Super-high Strength Research Articles

Effect of carbon vacancy on phase formation and mechanical properties of high-entropy (Ti,Nb,Ta,Hf,W)Cx

High-entropy (Ti0.2Nb0.2Ta0.2Hf0.2W0.2)Cx with different carbon vacancies were prepared from raw binary carbides in this study. The influences of stoichiometry, particle size of raw powder, and sintering temperature on phase formation, microstructure, and mechanical properties of (Ti0.2Nb0.2Ta0.2Hf0.2W0.2)Cx were systematically investigated. The results indicate that the introduction of carbon vacancies and using finer raw binary carbide powders can both significantly enhance the formation ability of single-phase composition with uniform elemental distributions. The formation of a high-entropy phase could enhance the Vicker’s hardness. The flexural strength is greatly influenced by the content of carbon vacancy, which is greatly detrimental to flexural strength. The fracture toughness is determined by both the content of carbon vacancies and the presence of secondary phases. By optimizing the content of carbon vacancies, particle size of raw powders, and sintering temperature, (Ti0.2Nb0.2Ta0.2Hf0.2W0.2)C shows super high flexural strength of 743 MPa and fracture toughness of 8.6 MPa m-1/2.

Super high strength of annealed Fe32Cr33Ni29Al3Ti3 manufactured by selective laser melting

Selective laser melting (SLM) of high entropy alloys (HEAs) shows great potential in industry applications and annealing was always used as a post-processing method after SLM. A dual-phase (DP) Co-free HEA was manufactured by SLM and annealed at 900 °C in this work. The annealed HEA exhibited super high yield and tensile strengths (∼1224 and ∼1363 MPa, respectively), higher than those of the as-printed sample, primarily attributed to grain refinement and spinodal decomposition with FCC phase (rich in Ni/Al/Ti) and BCC phase (rich in Cr/Fe) decomposing into FCC (rich in Fe), B2 (rich in Cr, poor in Ni), and L12 (rich in Ni/Al/Ti, poor in Fe/Cr) during annealing. The annealed DP Co-free HEA exhibits notably superior strength to other Co-free HEAs or medium entropy alloys (MEAs) produced via SLM. Due to their affordability, Co-free HEAs show immense potential for widespread commercial use, and this study explores annealing in SLM to improve the mechanical properties of HEAs. The high-strength annealed DP Co-free HEA could be especially valuable for structural elements in construction applications.

Significantly improved strength of the TiC/TA19 composites via interface and dislocation strengthening

For titanium matrix composites (TMCs) with a dual-phase structure, yield strength (YS) is typically governed by the hard α phase rather than the soft β phase in the matrix alloy. Therefore, by controlling the precipitation of nanoscale secondary α phases (αs) within the β phase, lattice distortion can be induced, leading to dislocation pile-ups at the αs/β phase interface, thereby achieving strengthening of the matrix interface. Herein, TiC/TA19 composites were fabricated using spark plasma sintering, and induced the dispersion and pinning of nanoscale αs phases from the β phase at the αs/β phase interface through multi-pass cumulative rolling, achieving super high strength. In particular, the nanoscale αs phase exhibits two typical Burgers orientation relationships with the β phase, i.e. (0001)αs//(110)β & [11 2− 0]αs//[1− 11]β and (0001)αs//(01 1−)β & [11 2− 0]αs//[1− 11]β, respectively. Compared with the yield strength of sintered composites, when the rolling reduction was 75 %, the YS of TiC/TA19 composites increased by 33.7 %, reaching 1368 MPa, and the elongation was 3.6 %, only 0.7 % lower than that of sintered composites (4.3 %). The enhanced strength is mainly attributed to the αs precipitation for αs/β interface strengthening and dislocation strengthening derived from the TiC and nanoscale αs precipitates. The volume fraction of dynamic recrystallization grains in TiC/TA19 composites increased with the rolling reduction, and more pyramidal <c+a> slip systems were activated to coordinate the plastic deformation of the composites. This study offers a promising route to fabricating superior high-strength TMCs and provides new insights into balancing strength and ductility.

Formation of dual quasi-continuous networked structure and its strengthening effect in Ti-6Al-4V alloy reinforced with graphene via powder bed fusion

A dual-networked distribution of the reinforcements holds promise for achieving a balance between high-strength and moderate plasticity in titanium matrix composites (TMCs). Unfortunately, achieving this improvement in TMCs via additive manufacturing (AM) methods, presents significant challenges. Those challenges arise from the inherent differences in chemical and physical properties, which often led to agglomeration of the reinforcement and cracks caused by the high thermal residual stresses. To overcome those issues, this study focuses on the development of Ti-6Al-4V (Ti64) alloys incorporated with 0.5 wt% graphene nanosheets (GNSs) constructing a dual quasi-continued TiC network structure via powder bed fusion. The results exhibited a super-high tensile yield strength (1307 MPa), accompanied by a moderated elongation of 2.6% with reduced residual stress. The microstructure, phase contents, and mechanical performance were thoroughly investigated. A thermo-metallurgical-mechanical coupling model was developed, considering factors such as laser absorption effects and laser scanning strategy. Finally, a reasonable dual-network model was built to elucidate the contribution of various strengthening factors. Overall, this study illustrates that the strength of GNS/Ti64 composites is affected by the factors of GNS distribution, quasi-continue network in-situ TiC particles, temperature and residual stress field, offering a reference for fabricating high-strength nanocarbon/Ti64 composites by AM methods.

A super hydrophilic and high strength chitosan hemostatic sponge prepared by freeze-drying and alkali treatment for rapid hemostasis

Excessive blood loss caused by natural accidents or major surgical procedures can be life-threatening and requires rapid hemorrhage management. Developing hemostatic materials with high water absorption capacity and high strength properties is still challenging. Super hydrophilic/high-strength chitosan hemostatic sponges (SHHS-CHS) were prepared by freeze-drying and alkali treatment. The freeze-drying technology formed a porous three-dimensional structure of sponges, and alkali treatment increased the hydrophilicity of sponges and the rigidity of the chitosan molecular chain, improving the hydrophilicity and mechanical properties of chitosan sponges. Characterization experiments revealed that SHHS-CHS had high water absorption capacity, rich pore structure, and excellent mechanical properties. The cytotoxicity and hemolysis experiments showed that SHHS-CHS had good biocompatibility. Compared to the commercial hemostatic gelatin sponges and chitosan hemostatic material, SHHS-CHS had better blood coagulation and red blood cell and platelet adhesion ability. Moreover, SHHS-CHS showed better hemostatic ability than gelatin sponges in rat-liver injury and rat leg vein rupture models, significantly reducing the hemostasis time and bleeding volume. In conclusion, SHHS-CHS has broad prospects for clinical application as a hemostatic material.

Nontoxic, precious-metal-free titanium-based metallic glasses with exceptional glass-forming ability and high specific strength

Titanium-based metallic glasses (TBMGs) are attracting broad interest due to their simultaneous light weight, superhigh strength, and specific strength, exceptional wear- and corrosion-resistance and biocompatibility, desirable for electronic, biomedical, and aerospace applications. However, the glass-forming ability (GFA) of TBMGs, except some containing significant amount of toxic (Be) or precious (Pd, Ag) elements, is disappointingly low, as manifested by a critical casting diameter (dc) not more than 6 mm, which significantly restricts their manufacturing and applications. Here, we report our discovery of a series of TBMGs in the (TiZrHf)x(CuNi)y(SnSi)z pseudo-ternary system. These alloys possess an exceptionally large dc, reaching up to 12 mm, doubling the current record for Be and precious-metal free TBMGs. Moreover, these alloys exhibit a low density (7.0–7.3 g/cm3), high fracture-strength (up to ∼2700 MPa), high specific fracture-strength (up to ∼370 N m g−1), and even good plasticity with a plastic strain of up to 9.4% upon compression. They also possess high activation energy for crystallization and high atomic packing efficiency, which provide an initial physical account for their exceptional GFA and manufacturability.

Achieving low tension-compression yield asymmetry and ultrahigh strength in Mg–1Al–1Ca–0.2Mn (wt%) alloy via sub-micron grain refinement

Traditional low-alloyed Mg–Al–Ca–Mn extrusion alloys always show a low strength and a high tension-compression yield asymmetry. In the present work, Mg–1Al–1Ca–0.2Mn (AXM1102, wt.%) alloys were extruded at 150–350 °C to produce different grain structure and mechanical properties. It is shown that AXM1102-150 (extruded at 150 °C) sample exhibits superhigh strength in both tension and compression, which exhibited a yield strength (YS) of 428 MPa in tension and 416 MPa in compression. Namely, ultrahigh strength and low tension-compression yield asymmetry were both obtained. The ultrahigh strength was found to be ascribed to the ultra-fine dynamically recrystallized (DRXed) grains (0.47 μm) together with grain boundary co-segregation of Ca and Al atoms. Submicron DRXed grains accounts for the improved tension-compression yield asymmetry through suppressing {10-12} twining during compression. Additionally, the discontinuous yielding was detected during tension of AXM1102-150 alloy, which is potentially related with the high energy barrier required for dislocation emission caused by grain boundary co-segregation of Al and Ca atoms. Once the tensile stress reaches the peak value, the mobile dislocation density increases immediately, thus the tensile stress-strain behavior of the AXM1102-150 alloy is dominated by strain softening. The results indicate that low-alloyed Mg–Al–Ca–Mn alloys demonstrate tremendous potential as next generation ultrahigh-strength and low tension-compression yield asymmetry wrought Mg alloys.

Microstructure Characterization and Mechanical Properties of Laser Welded Super High Strength QP980 Automotive Steel

The Ultrahigh strength Q&amp;P automotive steel, i.e. QP980, has a broad application prospect in lightweight due to its high strength and good plasticity. In this study, the range of heat input (30 ~ 40 J/mm) was selected by controlling laser power in laser welding of QP980 in order to investigate the microstructure and properties of welded joint. At the heat input of 30 ~ 40 J/mm, the joint of QP980 had acceptable penetration. The weld widths were 417.93 mm, 582.02 mm and 521.56 mm, respectively. The macroscopic morphology of the joint is hourglass type. The microhardness of the welded joint hardening zone is higher than that of the base metal, and the maximum value is 519 HV0.5. When the heat input is 35 J/mm, the tensile strength of the welded joint is 1109 MPa. The maximum joint factor is 91.88 %. The fracture is close to the base metal. A large number of dimples are observed on the fracture surface, implying as ductile fracture. Based on the EBSD results, the proportion of low angle grain boundary was consistent with mechanical properties. A large number of deformation twins are formed in the 35 J/mm sample through deformation, which has a great contribution to the strength of the weld.

Nano-precipitation strengthening regulated by nanotwins in CoCrNi alloy with super-high strength

The number and size of precipitates directly influence the strengthening of the high-temperature alloys. As special coherent interfaces, nano-twinned (NT) boundaries are pre-set in CoCrNi-based superalloy to regulate the distribution of nano-precipitates for further strengthening the mechanical property. High density of NTs with twin spacings of 2–200 nm is produced in CoCrNi alloy by surface mechanical rolling treatment (SMRT), and L12 (Ni3Ti)-type precipitates are induced by the low-energy NT boundaries, as well as grain boundaries, after aging at 700 °C for 4 h. The CoCrNi alloy with L12 nano-precipitates exhibits a super-high mechanical property, characterized by 2019 MPa of a yield strength (σy) and 2300 MPa of an ultimate tensile strength (σu), much higher than the CoCrNi alloy counterpart of 840 (σy) and 1100 (σu) MPa, respectively. Meanwhile, the treated CoCrNi alloy also delivers a reasonable elongation of 7.0%. The super-high strength is mainly ascribed to the high density L12 nanoprecipitates grown on the NT boundaries, while the elongation is sustained by the NTs boundaries.

Remarkable cryogenic properties by deformation twinning in a coherent precipitation-containing high entropy alloy

Developing structural alloys for critical cryogenic applications is a challenging yet essential task, primarily due to the ductile-brittle transition phenomenon. To address this issue, we developed a twinning-aided coherent precipitation-containing Co45Cr15Ni30Al5Ti5 high entropy alloy (HEA) with remarkable cryogenic properties. The activation threshold for twinning was successfully reduced via the disordering behavior of the L12 phase. In the present work, distinct temperature-dependent deformation behavior was observed. The dominant room-temperature strain accommodation mechanism was found to be the dislocation slip coupled with architectured stacking faults (SFs) and immobile Lomer-Cottrell (L-C) locks. Whereas, deformation twins were readily formed under cryogenic tensile loading, leading to significantly increased yield strength and ultimate tensile strength, approaching 1.5 GPa and 1.9 GPa, respectively. The remarkable cryogenic work hardening behavior contributes to persistent elongation of up to 31 % and the super-high ultimate tensile strength. The presence of SFs, deformation twins, and their interactions provide significant strain-hardening capability.

Impact of Aging Treatment on Microstructure and Performance of Al-Zn-Mg-Cu Alloy Thin Sheets

Al-Zn-Mg-Cu alloy, recognized for its heat-treatable and super-high strength, is a pivotal material for critical structural components in aviation. Consequently, grasping the intricate relationship between heat treatment processes and the microstructural characteristics and properties of the Al-Zn-Mg-Cu alloy is of paramount practical significance. This study encompasses a spectrum of heat treatment methodologies, delving into the diverse effects of distinct aging treatments on the microstructure and performance of thin Al-Zn-Mg-Cu alloy sheets. The findings illuminate that short natural aging treatments bestow heightened strength and hardness upon the alloy, albeit at the expense of ductility. Nevertheless, the alloy retains commendable malleability, enabling significant cold deformation. In contrast, artificial aging markedly elevates the alloy’s strength and hardness, albeit concurrently inducing a precipitous decline in ductility, thereby attenuating the alloy’s cold formability.

Superhydrophobic coating with super-high adhesive strength to substrate

Porous and hydrophilic concrete coating on the insulation layers of dam suffered from adhesion of cold water and subsequent icing in a freezing environment, which might result in severe ice pullout phenomenon. Although a lot of superhydrophobic concrete (SC) coatings have been developed, the coatings generally had poor adhesive strength with the insulation layers, which restricted their application in protecting the insulation layers. Herein, we first developed a novel superhydrophobic polymer concrete (SPC) coating by polyacrylate emulsion (PAE) and stone protector addition, and nylon mesh cover. The SPC coating exhibited good superhydrophobicity with a contact angle of ∼156° and a sliding angle of ∼10°. And the adhesive strength between SPC coating and insulation layer was 96 % larger than that of SC coating, indicating much better performance in the insulation layer protection. In addition, the SPC coating possessed excellent surface robustness, anti-icing capacity, and self-cleaning property, and was expected to be a promising candidate for protecting the insulation layers.

Formation mechanism of ultrafine α lamellae with high-density dislocations in Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy fabricated by laser powder bed fusion

This study employed laser powder bed fusion (LPBF) to fabricate Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) alloy, and the microstructural characteristics and mechanism of α phase formation were investigated. Results revealed that the as-deposited sample, after undergoing stress relief annealing, exhibited a microstructure characterized by a high volume fraction of ultrafine nanoscale α phases dispersed throughout. Abundant edge dislocations and dislocation loops were observed within the α phase, while dislocations were scarcely detected in the β phase. The formation of ultrafine nanoscale α phases occurs during the subsequent low-temperature stress relief annealing process following additive manufacturing. After stress relieving, the Ti17 sample exhibited a superhigh tensile strength of nearly 1500 MPa.

Rationally designed anode and gel polymer electrolyte for high-performance zinc-ion hybrid supercapacitors

Aqueous zinc ion hybrid supercapacitor (ZIHS) remains a challenge to achieve the practical usage of ZIHS with long service life due to the Zn dendrite growth and side reactions. Herein, a combined strategy is proposed to effectively improve the electrochemical performance of ZIHS devices. It consists of three approaches to engineer gel polymer electrolyte (GPE), protective layer for Zn anode, and redox reaction of catholyte, respectively. The optimal GPE demonstrates a super-high strength of 3.22 MPa and a satisfactory ionic conductivity of 70.9 mS cm−1. The optimal Zn anode coated with a protective layer of sulfonated polyether ether ketone and vermiculite exhibits highly reversible Zn plating/stripping behavior over 1000 h in the symmetric cell with an optimal GPE. The introduction of ZnBr2 with an optimal content can result in a 90% energy density increase at least through Br‾/Br3‾ redox reactions. The resultant ZIHS delivers an energy density of 68.59 Wh kg−1 at a power density of 1677.5 W kg−1, and ultra-long cycling stability with ∼88% capacitance retention after 40,000 cycles at 5 A g−1. It is believed that this strategy could provide a meaningful guide for the design and construction of high-performance ZIHS devices.

Reaction mechanism and microstructure evolution of superhigh strength in-situ TiC/Ti composite based on Cr2AlC-Ti system

In the field of exploring the precursors of TiC/Ti composite, Cr2AlC was innovatively used as the precursor in this study. Based on the formation of TiC in pure Ti matrix during hot-pressing sintering, Al and Cr elements changed the microstructure of matrix to form TiC/(α + β)-Ti composite, and the reaction mechanism of Cr2AlC-Ti system in the sintering process was discussed in detail. During the cooling process, Cr element retained β-Ti to room temperature, and the uniformly distributed TiC was used as the nucleation site of α-Ti. By controlling the content of Cr2AlC added, the microstructure of the composite was regulated. In 10 vol% Cr2AlC/Ti composite, the α-Ti extend form the boundary of TiC to all sides, forming a microstructure of quasi-continuous network structure covering equiaxed β-Ti, which exhibited the optimal strength with ultimate tensile strength of 1184 MPa. The interface analysis shown that there is good interface bonding at TiC/α-Ti, which made the whole frame have good load transfer. And there were stacking faults at the TiC/β-Ti interface, meaning the obvious CTE mismatch strengthening at it.

Tribological Mechanism of Graphene and Ionic Liquid Mixed Fluid on Grinding Interface under Nanofluid Minimum Quantity Lubrication

Graphene has superhigh thermal conductivity up to 5000 W/(m·K), extremely thin thickness, superhigh mechanical strength and nano-lamellar structure with low interlayer shear strength, making it possess great potential in minimum quantity lubrication (MQL) grinding. Meanwhile, ionic liquids (ILs) have higher thermal conductivity and better thermal stability than vegetable oils, which are frequently used as MQL grinding fluids. And ILs have extremely low vapor pressure, thereby avoiding film boiling in grinding. These excellent properties make ILs also have immense potential in MQL grinding. However, the grinding performance of graphene and ionic liquid mixed fluid under nanofluid minimum quantity lubrication (NMQL), and its tribological mechanism on abrasive grain/workpiece grinding interface, are still unclear. This research firstly evaluates the grinding performance of graphene and ionic liquid mixed nanofluids (graphene/IL nanofluids) under NMQL experimentally. The evaluation shows that graphene/IL nanofluids can further strengthen both the cooling and lubricating performances compared with MQL grinding using ILs only. The specific grinding energy and grinding force ratio can be reduced by over 40% at grinding depth of 10 μm. Workpiece machined surface roughness can be decreased by over 10%, and grinding temperature can be lowered over 50 ℃ at grinding depth of 30 μm. Aiming at the unclear tribological mechanism of graphene/IL nanofluids, molecular dynamics simulations for abrasive grain/workpiece grinding interface are performed to explore the formation mechanism of physical adsorption film. The simulations show that the grinding interface is in a boundary lubrication state. IL molecules absorb in groove-like fractures on grain wear flat face to form boundary lubrication film, and graphene nanosheets can enter into the grinding interface to further decrease the contact area between abrasive grain and workpiece. Compared with MQL grinding, the average tangential grinding force of graphene/IL nanofluids can decrease up to 10.8%. The interlayer shear effect and low interlayer shear strength of graphene nanosheets are the principal causes of enhanced lubricating performance on the grinding interface. EDS and XPS analyses are further carried out to explore the formation mechanism of chemical reaction film. The analyses show that IL base fluid happens chemical reactions with workpiece material, producing FeF2, CrF3, and BN. The fresh machined surface of workpiece is oxidized by air, producing NiO, Cr2O3 and Fe2O3. The chemical reaction film is constituted by fluorides, nitrides and oxides together. The combined action of physical adsorption film and chemical reaction film make graphene/IL nanofluids obtain excellent grinding performance.

An ultra-high-strength 12Mn maraging steel realized via nanoscale heterostructure engineering

A 12Mn maraging steel Fe-12Mn-5Co-1Ti-1Mo-1Si, strengthened by the Heusler Fe2TiSi phase, was designed with nanoscale heterostructures. When aged at 450 °C, fine Fe2TiSi particles uniformly precipitate within the martensite lath, contributing as the main strengthening phase. At the same time, a nanoscale austenite layer was observed to grow at the lath interface, significantly toughening the martensite lath matrix. With this hierarchical nano-structure, the super-high tensile strength of ∼1700 MPa with good elongation of ∼7 % at break was achieved. Our case uncovers that hierarchical nanoscale heterogeneous microstructure could pave a new path to achieve synergistic improvement of strength and ductility..

Achieving ultrahigh specific strength of an ultrafine grained Mg–9Li–1Al alloy via the combined processing of ECAP with repeated annealing and rolling

A super-high strength Mg–9Li–1Al (LA91) alloy with ultimate tensile strength (UTS) of 312 MPa and specific strength of ∼215 kNmkg−1 was successfully achieved via a combined processing of multi-pass equal-channel angular pressing (ECAP) with repeated annealing and room temperature (RT) rolling. Significant grain refinement after ECAP led to the formation of ultrafine-grain (UFG) α-Mg phase with grain size of ∼350 nm. Further refinement of the α-Mg grains reaching ∼200 nm was achieved by further repeated annealing and RT-rolling with high dislocation density. The formation of strong basal texture of the α-Mg phase of the combined-processed alloy also contributed to the achieved excellent strength-ductility synergy. The 1 wt% Al (aluminum) in the Mg–Li dual-phase matrix acted as a high-efficient strengthening element, and was the major contributory factor to the 48% improved specific strength of the alloy compared to the UFG Mg–9Li binary alloy in our former study. The Al element distributing throughout the alloy phases without segregation contributed to the enhanced refinement of the α-Mg grains during the combined processing and improved strain-hardening rate during the tension plastic deformation, allowing for the achievement of a high strength of the LA91 alloy.

Frequency domain full waveform inversion with small‐scale laboratory measurements for reconnaissance in mechanized tunneling

AbstractIn mechanized tunneling, so‐called tunnel boring machines (TBMs) drill through the ground in an automatized manner. Therefore, the drilling process is very efficient but the maintenance costs are high. Seismic exploration seems appropriate to identify changing ground conditions in front of the TBM to reduce costs from damages of the TBM and from the corresponding dwell times. Today's seismic exploration techniques are using only a small amount of the information, which is contained in the seismic records from field observations, whereas full waveform inversion (FWI) tries to use the whole content. The potential of different FWI approaches for the application in mechanized tunneling has been investigated. An analysis of the performance of FWI not only employing synthetic examples but additionally measured waveforms is essential. Since seismic surveys at the construction side are not performed with FWI in mind, the data sets are usually not appropriate for testing the developed algorithms. Nevertheless, a validation of FWI approaches by measured waveforms is possible by using waveform recordings from a small‐scale experimental setup. A small‐scale super high strength grout specimen is constructed for validating an adjoint frequency domain FWI approach. Frequency domain models compute the seismic response of a system for an infinite time interval. The attenuation of the material as well as the attenuation effects at the free surfaces are hard to quantify over an infinite time interval. Therefore, the specimen is designed in a way that four of the six borders can be modeled as absorbing boundaries. For this purpose, the displacement recordings are truncated just before the waves that are reflected at the excluded borders arrive at the measurement points. This design in combination with a notch representing a rectangular tunnel makes the measurements more similar to data from a tunnel construction side. A rectangular hole is embedded in the specimen and acts as material discontinuity, which the FWI approach is aiming to detect.

Network Structure and Water Absorption of Soil Moisture Gel by Coarse-Grained Molecular Dynamics Simulations

With the wide application of hydrogel materials in agriculture, forestry, flexible electronics, electronic information engineering, environmental detection, flexible electronics, information science, technology and so on, the development of various new functional hydrogel materials has gradually become one of the research hotspots. At present, the research on hydrogel materials is mainly focused on the preparation of various functional hydrogels by experimental methods, there is no fundamental understanding of the relationship between the “stimulus-response” and its inner microstructures. In this paper, the author uses the molecular dynamics simulation method to study the evolution of the hydrogel’s microscopic network structure, the relationship between microstructure and water absorption of hydrogels in the processes of water swelling and “stimulus-response”. The next generation of new super absorbent, high toughness, high strength and other functional hydrogels could be synthesized by the guide of this study, and these new hydrogels have a promising future to apply in new fields of technology such as flexible electronics, and biological medicine.