Application of frequency characteristic extraction in increasing the accuracy of X-ray based thickness gauges used for aluminum alloys employing GMDH neural network

Radiation-based gauges have been widely utilized in the industry as a dependable, non-destructive method of measuring metal layer thickness. It is only possible to trust the conventional radiation thickness meter when the material's composition is known in advance. Thickness measurement errors are to be anticipated in contexts like rolled metal factories, where the real component of the material could diverge greatly from the stated composition. An X-ray-based device was suggested in this study to measure aluminum sheet thickness and identify the type of its alloys. Transmission and backscattered X-ray energy were recorded using two sodium iodide detectors while a 150 kV X-ray tube in the described detection system was operated. Aluminum layers of varying thicknesses (2-45 mm) and alloys (1050, 3105, 5052, and 6061) were simulated to be placed between the X-ray source and the transmission detector. The development of radiation-based systems used the MCNP code as a very powerful framework to imitate the detecting architecture and the spectra acquired by the detectors. The recorded signals were transferred to the frequency domain using the Fourier transform, and the frequency characteristics were extracted from them. Two GMDH neural networks were trained using these characteristics: one to identify the alloy type and another to determine the aluminum layer's thickness. The classifier network had a 92.2% success rate in identifying the alloy type, while the predictive network had a 1.9% error rate in determining the thickness of the aluminum layer. By extracting important characteristics and using powerful neural networks, this study was able to improve the precision with which aluminum layer thickness was measured and correctly identify the alloy type. The suggested method is used to determine the thickness of aluminum and its alloy sheets and may also be applied to other metals.

Hollow-Structured N-doped carbon-embedded CoFe NanoAlloy for boosting activation of Monopersulfate: Engineered interface and heteroatom Doping-Induced enhancements

While transition metals are useful for activating monopersulfate (MPS) to degrade contaminants, bimetallic alloys exhibit stronger catalytic activities owing to several favorable effects. Therefore, even though Co is an efficient metal for MPS activation, CoFe alloys are even more promising heterogeneous catalysts for MPS activation. Immobilization/embedment of CoFe alloy nanoparticles (NPs) onto hetero-atom-doped carbon matrices appears as a practical strategy for evenly dispersing CoFe NPs and enhancing catalytic activities via interfacial synergies between CoFe and carbon. Herein, N-doped carbon-embedded CoFe alloy (NCCF) is fabricated here to exhibit a unique hollow-engineered nanostructure and the composition of CoFe alloy by using Co-ZIF as a precursor after the facile etching and Fe doping. The Fe dopant embeds CoFe alloy NPs into the hollow-structured N-doped carbon substrate, enabling NCCF to possess the higher mesoscale porosity, active N species as well as more superior electrochemical properties than its analogue without Fe dopants, carbon matrix-supported cobalt (NCCo). Thus, NCCF exhibits a considerably larger activity than NCCo and the benchmark catalyst, Co3O4 NP, for MPS activation to degrade an environmental hormone, dihydroxydiphenyl ketone (DHPK). Besides, NCCF + MPS shows an even lower activation energy for DHPK degradation than literatures, and retains its high efficiency for eliminating DHPK in different water media. DHPK degradation pathway and ecotoxicity assessment are unraveled based on the insights from the computational chemistry, demonstrating that DHPK degradation by NCCF + MPS did not result in the formation of toxic and highly toxic by-products. These features make NCCF a promising heterogeneous catalyst for MPS activation to degrade DHPK.

NiFeRu/C and Ru, Fe-Ni5P4/C as complementary electrocatalyst for highly efficient overall water splitting

Designing and fabricating highly competent and inexpensive electrocatalysts are highly desirable for application in electrocatalytic water splitting. In this study, we synthesized NiFeRu/C nanofibers and Ru, Fe dual-doped Ni5P4 (Ru, Fe-Ni5P4)/C nanofibers as complementary electrocatalysts for overall water splitting through electrospinning, carbonization, and phosphorization treatment, respectively. The NiFeRu/C nanofibers and Ru, Fe-Ni5P4/C nanofibers showed high hydrogen evolution reaction and oxygen evolution reaction activity, respectively, due to the presence of numerous exposed active sites and optimized adsorption capacity for the reaction intermediates contributed by the synergistic interaction among different metal components in the electrocatalysts. Hence, the assembled asymmetrical electrolytic cell effectively promoted overall water splitting, requiring a voltage of 1.569, 1.744, and 1.872 V to achieve a current density of 100, 500, and 1,000 mA cm-2, respectively, and it was better than Pt/C||IrO2. Additionally, the electrolytic cell could work at 500 mA cm-2 for 100 h without any noticeable deterioration in activity, which indicated that it was durable at high current density. In this study, we described a novel method for designing highly efficient electrocatalysts for overall water splitting.

Anchoring cobalt molybdenum nickel alloy nanoparticles on molybdenum dioxide nanosheets as efficient and stable self-supported catalyst for overall water splitting at high current density

Developing bifunctional electrocatalysts with efficient and stable catalytic performance at high current density to improve the productivity of water splitting is important for relieving the environmental pollution and energy crisis. Herein, the Ni₄Mo and Co₃Mo alloy nanoparticles were anchored on MoO₂ nanosheets (H-NMO/CMO/CF-450) by annealing the NiMoO₄/CoMoO₄/CF (CF: self-made cobalt foam) under Ar/H₂ atmosphere. Benefitting from the nanosheets structure, synergistic effect of the alloys, existence of oxygen vacancy and the cobalt foam with smaller pore sizes as conductive substrate, the self-supported H-NMO/CMO/CF-450 catalyst demonstrates outstanding electrocatalytic performance, which delivers small overpotential of 87 (270) mV at 100 (1000) mA·cm^-2 for HER and 281 (336) mV at 100 (500) mA·cm^-2 for OER in 1 M KOH. Meanwhile, the H-NMO/CMO/CF-450 catalyst is used as working electrodes for overall water splitting, which just require 1.46 V @ 10 mA·cm^-2 and 1.71 V @ 100 mA·cm^-2, respectively. More importantly, the H-NMO/CMO/CF-450 catalyst can stabilize for 300 h at 100 mA·cm^-2 in both HER and OER. This research provides an idea for the preparation of stable and efficient catalysts at high current density.

Reducing industrial noise by the use of damping alloys when manufacturing mining equipment parts

The existing experience of noise and vibration specialists has shown that the problem of noise reduction is very relevant, especially for the mining industry. Traditional methods of dealing with industrial noise are not effective enough. In solving this issue, it is advisable to reduce the noise level at the source of its occurrence through the use of metal alloys with enhanced dissipative properties. The article presents the results of experimental studies of developing steels with increased damping properties for manufacturing perforator parts: bit bodies and drill rods. In this article, the sound pressure level of alloys dependence on the type of heat treatment has been studied, and the optimal content of alloying elements has been established to ensure the development of the ferrite-pearlite structure. This structure is characterized by an increased dislocation density and is the reason for reducing the noise of the drill rod and the body of the perforator bit by 10-12 dB A. In addition, the article establishes the pattern of noise intensity at different frequency intervals for standard and developed alloys.

Effect of exfoliation corrosion on the efficient hybrid joint of AA2024-T3 and AA2198-T8 formed by friction stir welding

The third-generation alloy, AA2198-T8, is highly recommended for the aerospace industry. However, it has come under scrutiny due to its high cost. This study aims to decrease the cost of manufacturing through a hybrid design that uses AA2198-T8 alloys for the crucial parts and AA2024-T3 alloys for the remaining structure. The two main techniques for joining AA2024-T3 to AA2198-T8 are reversed double-sided friction stir welding (DS-FSW) and traditional single-sided friction welding (SS-FSW). They were carried out under unaltered tool rotation speed followed by five different welding speeds. The mechanical properties of the joints were explored, and the maximum joining efficiency of the welding process was 96% for reversed DS-FSW at 102 mm/min welding speed. The hybrid joint was tested for compliance with ASTM G34 standards to examine the welding joint's exfoliation corrosion (EXCO) for eight exposure times. The findings showed that joint efficiency decreased relative to as-welded joints, and mechanical property deterioration increased with EXCO exposure duration, reaching 40% for specimens exposed for 120 h to the corroding solution. It has been noted that morphology and grain size changes significantly impact EXCO.

Ternary alloy (FeCoNi) nanoparticles supported on hollow porous carbon with defects for enhanced oxygen evolution reaction

Low-cost non-noble metal nanoparticles are promising electrocatalysts that can catalyze oxygen evolution reaction (OER). Various factors such as poor activity and stability hinder the practical applications of these materials. The electroactivity and durability of the electrocatalysts can be improved by optimizing the morphology and composition of the materials. Herein, we report the successful synthesis of hollow porous carbon (HPC) catalysts loaded with ternary alloy (FeCoNi) nanoparticles (HPC-FeCoNi) for efficient OER. HPC is firstly synthesized by a facile carbon deposition method using the hierarchical porous zeolite ZSM-5 as the hard template. Numerous defects are generated on the carbon shell during the removal of zeolite template. Subsequently, FeCoNi alloy nanoparticles are supported on HPC by a sequence of impregnation and H₂ reduction processes. The synergistic effect between carbon defects and FeCoNi alloy nanoparticles endows the catalyst with an excellent OER performance (low overpotential of 219 mV; Tafel slope of 60.1 mV dec^-1) in a solution of KOH (1 M). A stable potential is maintained during the continuous operation over 72 h. The designed HPC-FeCoNi presents a platform for the development of electrocatalysts that can be potentially applied for industrial OER.

Pd-Based Metallenes for Fuel Cell Reactions

Pd-based metallenes, atomically thin layers composed primarily of under-coordinated Pd atoms, have emerged as the newest members in the family of two-dimensional (2D) nanomaterials. Moreover, the unique physiochemical properties, high intrinsic activity associated with metallenes coupled with the ease of applying chemical modifications result in great potential in catalyst engineering for fuel cell reactions. Especially in recent years, interest in Pd-based metallenes is growing, as evidenced by surge in available literatures. Herein, we have reviewed the recent findings achieved in Pd-based metallenes in fuel cells by highlighting the technologies available for deriving metallenes and manifesting the modification strategies for designing them to better suit the application demand. Moreover, we also discuss the perspective insights of Pd-based metallenes for fuel cells regarding the surfactant-free synthesis method, strain engineering, constructing high-entropy alloy, and so on.

Numerical Simulation of Surface Plasmon Resonance Optical Fiber Biosensor Enhanced by Using Alloys for Medical Application

Tuberculosis is a very dangerous disease. Therefore, early and quick diagnosis of this disease can increase the chances of overcoming it. Studies show that people with tuberculosis have a lower blood plasma refractive index than healthy people. The performance of the fiber optic sensor based on surface plasmon resonance is investigated for the metal/oxide/graphene structure and for cases where the diameter of the fiber optic core is 300, 600, and 940 µm while blood plasma is considered as the sensing medium. The sensor characteristics such as sensitivity, detection accuracy and figure of merit are simulated for each structure using the theory of matrix method in Wolfram Mathematica software. The simulation results show that the aluminum/lutetium oxide/graphene structure has the highest quality factor when the core diameter of the optical fiber is 940 µm. In continuation of this research, the effects of using alloys with different mixture proportions to improve the quality are investigated. According to results, the structure of aluminum/copper alloy (with a ratio of 30/70)-lutetium oxide graphene is the best choice for improving the quality of the sensor.

Hydrogen evolution reaction catalysis on RuM (M = Ni, Co) porous nanorods by cation etching

The development of efficient and stable nanomaterial electrocatalysts for the hydrogen evolution reaction (HER) is of great significance for renewable energy conversion via water electrolysis. Herein, we have developed a novel class of bimetallic RuM (M = Ni, Co) hollow nanorods (HNRs) through a facile Fe³⁺ etching strategy, as electrocatalysts for enhancing the HER. Morphological physical characterization and electrochemical tests demonstrated that RuM (M = Ni, Co) HNRs with hollow structures can effectively enhance electrocatalytic activity due to their high specific surface areas. Impressively, the RuNi HNRs exhibited superior HER performance with an overpotential of merely 25.6 mV in 1 M KOH solution at 10 mA cm^-2, which is significantly lower than that of commercial Pt/C (44.7 mV). Moreover, the as prepared RuNi HNRs showed excellent stability and could continuously work at a current density of 10 mA cm^-2 for 40 h with a negligible increase in potential. The Ru-based HNRs also showed high HER activity in an acidic solution. This study paves a new way for the universal fabrication of bimetallic hollow structured nanomaterials as efficient electrocatalysts for boosting the HER.

Plasmonic Hybrid Nanostructures in Photocatalysis: Structures, Mechanisms, and Applications

(Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term "hybrid" implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core-shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H₂ generation, CO₂ reduction, water purification, air purification, and disinfection.

Ruthenium-nickel-cobalt alloy nanoparticles embedded in hollow carbon microtubes as a bifunctional mosaic catalyst for overall water splitting

The development of efficient bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for reducing the cost of hydrogen production by water splitting. Herein, hollow microtubes composed of RuNi₁Co₁ alloy nanoparticles uniformly embedded in the carbon matrix (RuNi₁Co₁@CMT) are prepared through a simple impregnation followed by reduction. Benefiting from the unique mosaic structure and the synergistic effect between Ru and NiCo, RuNi₁Co₁@CMT achieves more exposed active sites and improved reaction kinetics. As a consequence, RuNi₁Co₁@CMT exhibits considerable catalytic activities with the overpotentials of 78 mV for HER and 299 mV for OER at 10 mA cm^-2 in 1 M KOH. In addition, RuNi₁Co₁@CMT exhibits excellent stability for up to 30 h in both HER and OER processes at 20 mA cm^-2, which is attributed to the protection of the RuNi₁Co₁ alloy particles by the carbon layer. Furthermore, the assembled RuNi₁Co₁@CMT || RuNi₁Co₁@CMT overall water splitting system shows a cell voltage of 1.58 V at 10 mA cm^-2. The density functional theory (DFT) calculations indicate that the addition of Ru can optimize the hydrogen adsorption free energy of Ni and Co sites. Finally, a solar panel-driven water splitting device is built, which can realize green and sustainable hydrogen production. The fabrication of RuNi₁Co₁@CMT provides a new way for the preparation of effective alloy nanomaterials for energy storage and conversion.

Can Hardware Removal be Avoided Using Bioresorbable Mg-Zn-Ca Screws After Medial Malleolar Fracture Fixation? Mid-Term Results of a First-In-Human Study

Ankle is the most common site of hardware removal, mainly performed within 12 months of the primary surgery. The prominence of the metallic hardware is a frequent cause of pain after fracture fixation. Over the last decade, the development of bioresorbable materials based on magnesium (Mg) has increased. Bioresorbable metals aim to avoid a second surgery for hardware removal.

METHODS

Twenty patients with isolated, bimalleolar, or trimalleolar ankle fractures were treated with bioresorbable screws made of Mg, 0.45wt% calcium (Ca) and 0.45wt% zinc (Zn) (ZX00). Patient-reported outcome measures (PROMs) including visual analogue scale (VAS) for pain, the presence of complications 6 and 12 months after surgery and the AOFAS scale after 12 months were reported. The functional outcomes were analysed through the range of motion (ROM) of the ankle joint with a standard goniometer. Degradation products and the bioresorbability of the screws were evaluated using plane radiographs.

RESULTS

One patient was lost to follow-up. All patients were free of pain, no complications, shoe conflict or misalignement were reported after 12 months of follow-up. No Mg screws were surgically removed. An additional fixation of the distal fibula or the dorsal tibial fragment with conventional titanium implants (Ti) was performed in 17 patients. Within 12 months after primary refixation, 12 of these patients (71%) underwent a second surgery for Ti hardware removal. The mean AOFAS score was 89.8±7.1 and the difference between the treated and the non-treated site in the ROM of the talocrural joint was 2°±11° after 12 months. Radiolucent areas around the screws were attributed to degradation and did not affect clinical or functional outcomes. After one year, the Mg screw heads could not be detected in the plane radiographs of 17 patients which suggests that the majority of the screw head is degraded without introducing adverse reactions.

CONCLUSIONS

At 6 and 12 months, the bioresorbable Mg screws show excellent PROMs without complications or need for screw removal. The resorbability of the screw heads in most of the patients after one year could also provide an advantage over conventional bio-inert implants by avoiding related skin irritation due for instance to shoe conflict.

In vivo kinetic release of five metal ions (iron, titanium, nickel, copper, and chromium) from fixed orthodontic alloys in Erbil city-Kurdistan region/Iraq

The orthodontic kinetic release of metal ions was studied in order to have a conclusive in vivo data for variation of metal ion concentrations with time (month) at normal oral temperature 37°C, which affects the saliva quality and quantity, pH, and chemical and physical characteristics of food and liquid. The superficial breakdown and release of metals from the alloy brackets were investigated by scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDS) images. The kinetic release experiment of the metal ion concentrations (nickel, chromium, titanium, iron, and copper) in the saliva uptakes follows a pseudo-second-order kinetic model; the release rate of metal ions was in series Fe²⁺ > Ti²⁺ > Ni²⁺ > Cu²⁺ > Cr³⁺, and the highest saliva pH and flow rate were detected after 1 month for fixed orthodontics appliance was (7.16 ± 0.55) and (0.88 ± 0.55) respectively.

Boron, nitrogen co-doped biomass-derived carbon aerogel embedded nickel-cobalt-iron nanoparticles as a promising electrocatalyst for oxygen evolution reaction

The electrocatalytic performance of oxygen evolution reaction (OER) electrocatalysts is highly reliant on the activity of its catalytic active site, which may be augmented by raising the number of active sites. In this study, nanoscaled nickel-cobalt-iron (NiCoFe) alloy was embedded on conductive boron(B), nitrogen(N) co-doped/biomass-derived carbon aerogel as an OER electrocatalyst. The synthesized electrocatalysts were calcined under different temperatures and with variable dopants. The optimal electrocatalyst (BN/CA-NiCoFe-600) demonstrated a low overpotential of 321 mV (at current density of 10 mA cm^-2) and a minute Tafel slope of 42 mV dec^-1, which was even smaller than that of IrO₂ and RuO₂. Its mass activity and specific activity were calculated to be 201.7 A g^-1, and 34.1 cm^-2_ECSA, respectively. Furthermore, the electrocatalyst showed excellent stability and durability. This work provides an easy and practical synthetic strategy for acquiring very active and durable electrocatalysts for OER.

High-quantum yield alloy-typed core/shell CdSeZnS/ZnS quantum dots for bio-applications

Background

Quantum dots (QDs) have been used as fluorophores in various imaging fields owing to their strong fluorescent intensity, high quantum yield (QY), and narrow emission bandwidth. However, the application of QDs to bio-imaging is limited because the QY of QDs decreases substantially during the surface modification step for bio-application.

Results

In this study, we fabricated alloy-typed core/shell CdSeZnS/ZnS quantum dots (alloy QDs) that showed higher quantum yield and stability during the surface modification for hydrophilization compared with conventional CdSe/CdS/ZnS multilayer quantum dots (MQDs). The structure of the alloy QDs was confirmed using time-of-flight medium-energy ion scattering spectroscopy. The alloy QDs exhibited strong fluorescence and a high QY of 98.0%. After hydrophilic surface modification, the alloy QDs exhibited a QY of 84.7%, which is 1.5 times higher than that of MQDs. The QY was 77.8% after the alloy QDs were conjugated with folic acid (FA). Alloy QDs and MQDs, after conjugation with FA, were successfully used for targeting human KB cells. The alloy QDs exhibited a stronger fluorescence signal than MQD; these signals were retained in the popliteal lymph node area for 24 h.

Conclusion

The alloy QDs maintained a higher QY in hydrophilization for biological applications than MQDs. And also, alloy QDs showed the potential as nanoprobes for highly sensitive bioimaging analysis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01227-2.

Effect of alloy elements on iridium shear modulus by Ab initio analysis

The effect of the addition of rhodium (Rh), rhenium (Re), tungsten (W), gold (Au), and platinum (Pt) on the shear modulus of face-centered cubic iridium (Ir) was investigated using an ab initio method. The shear modulus was calculated using the second derivative of the strain energy with respect to strain. It was found that both the bulk modulus (G) and the ratio (G/B) between bulk and shear modulus decreased with the addition of elements to the Ir, which meant that all five of these alloy elements lowered the brittleness of the bulk Ir. The decreased shear modulus was the main factor for the lowered brittleness. And the decreasing order of shear modulus in the [112] and [100] crystalline directions was Ir > Rh > Pt > W = Au > Re and Ir > W > Rh > Pt > Au > Re respectively. The reason for the order was both the atomic distance and the bond strength between alloy atoms and Ir atoms. The larger bond strength meant the larger shear modulus, and the smaller atomic distance meant the smaller shear modulus.

"Self-doping" defect engineering in SnP3@gamma-irradiated hard carbon anode for rechargeable sodium storage

Reasonable design of defect engineering in the electrode materials for sodium-ion batteries (SIBs) can significantly optimize battery performance. Here, compared with the traditional "foreign-doping" defects method, we report an innovative gamma-irradiation technique to introduce the "self-doping" defects in the popcorn hard carbon (HC). Considering the advantages of adsorption-intercalation-alloying sodium storage mechanism, the defect-rich HC-coated alloy structure (SnP₃@HC-γ) was integrated. Due to the high energy and strong penetrability of γ-rays, the constructed "self-doping" defect engineering effectively expands the interlayer structure of HC and forms the irregular ring structure. Simultaneously, the exposed large number of coordination unsaturated sites can accelerate the reaction kinetics on the surface. Based on the synergistic effect of the SnP₃@HC-γ, the composites exhibit an excellent reversible capacity of 668 mAh g^-1 at 0.1 A g^-1 in SIBs. Even, after 400 cycles at 1.0 A g^-1, an exceptional cyclability with 88% capacity retention (430 mAh g^-1) can be maintained. We envision that the γ-irradiation technology used in this research not only overturns the general perception that "self-doping" defects will reduce performance, but also provides reliable technical support for large-scale construction of high-defect, high-capacity and stable sodium-ion anode materials.

Retention forces between primary and secondary CAD/CAM manufactured telescopic crowns: an in vitro comparison of common material combinations

OBJECTIVES

To analyze the retention forces between primary and secondary telescopic crowns milled from various materials and to compare them with the retention forces between cast telescopic crowns made of precious metal alloys.

MATERIALS AND METHODS

Primary and secondary crowns (N = 60; n = 10 per group) were fabricated using various material combinations (1: zirconia [ZIR]/polyether ether ketone [PEEK]; 2: titanium grade IV [TI]/PEEK; 3: PEEK/PEEK; 4: non-precious alloy [NPA]/PEEK; 5:NPA/NPA), while precious alloy (PA) was used for the control group (6: PA/PA). The retention forces at 10, 1000, 5000, and 10,000 connection and disconnection cycles and the relative weights were analyzed, applying nonparametric repeated measures ANOVA and post hoc Mann-Whitney and Wilcoxon signed-rank tests (α < 0.05).

RESULTS

Globally, significant differences in the retention forces among the materials (p < 0.0001), time points (p < 0.0001), and wear resistance for the various materials (p < 0.0001) were observed. No significant changes in retention forces compared to baseline were observed in groups 2, 4, 5, and 6. A significantly higher weight loss for both primary and secondary crowns was observed in groups 4 and 6.

CONCLUSIONS

The material combination in telescopic attachments influences retention forces and wear. Interactions between materials and time were evident, indicating that the change in retention forces differs among the materials. The combinations of milled TI/PEEK and NPA/NPA qualify for further preclinical testing in a more clinically realistic setup, determining a material-specific double-crown design.

CLINICAL RELEVANCE

The design of precious alloy telescopic crowns cannot be directly transferred to other milled material combinations due to different retention behaviors.

Effect of surface deformation on biocompatibility of biomedical alloys

In this study, biocompatibility of Co-29Cr-5Mo (CCM), 316L steel (316L) and Ti-6Al-4V (TC4) alloys after surface plastic deformation under the condition comparable to the human ankle activities were investigated in details. Biocompatibility of all alloys decreases after surface deformation, while it is most significantly observed in CCM alloy. The different responses of biocompatibility are related to the corresponding microstructure evolution during surface deformation: martensitic phase transformation, dislocation slipping and mechanical twinning in CCM alloy result in the extremely localized microstructure, giving rise to the obviously decreased corrosion resistance or biocompatibility; quite homogenous microstructure after surface deformation leads to the slightly decreased corrosion resistance or biocompatibility in both 316L and TC4 alloys, since the surface deformation is dominated by slipping in 316L and by both slipping and a few mechanical twinning in TC4.

Implant Material Sciences

In the past, the only way to replace missing teeth was to have a removable appliance. However, these days, dental implants are commonly being used to replace missing teeth. The dental implants are improving as a result of new technological and scientific advances. Different materials have been used in the past for dental implants such as lead, stainless steel, and gold. Currently, the focus is on using Roxolid, surface-modified titanium implants, and zirconia. These materials have superior esthetic and functional characteristics for dental implants.

Voltammetric determination of hydrogen peroxide using AuCu nanoparticles attached on polypyrrole-modified 2D metal-organic framework nanosheets

AuCu/PPy/Cu-TCPP nanocomposites were synthesized by attaching AuCu nanoparticles to a polypyrrole (PPy)-modified 2D Cu-TCPP metal-organic framework nanosheet; Cu-TCPP can exhibit catalytic activity for the reduction of H₂O₂. Based on the nanocomposite, a new method for the determination of H₂O₂ was established. The morphology of the AuCu/PPy/Cu-TCPP was analyzed by transmission electron microscopy. Cu-TCPP exhibited a 2D nanosheet with obvious wrinkles, and a large amount of AuCu was uniformly attached to PPy/Cu-TCPP. The composition and structure were studied by X-ray diffraction, FTIR, and X-ray photoelectron spectroscopy. At the optimal working potential and scan rate of - 0.55 V(vs. SCE) and 100 mV/s, respectively, electrochemical studies indicated that in N₂-saturated supporting electrolyte, the method showed good catalytic performance for H₂O₂, with a detection limit of 6.67 nM (S/N = 3), a linear range of 7.10 μM-24.10 mM, and a sensitivity of 35.0 μA mM^-1 cm². Compared to H₂O₂ methods based on related materials, this method exhibits a wide linear range, and the detection limit is down to nanomolar. Graphical abstract Schematic presentation of the preparation of AuCu/PPy/Cu-TCPP nanocomposites. AuCu/PPy/Cu-TCPP nanocomposite was prepared by loading gold-copper (AuCu) bimetallic nanoparticles with good catalytic properties on two-dimensional copper (II)-porphyrin (Cu-TCPP) nanosheet metal-organic framework material, whose conductivity was improved by polypyrrole (PPy). A method for the determination of hydrogen peroxide by voltammetric was established.

Corrosion inhibition of brass 60Cu-40Zn in 3% NaCl solution by 3-amino-1, 2, 4-triazole-5-thiol

In this article, we tested a new organic molecule used as a corrosion inhibitor of the 60Cu–40Zn alloy in an aqueous solution similar to sea water 3% NaCl namely 3-amino-1,2,4-triazole-5-thiol (ATT) using stationary and transient electrochemical methods (polarization curves and electrochemical impedance spectroscopy (EIS)). In addition, the metal surface analysis was performed by the scanning electron microscopy (SEM) coupled with the X-ray dispersion energy (EDX) in the absence and in the presence of the inhibitor tested. Analysis of the polarization curves reveals that the ATT acts as a mixed inhibitor, while the inhibition efficiency reaches a value of 97% for a concentration of 1mM of ATT, these results are confirmed by the EIS techniques, indicating that the value of the charge transfer resistance increases with increasing of ATT concentrations, consequently the inhibitory efficiency increases and reaches a maximum value of 99% in the presence of 1mM of ATT. the influence of the immersion time shows that the corrosion inhibition of the brass 60Cu–40Zn improves with the increase of the immersion time and that the molecule adsorbs chemically and follows the Langmuir isotherm. SEM/EDS study confirms the presence of protective film on the Brass surface.

New target with low photoneutron yield for LINAC radiotherapy applications

This paper presents three new materials composed of Ti_XV_0,035XCu_X-1,035 (X = 2, 4 and 6%), is proposed as Linear Accelerator target. Its response to electron beam based on photoneutron production, is assessed by MC simulation and nuclear track-etch methodology. The outcome is compared to a tungsten target irradiated by energetic 16 MeV electron beam. Photoneutron yield, of two energy groups (thermal and epithermal) were determined via converter matter ¹⁰B (98%) and Cd-filter by PADC-track density comparison. The multi-metal Ti₂V_0,07Cu_97.93 target related to therapy beam quality, resulted advantageous in comparison to that provided by W-target, commonly used in the LINAC.

Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy

PURPOSE

The present study was designed to examine the clinical fit of fixed dental prosthesis fabricated by the milling-sintering method using a presintered cobalt-chromium alloy.

MATERIALS AND METHODS

Two single metal-ceramic crowns were fabricated via milling-sintering method and casting method in each of the twelve consecutive patients who required an implant-supported fixed prosthesis. In the milling-sintering method, the prosthetic coping was designed in computer software, and the design was converted to a non-precious alloy coping using milling and post-sintering process. In the casting method, the conventional manual fabrication process was applied. The absolute marginal discrepancy of the prostheses was evaluated intraorally using the triple-scan technique. Statistical analysis was conducted using Mann-Whitney U test (α=.05).

RESULTS

Eight patients (66.7%) showed a lower marginal discrepancy of the prostheses made using the milling-sintering method than that of the prosthesis made by the casting method. Statistically, the misfit of the prosthesis fabricated using the milling-sintering method was not significantly different from that fabricated using the casting method (P=.782). There was no tendency between the amount of marginal discrepancy and the measurement point.

CONCLUSION

The overall marginal fit of prosthesis fabricated by milling-sintering using a presintered alloy was comparable to that of the prosthesis fabricated by the conventional casting method in clinical use.

Nanoporous platinum-copper flowers for non-enzymatic sensitive detection of hydrogen peroxide and glucose at near-neutral pH values

Multimodal nanoporous PtCu flowers (np-PtCu) were prepared via a two-step dealloying strategy under mild conditions. The np-PtCu alloy possesses an interconnected flower-like network skeleton with multiscale pore distribution. This material was placed on a glassy carbon electrode where it shows outstanding detection performance towards hydrogen peroxide and glucose in near-neutral pH solutions. It can be attributed to the specific structure in terms of interconnected nanoscaled ligaments, rich pore openings and a synergistic alloying effect. Figures of merit for detection H₂O₂ assay include (a) a working voltage of 0.7 V (vs. the reversible hydrogen electrode); (b) a wide linear response range (from 0.01 to 1.7 mM), and (c) a low detection limit (0.1 μM). The respective data for the glucose assay are (a) 0.4 V, (b) 0.01-2.0 mM, and (c) 0.1 μM. The method is not interfered in the presence of common concentrations of dopamine, acetaminophen and ascorbic acid. Graphical abstract Multimodal nanoporous (np) PtCu alloy was prepared via a two-step dealloying strategy under mild conditions. Np-PtCu exhibits superior electrocatalytic activity. The assay is highly sensitive, selective, and it allows for a long-term detection of H₂O₂ and glucose.

Proposing an intelligent approach for measuring the thickness of metal sheets independent of alloy type

Radiation based gauges have been widely utilized as a nondestructive and robust tool for measuring the thickness of metal sheets in industry. The typical radiation thickness meter can just work accurately when the composition of the material is fixed during the measurement process. In conditions that material composition may differ substantially from the nominal composition, such as manufacturing rolled metals factories, the thickness measurements would be along with errors. The purpose of the present research is resolving the problem of measuring the thickness of metal sheets with various alloys. The aluminum is investigated in this work as a case study but the procedure can be applied for other types of metals. As the first step, the performance of various arrangements of two main detection techniques, named dual energy and dual modality, were investigated using MCNPX code to obtain optimum technique and arrangement. The simulation results indicated that a binary combination of ²⁴¹Am-⁶⁰Co isotopes as the source and one transmission detector in dual energy technique is the most appropriate choice. After then, an experimental setup based on the obtained optimal technique from simulation investigations was established. The aluminum sheets with 4 alloy types of 1050, 3105, 5052 and 6061 and thicknesses in the range of 0.2-4 cm with a step of 0.2 cm were tested and the obtained data were implemented for testing and training the artificial neural network (ANN). The proposed methodology could predict the thickness of aluminum sheet independent of its alloy type with an error of less than 0.04 cm in experiments.

Bioaccessibility and relative oral bioavailability of cobalt and nickel in residential soil and dust affected by metal grinding operations

Including measures of relative bioavailability (RBA) improves the accuracy of site-specific risk assessment when evaluating metals bound in matrices that resist acid digestion (alloys, slag, tailings). In vitro gastrointestinal bioaccessibility and in vivo RBA assessments were conducted using baghouse dust, surface dust, and soil collected in a neighborhood near a metal forge, which emitted metals in the form of corrosion resistant alloys. The study objective was to characterize the in vitro bioaccessibility and relative bioavailability (RBA) of cobalt and nickel when ingested as freely soluble forms (ionic salts used as the basis for oral toxicity criteria), compared to when incidentally ingested in the forms found in the environment. Test materials and standard reference materials-cobalt chloride and nickel sulfate-were administered daily for 14 or 21 days, twice daily, to juvenile swine. Daily intake doses for cobalt were ≤229 μg/kg-day, and for nickel, ≤1419 μg/kg-day. Concentrations of cobalt and nickel were measured in various tissues; 24-hour urinary excretion of each metal was also measured. Multiple linear regression modeling was performed for tissue concentration or urinary excretion vs. dose in each material, with weighting as inverse variance in each dose group. Liver, urine, and kidney provided the optimal data. Although RBA values were affected by limited absolute bioavailability of cobalt and nickel in reference materials, trends across the different biological matrices consistently showed significantly reduced bioavailability of cobalt and nickel in soil and dust, with RBAs ranging from 0.2% to 12%. Bioaccessibility of cobalt and nickel in soil and dust were 1% to 5%, and similar results were found for baghouse dust. The data demonstrate that cobalt and nickel in soil and dust affected by alloys are resistant to bioelution and absorption. This study provides useful information for site-specific risk assessments and insights for planning future research.

Influence of proteins on the corrosion behavior of a chitosan-bioactive glass coated magnesium alloy

The current study explored the degradation behavior of a WE43 Mg alloy during immersion tests in Dulbecco's Modified Eagle's Medium (DMEM) for 3d and 7d, for a bare alloy surface as well as for samples with surface pre-treatment, and finally for samples coated with chitosan-bioactive glass. The immersion tests were conducted with and without addition of serum, to study the influence of proteins on the degradation process. Mass-loss was measured to determine the corrosion rate after 3d and 7d of immersion. The samples were analyzed by SEM with respect to their surface morphology and the chemical composition was screened by high-resolution XPS. The results demonstrate not only a significant, time-dependent influence of serum addition on the corrosion behavior of the materials studied, but noteworthy is that depending on the sample type, proteins in solution were observed to either accelerate or inhibit corrosion. These results are discussed in correlation to observed changes in surface chemistry taking place upon immersion in the absence and presence of proteins.

Composition dependent activity of PdAgNi alloy catalysts for formic acid electrooxidation

In the present study, the carbon supported Pd, PdAg and PdAgNi (Pd/C, PdAg/C and PdAgNi/C) electrocatalysts are prepared via NaBH₄ reduction method at varying molar atomic ratio for formic acid electrooxidation. These as-prepared electrocatalysts are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), N₂ adsorption-desorption, and X-ray electron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and lineer sweep voltammetry (LSV). While Pd₅₀Ag₅₀/C exhibits the highest catalytic activity among the bimetallic electrocatalyst, it is observed that Pd₇₀Ag₂₀Ni₁₀/C electrocatalysts have the best performance among the all electrocatalysts. Its maximum current density is about 1.92 times higher than that of Pd/C (0.675 mA cm^-2). Also, electrochemical impedance spectroscopy (EIS), chronoamperometry (CA) and lineer sweep voltammetry (LSV) results are in a good agreement with CV results in terms of stability and electrocatalytic activity of Pd₅₀Ag₅₀/C and Pd₇₀Ag₂₀Ni₁₀/C. The Pd₇₀Ag₂₀Ni₁₀/C catalyst is believed to be a promising anode catalyst for the direct formic acid fuel cell.

A novel method for vanadium slag comprehensive utilization to synthesize Zn-Mn ferrite and Fe-V-Cr alloy

Vanadium slag is a by-product from steelmaking process of vanadium-titanium magnetite, which mainly contains FeO, MnO, V₂O₃, and Cr₂O₃, The elements Fe and Mn are major components of Mn-Zn ferrite. The elements V and Cr are major components of V-Cr alloy. In view of the potential application in these study, a Mn_0.8Zn_0.2Fe₂O₄ of high saturation magnetization (Ms = 68.6 emu/g) and low coercivity (Hc = 3.3 Oe) was successfully synthesized from the leaching solutions of vanadium slag by adding appropriate chemical reagents, ZnCl₂ and MnCl₂·4H₂O, via roasting at 1300 °C for 1 h. The minor components (CaO and SiO₂) in the leaching solution of vanadium slag segregated to the grain boundaries resulting in increasing the resistivity of ferrite. The value of DC resistivity of Mn_0.8Zn_0.2Fe₂O₄ at 25 °C reached 1230.7Ω m. The residue containing Fe, V and Cr was chlorinated by AlCl₃ and the Fe³⁺, V³⁺, and Cr³⁺ ions were released into the NaCl-KCl eutectic. The current-time curve for the electrolysis of molten salt was investigated. Alloy (Fe, V, and Cr) of granular shape was obtained. The residue can be used to produce the mulite. This process provided a new approach to utilize slag from steelmaking.

Microstructured prealloyed Titanium-Nickel powder as a novel nonenzymatic hydrogen peroxide sensor

At present, commercial pure Titanium (Ti) and microstructured pre-alloyed Titanium-Nickel (TiNi) powders are employed as a sensitive electrochemical hydrogen peroxide (H₂O₂) sensor. Surface characterization of these materials are performed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical characterization is achieved via cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) on Ti and TiNi modified glassy carbon electrode (GCE). The electrochemical behavior of H₂O₂ at the pure Ti/GCE and microstructure pre-alloyed TiNi/GCE are studied by CV in 0.1 M phosphate buffer solution (PBS) containing as the supporting electrolyte. In addition, CA is employed for the determination of H₂O₂ at the applied potential of 0 V vs. Ag/AgCl. The sensor has a linear response range of 0.5-17.5 mM with a sensitivity of 280 µA mM^-1 cm^-2. Moreover, the limit of detection (LOD) and limit of quantification (LOQ) are 0.5 µM and 1.7 µM, respectively. The electrochemical sensor exhibits fast and selective responses to H₂O₂ concentration. The applicability of the sensor is checked using a hair coloring as a real sample with satisfactory results.

Effect of Implant Diameter And Alloy on Peri-Implant Strain: An In Vitro Quantitative Strain Analysis

This study aimed to evaluate the impact of implant diameter and alloy on peri-implant strains. Three implant types were investigated: regular commercially pure titanium (RcpTi), narrow commercially pure titanium (NcpTi) and narrow titanium-zirconium alloy (NTi-Zr) implants. Strain gauge models were fabricated from epoxy resin. All the implants were loaded in identical fashion. The greatest peri-implant strains were recorded around NTi-Zr implants, followed by NcpTi implants. The RcpTi implants were associated with the least strain values. The difference between the implant types was significant. Therefore, it can be concluded that the implant diameter and material can influence the peri-implant strain magnitude.

Effect Of Cobalt-Chromium Alloy Re-Use In Dentistry On Its Castability Value

BACKGROUND

Re-use of dental casting alloy is a routine practice, which is carried out with the motive to conserve resources. There have been studies on the re-use of alloys but a controversy exists as to the proportioning ratio of fresh to used alloy and the number of time an alloy can be recast. The objective of the study was to measure the effect of addition of 50% by weight used alloy to the fresh Cobalt-Chromium alloy on the castability.

METHODS

In the present in-vitro experimental study A total of 20 specimens were cast by flame centrifuge, using modified Whitlock's method. The total sample size was divided into four groups of five specimens each. Group 1 was the control group with 100% fresh alloy cast once. In group 2, 3 and 4, a 50% by weight cut off of previous castings were mixed to the fresh alloy. The reused alloy for the group 2 and 3 was further aged or exposed to flame casting separately. The number of completely cast segments were counted and castability value was calculated according to the Whitlock's formula.

RESULTS

There was no significant difference of castability value among the entire tested group (p=0.085).

CONCLUSIONS

Within the limitations of the present study, it is recommended that commercial Co-Cr-Mo alloy can be re-used six times without affecting its castability, when 50% fresh alloy is added on each re-use.

Synthesis, Study, and Discrete Dipole Approximation Simulation of Ag-Au Bimetallic Nanostructures

Water-soluble Ag-Au bimetallic nanostructures were prepared via co-reduction and seed-mediated growth routes employing poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA) as both a reductant and a stabilizer. Ag-Au alloy nanoparticles were obtained by the co-reduction of AgNO3 and HAuCl4, while Ag-Au core-shell nanostructures were prepared through seed-mediated growth using PSSMA-Au nanoparticle seeds in a heated AgNO3 solution. The optical properties of the Ag-Au alloy and core-shell nanostructures were studied, and the growth mechanism of the bimetallic nanoparticles was investigated. Plasmon resonance bands in the range 422 to 517 nm were observed for Ag-Au alloy nanoparticles, while two plasmon resonances were found in the Ag-Au core-shell nanostructures. Furthermore, discrete dipole approximation theoretical simulation was used to assess the optical property differences between the Ag-Au alloy and core-shell nanostructures. Composition and morphology studies confirmed that the synthesized materials were Ag-Au bimetallic nanostructures.

Chitosan stabilized Ag-Au nanoalloy for colorimetric sensing and 5-Fluorouracil delivery

Fluorescent CS/Ag-Au (chitosan/silver-gold) nanocomposite containing different weight percentage of Ag and Au was synthesized using the chemical reduction method. 5-Fluorouracil (5-FU) encapsulated nanocomposite was also synthesized and its cytotoxicity towards breast cancer cell lines (MCF-7) studied. The XRD pattern of the nanocomposite shows peaks of chitosan, silver and gold. The peaks corresponding to gold and silver indicate the face centered cubic structure of silver and gold nanoparticles. The polymer matrix nanocomposite structure with chitosan as the matrix and silver-gold as the filler phase is evident from the high resolution transmission electron microscopy (HRTEM) images and an increase in particle size from∼5nm to about 12nm is noticeable on encapsulation of 5-Fluorouracil (5-FU). The presence of fluorine in the case of 5-FU encapsulated nanocomposite and the presence of reflections corresponding to 5-FU in the SAED pattern confirms the encapsulation of 5-FU into the nanocomposite, which is also confirmed by elemental mapping. The presence of a single surface plasmon resonance (SPR) peak in the case of the nanocomposite in a position in between the SPR bands of pure silver and gold nanoparticles confirms the formation of Ag-Au alloy and the elemental mapping results obtained for the nanocomposite also supports the UV-vis results. The photoluminescence (PL) spectrum clearly shows an emission peak in the near infrared region (700-900nm), which makes the nanocomposite suitable for use in cellular imaging. The application of the nanocomposite as a colorimetric sensor was also studied and it was found to be useful for the specific detection of mercury (Hg) without much interference and the detection limit was found to be 5.0×10^-8M.

Long-term in vivo degradation behavior and near-implant distribution of resorbed elements for magnesium alloys WZ21 and ZX50

We report on the long-term effects of degrading magnesium implants on bone tissue in a growing rat skeleton using continuous in vivo micro-Computed Tomography, histological staining and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Two different magnesium alloys-one rapidly degrading (ZX50) and one slowly degrading (WZ21)-were used to evaluate the bone response and distribution of released Mg and Y ions in the femur of male Sprague-Dawley rats. Regardless of whether the alloy degrades rapidly or slowly, we found that bone recovers restitutio ad integrum after complete degradation of the magnesium implant. The degradation of the Mg alloys generates a significant increase in Mg concentration in the cortical bone near the remaining implant parts, but the Mg accumulation disappears after the implant degrades completely. The degradation of the Y-containing alloy WZ21 leads to Y enrichment in adjacent bone tissues and in newly formed bone inside the medullary space. Locally high Y concentrations suggest migration not only of Y ions but also of Y-containing intermetallic particles. However, after the full degradation of the implant the Y-enrichment disappears almost completely. Hydrogen gas formation and ion release during implant degradation did not harm bone regeneration in our samples.

STATEMENT OF SIGNIFICANCE

Magnesium is generally considered to be one of the most attractive base materials for biodegradable implants, and many magnesium alloys have been optimized to adjust implant degradation. Delayed degradation, however, generates prolonged presence in the organism with the risk of foreign body reactions. While most studies so far have only ranged from several weeks up to 12months, the present study provides data for complete implant degradation and bone regeneration until 24months, for two magnesium alloys (ZX50, WZ21) with different degradation characteristics. μCT monitoring, histological staining and LA-ICP-MS illustrate the distribution of the elements in the neighboring bony tissues during implant degradation, and reveal in particular high concentrations of the rare-earth element Yttrium.

Effect of external magnetic field on the Kβ/Kα X-ray intensity ratios of TixNi1-x alloys excited by 59.54 and 22.69keV photons

The effects of external magnetic field and exciting photon energies on the Kβ/Kα X-ray intensity ratios of various alloy compositions of Ti-Ni transition metal alloys have been investigated in this work using X-ray fluorescence spectroscopy. The spectrum of characteristic K-X-ray photons from pure Ti, pure Ni and TixNi1-x (x=0.30; 0.40; 0.50; 0.60; 0.70) alloys were detected with a high resolution Si (Li) solid-state detector. Firstly, Kβ/Kα X-ray intensity ratios of pure Ti, pure Ni and TixNi1-x alloys were measured following excitation by 59.54keV γ-rays from a 200mCi (241)Am radioactive point source without any magnetic field and under 0.5 and 1T external magnetic fields, separately. Later, the same measurements were repeated under the same experimental conditions for 22.69keV X-rays from a 370 MBq(1)(0)(9)Cd radioactive point source. The results obtained for Kβ/Kα X-ray intensity ratios of pure Ti, pure Ni, Ti and Ni in various Ti-Ni alloys were evaluated in terms of both external magnetic field effect and exciting photon energy effect. When the results obtained for both exciting photon energies are evaluated in terms of changing of Kβ/Kα X-ray intensity ratios depending on the alloy composition, the tendency of these changes are observed to be similar. Also, Kβ/Kα X-ray intensity ratios for all samples examined have changed with increasing external magnetic field. Therefore, the results obtained have shown that Kβ/Kα X-ray intensity ratios of Ti and Ni in TixNi1-x alloys are connected with the external magnetic field. The present study makes it possible to perform reliable interpretation of experimental Kβ/Kα X-ray intensity ratios for Ti, Ni and TixNi1-x alloys and can also provide quantitative information about the changes of the Kβ/Kα X-ray intensity ratios of these metals with alloy composition.

An ultrasensitive SiO2-encapsulated alloyed CdZnSeS quantum dot-molecular beacon nanobiosensor for norovirus

Ultrasensitive, rapid and selective diagnostic probes are urgently needed to overcome the limitations of traditional probes for norovirus (NV). Here, we report the detection of NV genogroup II via nucleic acid hybridization technology using a quantum dot (QD)-conjugated molecular beacon (MB) probe. To boost the sensitivity of the MB assay system, an ultrasensitive QD fluorophore with unique optical properties was synthesized, characterized and exploited as a fluorescence signal generator. Alloyed thioglycolic (TGA)-capped CdZnSeS QDs with a high photoluminescence (PL) quantum yield (QY) value of 92% were synthesized, and a modified silanization method was employed to encapsulate the thiol-capped QDs in a silica layer. The resulting highly luminescent alloyed SiO2-coated CdZnSeS QDs had a remarkable PL QY value of 98%. Transmission electron microscopy and dynamic light scattering confirmed the monodispersity of the alloyed nanocrystals, and zeta potential analysis confirmed their colloidal stability. Powder X-ray diffraction and PL lifetime measurements confirmed the surface modification of the QDs. The alloyed TGA-capped and SiO2-coated CdZnSeS QD-conjugated MB bioprobes detected extremely low concentrations of NV RNA. Ultrasensitive detection of low concentrations of NV RNA with a limit of detection (LOD) of 8.2copies/mL in human serum and a LOD of 9.3 copies/mL in buffer was achieved using the SiO2-coated CdZnSeS QD-MB probes, an increase in sensitivity of 3-fold compared with the detection limit for NV RNA using TGA-capped CdZnSeS QD-MBs. The additional merits of our detection system are rapidity, specificity and improved sensitivity over conventional molecular test probes.

[Non-antagonistic influence of Krumeich's intrastromal corneal ring in an experimental tissue culture system]

BACKGROUND

Intrastromal insertion of Krumeich's corneal ring between graft and residual host corneal tissue appears to impair preripheral, superficial and superfluous vascularization of donor corneal tissue.

OBJECTIVES

The purpose of this study was to investigate the cytotoxic effects of Krumeich's ring using tissue cultures composed of primary human dermal microvascular endothelial cells from adult donors (HMVEC).

MATERIALS AND METHODS

Soluble growth medium extracts of the individual components of Krumeich's ring alloy were prepared and HMVEC were exposed to these extracts in triplicate for 1 day followed by investigation with 3‑(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Furthermore, HMVEC were cultured for 5 days on either Krumeich's ring or polypropylene (PP) discs coated with individual components of the Krumeich's ring alloy followed by double vital staining with fluorescein diacetate (FDA) and propidium iodide (PI).

RESULTS

The MTT assays revealed that higher doses of the extracts appeared to reduce the viability of HMVEC, while highly diluted extracts of molybdenum (Mo) powder appeared to increase the metabolic activity of HMVEC. The FDA-PI staining showed only a few live HMVEC on either cobalt (Co) or Mo-coated PP discs, compared to the respective titanium (Ti) and chromium (Cr) counterparts. Viable HMVEC appeared to attach to Krumeich's ring after a 5‑day incubation period.

CONCLUSION

The results confirm that Krumeich's ring does not exert measurable cytotoxic effects in our chosen assay system. High dilutions of medium-soluble Mo powder extracts appear to increase the metabolic activity of HMVEC.

Long-term osseointegration of 3D printed CoCr constructs with an interconnected open-pore architecture prepared by electron beam melting

In orthopaedic surgery, cobalt chromium (CoCr) based alloys are used extensively for their high strength and wear properties, but with concerns over stress shielding and bone resorption due to the high stiffness of CoCr. The structural stiffness, principally related to the bulk and the elastic modulus of the material, may be lowered by appropriate design modifications, to reduce the stiffness mismatch between metal/alloy implants and the adjacent bone. Here, 3D printed CoCr and Ti6Al4V implants of similar macro-geometry and interconnected open-pore architecture prepared by electron beam melting (EBM) were evaluated following 26week implantation in adult sheep femora. Despite higher total bone-implant contact for Ti6Al4V (39±4%) than CoCr (27±4%), bone formation patterns were similar, e.g., densification around the implant, and gradual ingrowth into the porous network, with more bone in the outer half (periphery) than the inner half (centre). Raman spectroscopy revealed no major differences in mineral crystallinity, the apatite-to-collagen ratio, or the carbonate-to-phosphate ratio. Energy dispersive X-ray spectroscopy showed similar Ca/P ratio of the interfacial tissue adjacent to both materials. Osteocytes made direct contact with CoCr and Ti6Al4V. While osteocyte density and distribution in the new-formed bone were largely similar for the two alloys, higher osteocyte density was observed at the periphery of the porous network for CoCr, attributable to slower remodelling and a different biomechanical environment. The results demonstrate the possibility to achieve bone ingrowth into open-pore CoCr constructs, and attest to the potential for fabricating customised osseointegrated CoCr implants for load-bearing applications.

STATEMENT OF SIGNIFICANCE

Although cobalt chromium (CoCr) based alloys are used extensively in orthopaedic surgery, stress shielding due to the high stiffness of CoCr is of concern. To reduce the stiffness mismatch between CoCr and bone, CoCr and Ti6Al4V implants having an interconnected open-pore architecture were prepared by electron beam melting (EBM). After six months of submerged healing in sheep, both alloys showed similar patterns of bone formation, with densification around the implant and gradual ingrowth into the porous network. The molecular and elemental composition of the interfacial tissue was similar for both alloys. Osteocytes made direct contact with both alloys, with similar overall osteocyte density and distribution. The work attests to the potential for achieving osseointegration of EBM manufactured porous CoCr implants.

Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides

The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

The vibrational and configurational entropy of disordering in Cu3Au

The thermodynamics of disordering in Cu₃Au have been investigated by measuring the heat capacity of samples with different degrees of long- and short-range order between T = 5 and 720 K using relaxation and differential scanning calorimetry. The heat capacities of L1₂-ordered and fcc-disordered samples show similar behaviour at low temperatures (<300 K). They deviate positively from the linear combination of the end-member heat capacities between ∼30 and 160 K. However, small differences between the two samples exist, as the disordered sample has a larger heat capacity producing a vibrational entropy of disordering of ∼0.05 R. At temperatures higher than 300 K, the heat capacity of the ordered sample shows a prominent lambda-type anomaly at 675 K due to the diffusive L1₂-fcc phase transition. When starting these measurements with disordered samples, ordering effects are observed between 400 and 620 K, and the disordering reaction is observed at 660 K. Evaluation of the data gives an enthalpy and entropy of disordering at 683 K of 2.0 kJ mol^-1 and 0.39 R, respectively. However, these values increase with increasing temperature, thereby reducing the short-range order. Because the vibrational and configurational disordering effects become active at different temperature regimes, i.e., the vibrational effects at low temperatures (T ≪ 300 K) and the sum of both effects at higher temperatures (T > 300 K), they have been successfully separated.

Adding two active silver atoms on Au₂₅ nanoparticle

Alloy nanoparticles with atomic monodispersity is of importance for some fundamental research (e.g., the investigation of active sites). However, the controlled preparation of alloy nanoparticles with atomic monodispersity has long been a major challenge. Herein, for the first time a unique method, antigalvanic reduction (AGR), is introduced to synthesize atomically monodisperse Au25Ag2(SC2H4Ph)18 in high yield (89%) within 2 min. Interestingly, the two silver atoms in Au25Ag2(SC2H4Ph)18 do not replace the gold atoms in the precursor particle Au25(SC2H4Ph)18 but collocate on Au25, which was supported by experimental and calculated results. Also, the two silver atoms are active to play roles in stabilizing the alloy nanoparticle, triggering the nanoparticle fluorescence and catalyzing the hydrolysis of 1,3-diphenylprop-2-ynyl acetate.

Research and development of metals for medical devices based on clinical needs

The current research and development of metallic materials used for medicine and dentistry is reviewed. First, the general properties required of metals used in medical devices are summarized, followed by the needs for the development of α + β type Ti alloys with large elongation and β type Ti alloys with a low Young's modulus. In addition, nickel-free Ni-Ti alloys and austenitic stainless steels are described. As new topics, we review metals that are bioabsorbable and compatible with magnetic resonance imaging. Surface treatment and modification techniques to improve biofunctions and biocompatibility are categorized, and the related problems are presented at the end of this review. The metal surface may be biofunctionalized by various techniques, such as dry and wet processes. These techniques make it possible to apply metals to scaffolds in tissue engineering.

Tunable Visible Emission of Ag-Doped CdZnS Alloy Quantum Dots

Highly luminescent Ag-ion-doped Cd1-xZnxS (0 ≤ x ≤ 1) alloy nanocrystals were successfully synthesized by a novel wet chemical precipitation method. Influence of dopant concentration and the Zn/Cd stoichiometric variations in doped alloy nanocrystals have been investigated. The samples were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) to investigate the size and structure of the as prepared nanocrystals. A shift in LO phonon modes from micro-Raman investigations and the elemental analysis from the energy dispersive X-ray analysis (EDAX) confirms the stoichiometry of the final product. The average crystallite size was found increasing from 1.0 to 1.4 nm with gradual increase in Ag doping. It was observed that photoluminescence (PL) intensity corresponding to Ag impurity (570 nm), relative to the other two bands 480 and 520 nm that originates due to native defects, enhanced and showed slight red shift with increasing silver doping. In addition, decrease in the band gap energy of the doped nanocrystals indicates that the introduction of dopant ion in the host material influence the particle size of the nanocrystals. The composition dependent bandgap engineering in CdZnS:Ag was achieved to attain the deliberate color tunability and demonstrated successfully, which are potentially important for white light generation.

Nearly Monodispersion CoSm Alloy Nanoparticles Formed by an In-situ Rapid Cooling and Passivating Microfluidic Process

An in siturapid cooling and passivating microfluidic processhas been developed for the synthesis of nearly monodispersed cobalt samarium nanoparticles (NPs) with tunable crystal structures and surface properties. This process involves promoting the nucleation and growth of NPs at an elevated temperature and rapidly quenching the NP colloids in a solution containing a passivating reagent at a reduced temperature. We have shown that Cobalt samarium NPs having amorphous crystal structures and a thin passivating layer can be synthesized with uniform nonspherical shapes and size of about 4.8 nm. The amorphous CoSm NPs in our study have blocking temperature near 40 K and average coercivity of 225 Oe at 10 K. The NPs also exhibit high anisotropic magnetic properties with a wasp-waist hysteresis loop and a bias shift of coercivity due to the shape anisotropy and the exchange coupling between the core and the thin oxidized surface layer.

Effect of ZnCdTe-Alloyed Nanocrystals on Polymer-Fullerene Bulk Heterojunction Solar Cells

The photovoltaic properties of solar cell based on the blends of poly[2-methoxy-5-(2-ethylhexoxy-1,4-phenylenevinylene) (MEH-PPV), fullerene (C60), and ZnCdTe-alloyed nanocrystals were investigated. Comparing the spectral response of photocurrent of the MEH-PPV:C60(+ZnCdTe) nanocomposite device with that of the devices based on MEH-PPV:C60and pristine MEH-PPV, one can find that the nanocomposite device exhibits an enhanced photocurrent. In comparing the composite devices with different ZnCdTe:[MEH-PPV + C60] weight ratios of 10 wt% (D1-1), 20 wt% (D1-2), 40 wt% (D1-3), and 70 wt% (D1-4), it was found that the device D1-3exhibits the best performance. The power conversion efficiency (η) is improved doubly compared with that of the MEH-PPV:C60device.