Zr/(Sc+Zr)微合金化对Al-Mg合金在热压缩变形中动态再结晶、位错密度和热加工性能的影响

采用热压缩试验和电子显微分析方法研究Al-6.00Mg、Al-6.00Mg-0.10Zr和Al-6.00Mg-0.25Sc-0.10Zr (质量分数,%)合金的变形行为和显微组织特征。结果表明,在最大加工效率条件(673 K,0.01 s^(-1))下变形时,Al-6.00Mg、Al-6.00Mg-0.10Zr和Al-6.00Mg-0.25Sc-0.10Zr合金的位错密度分别为2.68×10^(16)、8.93×10^(16)和6.1×10^(17)m^(-2);其动态再结晶分数分别为19.8%、15.0%和12.7%。中心点平均取向差(KAM)分析表明,通过添加Zr或Sc+Zr,Al-Mg合金晶界附近的位错密度增加。此外,基于动态材料模型(DMM)建立的热加工图表明,添加Zr或Sc+Zr能减小Al-Mg合金的低温不稳定域的范围,但会增大高温和高应变不稳定域的范围。实验结果进一步证明,在变形条件下,仅Al-6.00Mg-0.25Sc-0.10Zr合金在773 K和1 s^(-1)时开裂。

Theoretical Study of Dibenzothiophene Based Electron Transport Materials

Density functional methods have been used for the calculation of electronic structures, electronic transitions, vertical electron affinities and intermolecular reorganization energies for tri-aryl substituted dibenzothiophenes. These model compounds were then compared to the predicted values for dibenzo[b,d]thiophen-2-yltriphenylsilane (DBTSI 2) and to dibenzo[b,d]thiophene-2,8-diylbis(diphenylphosphine oxide) (PO15), known electron transport molecules. The results indicate that these model compounds can be used in a blue OLED system.

Al_(3)(Sc_(1-x)Zr_(x))纳米粒子对搅拌摩擦焊Al-Mg-Mn合金显微组织和力学性能的影响

通过拉伸测试和显微分析方法研究搅拌摩擦焊Al-5.50Mg-0.45Mn和Al-5.50Mg-0.45Mn-0.25Sc-0.10Zr(质量分数,%)合金的显微组织和力学性能。结果表明,Al-Mg-Mn接头的屈服强度、抗拉强度和伸长率分别为(191±3)MPa、(315±1)MPa和(4.8±1.9)%,Al-Mg-Mn-Sc-Zr接头的分别为(288±5)MPa、(391±2)MPa和(3.4±1.0)%。相比Al-Mg-Mn接头,Al-Mg-Mn-Sc-Zr接头晶粒更细小、平均取向差角更低、小角度晶界百分数更高。两种接头的断裂位置均位于焊核区(WNZ),在该“最薄弱微区”内,Al_(3)(Sc_(1-x)Zr_(x))纳米粒子的平均尺寸为(9.92±2.69)nm,可提供有效奥罗万和晶界强化,使Al-Mg-Mn接头的屈服强度提高97 MPa。

A comprehensive analysis of the role of molecular docking in the development of anticancer agents against the cell cycle CDK enzyme

Cancer is considered one of the most lethal diseases responsible for causing deaths worldwide.Although there have been many breakthroughs in anticancer development,cancer remains the major cause of death globally.In this regard,targeting cancer-causing enzymes is one of the efficient therapeutic strategies.Biological functions like cell cycle,transcription,metabolism,apoptosis,and other depend primarily on cyclin-dependent kinases(CDKs).These enzymes help in the replication of DNA in the normal cell cycle process,and deregulation in the functioning of any CDK can cause abnormal cell growth,which leads to cancer.This review is focused on anticancer drug discovery against cell cycle CDK enzyme using an in silico technique,i.e.,molecular docking studies.Molecular docking helps in deciphering the key interactions formed within the inhibitor and the respective enzyme.This concise study provides an overview of the most current in silico research advancements made in the field of anticancer drug discovery.The findings presented in the current review article can help in understanding the nature of inhibitor-target interactions and provide information on the structural and molecular prerequisites for the inhibition of cell cycle CDKs.

Preparation of High Percentage α-Calcium Sulfate Hemihydrate via a Hydrothermal Method

α-calcium sulfate hemihydrate (α-HH) is known to be suitable for application as bone void filler. High percentage of α-HH is obviously needed for medical applications, especially for implantation. Three commercially available calcium sulfate dihydrates (DH, CaSO4·2H2O) with different sizes and surface morphologies were used as starting materials to synthesize high percentage α-HH via a hydrothermal method. The median particle sizes of the three types of DH were 946.7 μm, 162.4 μm and 62.4 μm, respectively. They were named as DH-L, DH-M and DH-S in this paper. The particle size distribution, morphology and phase composition of the raw materials were evaluated before synthesis. SEM results revealed that DH-L consisted of irregular large particles, while DH-M and DH-S were composed of plate-like particles with some small ones. High percentage HH can be obtained with proper synthesis parameters by hydrothermal method, specifically, 105 °C/90 min for DH-L (achieving 98.8% HH), 105°C/30 min for DH-M (achieving 96.7% HH) and 100°C/45 min for DH-S (achieving 98.4% HH). All the synthesized HH were hexagonal columns, demonstrating that they were α-phase HH. The particle size and morphology of starting material (DH) have significant influences on not only the rate of phase transition but also the morphology of the synthesized α-HH. Calcium sulfate dihydrate cements were prepared by the synthesized α-HH. The highest compressive strength of calcium sulfate dihydrate cement was 17.2 MPa. The results show that the preparation of high percentage α-HH is feasible via a hydrothermal method and the process can be further scaled up to industrial scale production.

Substituted Molecular <i>p</i>-Dopants: A Theoretical Study

Conductivity dopants with processing properties suitable for industrial applications are of importance to the organic electronics field. However, the number of commercially available organic molecular dopants is limited. The electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (F4-TCNQ) is the most utilized P-dopant;however, it has high volatility and a poor sticking coefficient, which makes it difficult to control doping levels and prevent vacuum system contamination. A design concept for P-type molecular dopants based on the TCNQ core which are substituted to improve processing properties without sacrificing the electronic properties necessary is presented. The correlation between the lowest unoccupied molecular orbital (LUMO) energy and the position of substitution as well as the choice of linker is evaluated. The position of substitution as well as the choice of linker has a significant effect on the electronic properties. However, the geometry of the substituted molecules was not significantly distorted from that of the parent F4-TCNQ, and the electron density was delocalized on the TCNQ core. We also put forward four possible molecular dopants with suitable energy levels.

Bismuth (III) Chloride Catalyzed Multicomponent Synthesis of Substituted Hexahydroimidazo[1, 2-<i>a</i>]Pyridines

The synthesis of nitrogen containing heterocycles is of particular interest in the pharmaceutical industry due to the range of biological activities exhibited by such compounds. Their synthesis using multicomponent reactions saves steps and minimizes waste generation. The bismuth (III) chloride multicomponent synthesis of a series of hexahydroimidazo[1, 2-a]pyridines is reported. Bismuth (III) compounds are especially attractive from a green chemistry perspective because they are remarkably nontoxic, non-corrosive and relatively inexpensive. The reported method avoids chromatography and an aqueous waste stream to afford the products in a very mass efficient manner.

Effect of Calcium and Strontium on Mesoporous Titania Coatings for Implant Applications

Increasing interest in the role of ions such as calcium and strontium in bone formation has called for the investigation of multifunctional ion-doped implant coatings. Mesoporous titania coatings incorporating calcium or strontium enabled a unique pore morphology and potential for drug delivery. Coatings were produced on titanium by an evaporation induced self-assembly method with the addition of calcium or strontium to the sol causing a shift in morphology from a hexagonally-packed to a worm-like porous network. Pore sizes ranged from 3.8 - 5 nm and coatings exhibited high surface areas between 181 - 215.5 m2/g, as measured by N2 adsorption-desorption. Coatings were loaded with 1 mg/ml Cephalothin, and showed sustained release of the antibiotic over one week in vitro. Cell studies confirmed that the ion addition had no toxic effect on human-like osteoblastic SaOS-2 cells. The results of this study suggest the potential for mesoporous coatings with calcium or strontium incorporation for direct bone-interfacing and combined drug delivery implant applications.

Synthesis, Characterization and Crystal Structures of Zwitterionic Triazolato Complexes by Reaction of a Ruthenium Azido Complex with Excess Ethyl Propiolate

The synthesis and structures of two novel zwitterionic ruthenium triazolato complexes are reported. The treatment of the ruthenium azido complex [Ru]-N3 (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with an excess of ethyl propiolate in CHCl3 or CH2Cl2 under ambient conditions for 15 days results in the formation of a mixture of the Z- and E-forms of N(1)-bound ruthenium 3-ethylacryl-4-carboxylate-3H-1,2,3-triazolato complexes [Ru]N3(CH=CHCO2Et)C2H(CO2) (Z-3) and (E-3) in a ratio of ca. 5:2. The structures of E-3 and Z-3 were confirmed by single-crystal X-ray diffraction analysis and fully characterized by 1H, 31P, 13C NMR and IR spectroscopy, mass spectrometry, and elemental analysis. The negatively charged carboxylate moieties of the zwitterionic ruthenium triazolato complexes Z-3 and Z-3 are highly nucleophilic and reactive toward a variety of electrophiles, making Z-3 and Z-3 potential starting materials for the development of biologically active 1,2,3-triazole derivatives.

Controlling Osteogenic Differentiation through Nanoporous Alumina

Nanotopographical features are found to have significant effects on bone behavior. In the present study, nanoporous aluminas with different pore sizes (20, 100 and 200 nm in diameter), were evaluated for their osteoinductive and drug eluting properties. W20-17 marrow stromal cells were seeded on nanoporous alumina with and without the addition of BMP-2. Although cell proliferation was not affected by pore size, osteogenic differentiation was 200 nm as compared to 20 and 100 nm pores induced higher alkaline phosphatase activity (ALP) and osteocalcin expression levels, thus indicating osteoblastic differentiation. Cell morphology revealed that cells cultured on 20 nm pores adopted a rounded shape, while larger pores (200 nm) elicited an elongated morphology. Furthermore, ALP expression levels were consistently higher on BMP-2 loaded nanoporous alumina surfaces compared to unloaded surfaces, indicating that not only is nanoporous alumina osteoinductive, but also has the potential to be used as a drug eluting bone-implant coating.

Strontium and Silicon Co-Doped Apatite Coating: Preparation and Function as Vehicles for Ion Delivery

New methods to improve the bone response to metallic implants are still emerging, ranging from surface modifications of the metal to coatings and drug delivery. One further development of coatings on implants is to incorporate bioactive ions in order to stimulate the bone response without the need of drug delivery. The aim of the current study is to prepare apatite coatings containing Sr and Si using a solution method, for the purpose of further optimising the bone response to metal implants. Titanium substrates were activated to induce the formation of coatings in modified PBS solutions. Soaking in PBS solutions with different concentrations of strontium and silicate at 37℃ or 60℃ produced coatings with different morphologies, thicknesses and compositions. Ion release experiments showed simultaneous release of Sr and Si from the coatings both in PBS and Tris-HCl. Analysis of the results using the Korsmeyer-Peppas model indicate that the release of ions from the coatings was a combination of Fickian diffusion and degradation of the coatings. This study shows that it is possible to coat Ti substrates with modified apatite with ion release functionality and thereby increase the possibilities for a tailored bone response in vivo.

The Effect of Si-Doping on the Release of Antibiotic from Hydroxyapatite Coatings

Herein, we show that incorporation of ions during biomimetic coating deposition may be utilized to tailor the drug loading capacity of hydroxyapatite (HA) coatings. Pure biomimetic HA (HA-B) and Si-doped equivalents (SiHA-B) where deposited by a biomimetic process onto titanium dioxide covered titanium substrates. The antibiotic Cephalothin was incorporated into the coatings by adsorptive loading and the release was studied in-vitro. SiHA-B coatings exhibited superior drug incorporation capacity compared to pure HA-B coatings, resulting in a drug release profile dominated by an initial 10 min burst effect while a more prolonged 10 hour release was observed from HA-B coatings. The results emphasize the possibility to impact the drug release kinetics from implant coatings by selective doping elements and the use of thin, biomimetic HA-coatings as drug delivery vehicles. Functionalizing metal implants with SiHA-B coatings presents an interesting strategy towards creating synergetic effects through ion- and antibiotic release and, hence, contributing both towards preventing post-surgical infections while at the same time enhancing the bone-bonding ability.

Changes of Surface Composition and Morphology after Incorporation of Ions into Biomimetic Apatite Coating

Fabrication of trace elements incorporated apatite coating could combine the ions’ pharmaceutical effect into the materials. In this study, strontium, silicon, and fluoride ions have been incorporated into apatite coatings through a biomineralization method, which mimics an in vitro mineralization process. The surface composition is tested with X-ray diffraction and X-ray photoelectron spectroscopy, and the surface morphology is characterized with scanning electron microscopy. Compared with pure hydroxyapatite coating, the strontium, silicon, and fluoride substituted apatite coatings show different morphology as spherical, needle-like, and nano-flake-like, individually. The crystal size of these biomimetic hydroxyapatite coatings decreased after ion substitution. The results of the analysis of surface composition present the ion substitutions are increased with the increasing of ion concentrations in the soaking solution. That means the ion incorporation into the apatite structure based on the biomineralization method could not only vary the ion content in but also change the morphology of the apatite coatings. Herein, the role of ion substitution is considered from the point of view of materials science at the micro structural and surface chemistry levels.

Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal In-Vivo

The early fixation of bone screws after surgical implantation still remains a challenge in the field of traumatology. Whilst hydroxyapatite (HA) coatings are known to enhance the fixation of implants;their removal at a later time-point may be problematic. An HA coating has been developed to demonstrate that both implant fixation and safe removal are feasible in the same design. Accordingly the aim of this study was to compare the In-Vivo performance of thin biomimetic HA coated titanium screws to uncoated counterparts used as control after bilateral implantation in the femoral condyle of 36 New Zealand White Rabbits. The screws were analysed macroscopically, by histology, micro-CT and biomechanically at both two and six weeks post-implantation. The HA coated screws demonstrated excellent biocompatibility. At two weeks the HA coated screws demonstrated a significant increase in removal torque values as well as a strong trend towards higher pull-out forces. In addition histology confirmed a higher degree of osseointegration and direct bone to implant contact. At six weeks no difference in pull-out force and removal torque could be detected. SEM images confirmed the absence of any residual HA coating indicating a fast coating degradation In-Vivo. The low level of removal torque after full osseointegration at 6 weeks supports the feasibility of safe and easy removal of the implant. The HA coating under study appears to offer a unique characteristic of enhanced fixation with a minimal increase in removal torque after full osseointegration. This may be of value in clinical applications where it is necessary to assure both screw fixation and later removal.

Bone without borders-Monetite-based calcium phosphate guides bone formation beyond the skeletal envelope

Calcium phosphates(CaP)represent an important class of osteoconductive and osteoinductive biomaterials.As proof-of-concept,we show how a multi-component CaP formulation(monetite,beta-tricalcium phosphate,and calcium pyrophosphate)guides osteogenesis beyond the physiological envelope.In a sheep model,hollow dome-shaped constructs were placed directly over the occipital bone.At 12 months,large amounts of bone(~75%)occupy the hollow space with strong evidence of ongoing remodelling.Features of both compact bone(osteonal/osteon-like arrangements)and spongy bone(trabeculae separated by marrow cavities)reveal insights into function/need-driven microstructural adaptation.Pores within the CaP also contain both woven bone and vascularised lamellar bone.Osteoclasts actively contribute to CaP degradation/removal.Of the constituent phases,only calcium pyrophosphate persists within osseous(cutting cones)and non-osseous(macrophages)sites.From a translational perspective,this multi-component CaP opens up exciting new avenues for osteotomy-free and minimally-invasive repair of large bone defects and augmentation of the dental alveolar ridge.

Low-temperature and flexible strategy to in-situ fabricate ZrSiO_(4)-based ceramic composites via doping and tuning solid-state reaction

Synthetic zircon(ZrSiO_(4))ceramics are typically fabricated at elevated temperatures(over 1500℃),which would lead to high manufacturing cost.Meanwhile,reports about preparing ZrSiO_(4)-based ceramic composites via controlling the solid-state reaction between zirconia(ZrO_(2))and silica(SiO_(2))are limited.In this work,we proposed a low-temperature strategy to flexibly design and fabricate ZrSiO_(4)-based ceramic composites via doping and tuning the solid-state reaction.Two ceramic composites and ZrSiO_(4) ceramics were in-situ prepared by reactive fast hot pressing(FHP)at approximately 1250℃ based on the proposed strategy,i.e.,a ZrSiO_(4)-SiO_(2) dual-phase composite with bicontinuous interpenetrating and hierarchical microstructures,a ZrSiO_(4)-ZrO_(2) dual-phase composite with a microstructure of ZrO_(2) submicron-and nano-particles embedded in a micron ZrSiO_(4) matrix,and ZrSiO_(4) ceramics with a small amount of residual ZrO_(2) nanoparticles.The results showed that the phase compositions,microstructure configurations,mechanical properties,and wear resistance of the materials can be flexibly regulated by the proposed strategy.Hence,ZrSiO_(4)-based ceramic composites with different properties can be easily fabricated based on different application scenarios.These findings would offer useful guidance for researchers to flexibly fabricate ZrSiO_(4)-based ceramic composites at low temperatures and tailor their microstructures and properties through doping and tuning the solid-state reaction.

Microscale study of frictional properties of graphene in ultra high vacuum

We report on the frictional properties of epitaxial graphene on SiC in ultra high vacuum.Measurements have been performed using a microtribometer in the load regime of 0.5 to 1 mN.We observed that a ruby sphere sliding against graphene results in very low friction coefficients ranging from 0.02 to 0.05.The friction and also the stability of the graphene layer is higher than that under similar conditions in ambient conditions.The friction shows a load dependence.Finally it was found that graphene masks the frictional anisotropy which was observed on the SiC surface.

Injectable reactive oxygen and nitrogen species-controlling hydrogels for tissue regeneration:current status and future perspectives

The dual role of reactive oxygen and nitrogen species(RONS)in physiological and pathological processes in biological systems has been widely reported.It has been recently suggested that the regulation of RONS levels under physiological and pathological conditions is a potential therapy to promote health and treat diseases,respectively.Injectable hydrogels have been emerging as promising biomaterials for RONS-related biomedical applications owing to their excellent biocompatibility,three-dimensional and extracellular matrix-mimicking structures,tunable properties and easy functionalization.These hydrogels have been developed as advanced injectable platforms for locally generating or scavenging RONS,depending on the specific conditions of the target disease.In this review article,the design principles and mechanism by which RONS are generated/scavenged from hydrogels are outlined alongside a discussion of their in vitro and in vivo evaluations.Additionally,we highlight the advantages and recent developments of these injectable RONS-controlling hydrogels for regenerativemedicines and tissue engineering applications.