrylate support of a model from the Complutense Veterinary Museum, representing the head of a horse, which has suffered the loss of some parts and shows significant cracks and fractures due to the partial collapse of the internal metal framework. The methodology used was based essentially on the use of digital technologies, to minimise the handling of the work. Based on a virtual copy obtained by 3D scanning, a specific support that fits perfectly to the surface of the figure has been designed. Subsequently, some of the pieces were produced using 3D printing in order to subject them to functional and aesthetic tests and, finally, the support was manufactured using numerical control machining. The result meets the requirements of stability and minimum aesthetic impact."