Search

Due to the increasing bacterial resistance to conventional antibiotics, developing safe and effective approaches to combat infections caused by bacteria and biofilms has become an urgent clinical problem. Recently, carbon dots (CDs) have received great attention as a promising alternative to conventional antimicrobial agents due to their excellent antimicrobial efficacy and biocompatibility. Although CDs have been widely used in the field of antibacterial applications, their antibacterial and antibiofilm mechanisms have not been systematically discussed. This review provides a systematic overview on the complicated mechanisms of antibacterial and antibiofilm CDs based on recent development.

The development of artificial intelligence devices in the complementary medicine field is rapid and the surface microbial diversity pollution was found with periodic low-dose ultraviolet radiation (LDUVR). Since artificial intelligence devices do not have enough different types of substrates for microbial communities, it is unclear how the great microbial diversity can emerge and persist, as this clearly defies the competitive exclusion principle of ecology. In this study, the 5 most common genera in the artificial intelligence devices, Escherichia, Pseudomonas, Streptococcus, Staphylococcus and Aeromonas have been sampled without and with periodic LDUVR, respectively. A new hypothesis was put up to clarify the construction and maintenance process of high microbiological diversity in artificial intelligence devices by comparing and evaluating the variations between the dynamic response characteristics of their relative abundances in the two scenarios as follows: the periodic LDUVR can be regarded as an adverse factor with intermediate disturbance, causing stronger microbial stochastic growth responses (SGR) which would inevitably give rise to stronger random variation of the other important processes tightly correlated with SGR, such as intra- and interspecific competition process, and substrates production and consumption process, which could effectively diminish the auto- and cross-correlation of stochastic processes of microbial populations, alleviating the intra- and inter-specific competitions. In artificial intelligence devices with LDUVR, these crucial succession processes can propel the microbial communities to generate and sustain a high species diversity. Finally, thorough Monte Carlo simulations were used to thoroughly confirm the idea. This research can build the theoretical groundwork, offer fresh viewpoints, and suggest potential microbial prevention strategies for the succession of microbial communities in LDUVR.

Cryopreservation is known be an effective method for virus elimination in garlic. However, oxidative damage during the cryopreservation seriously affects the survival of garlic after cryopreservation. Ascorbic acid (AsA) can reduce oxidative damage and improve regrowth following cryopreservation, and its effect may be influenced by the step during which it is added. In this study, AsA was added at the osmoprotection (O) and dehydration (DE) steps of cryopreservation. By observing the dynamic changes in cell viability and reactive oxygen species (ROS) components with different AsA treatments, AsA has been linked to the reduced accumulation of ROS in the shoot tips. Increased gene expression levels of antioxidant enzymes also explained the ROS scavenging effect of AsA. The correlation analysis between cell viability, ROS, membrane lipid peroxidation-related indicators and antioxidant-related indicators showed that membrane lipid peroxidation caused by excess ROS was the main factor affecting cell viability. Ascorbic acid added during dehydration minimized the accumulation of ROS from dehydration to dilution and alleviated the oxidative damage during cryopreservation. Thus, the survival and regrowth of the garlic was significantly improved after cryopreservation. Dehydration was found to be the suitable step for the addition of AsA during garlic cryopreservation. We further evaluated the virus elimination effect under optimal AsA treatment. However, there was no significant difference in virus content in regenerated plants when compared with the control.

Implant-associated infection is a major threat affecting the success of orthopedic surgeries. Although various materials scavenge bacteria by generating reactive oxygen species (ROS), the intrinsic inability of ROS to distinguish bacteria from cells notably limits the therapeutic effects. Here, we found that the arginine carbon dots (Arg-CDs) that were transformed from arginine exhibited supreme antibacterial and osteoinductive activity. We further designed the Schiff base bond between Arg-CDs and aldehyde hyaluronic acid/gelatin methacryloyl (HG) hydrogel to release Arg-CDs in response to the acidic bone injury microenvironment. The free Arg-CDs could selectively kill bacteria by generating excessive ROS. Furthermore, the Arg-CD–loaded HG composite hydrogel showed excellent osteoinductive activity through inducing the M2 polarization of macrophages by up-regulating interleukin-10 ( Il10 ) expression. Together, our findings revealed that transformation of the arginine into zero-dimensional Arg-CDs could endow the material with exceptional antibacterial and osteoinductive activity, favoring the regeneration of infectious bone.

The identification of thermal load/thermal shock of aircrafts during the service is beneficial for collecting information of the service environment and avoiding risks. In the paper, a method based on multivariate information fusion and physics-guided neural network is developed for the inverse problem of thermal load identification of honeycomb sandwich structures. Two thermal feature parameters: temperature gradient and temperature variation rate are used to build the dataset. A 16-layers physics-guided neural network is presented to achieve the predicted results consistent with physical knowledge. In the work, laser irradiation is used as the thermal load, and two laser parameters are to be identified, i.e., spot diameter, power. Simulations and experiments are conducted to verify the effectiveness of the proposed method. The effects of physics-guided loss function and multivariate information fusion are discussed, and it is found that the results based on the proposed method are much better than the results based on the method without physical model. Besides, results based on multivariate information fusion are better than results based on single temperature response. Then, the effects of network models and hyper parameters on the proposed method are also discussed.

Bacterial infection and excessive reactive oxygen species (ROS) remain challenging factors contributing to the delayed healing of chronic wounds. Although various antibacterial and antioxidant hydrogel dressings have been developed to accelerate wound healing, multifunctional hydrogels fabricated by rationally designing and introducing carbonized polymer dots (CPDs) have rarely been reported. Herein, inspired by the mussel biomimetic approach, we synthesized 3,4-dihydroxybenzaldehyde functionalized chitosan (DFC), and then the polymeric precursor was pyrolyzed into CPDs with abundant amino and catechol groups on the surface, which endowed it with a highly positively charged surface that could activate the photothermal effect under near-infrared (NIR) light irradiation. Finally, the nanocomposite hydrogel (PVA@CPDs) was simply constructed by directly mixing polyvinyl alcohol (PVA) with CPDs, utilizing the freeze-thaw cycle method to form a gel, in which, CPDs as a center of polyfunctional nanoparticles drove the formation of PVA microcrystalline crosslinking and endowed the PVA substrate with versatile functionalities. Remarkable and comprehensive improvements in the swelling behavior, mechanical properties and adhesive strength of the hydrogel could be conveniently achieved with the suitable loading of CPDs. The

Local canning compression is imposed on equiatomic NiTi shape memory alloy (SMA) with complete B19′ martensite. A fraction of retained nanocrytalline grains are embedded in the dominant amorphous phase. The compressed NiTi samples are annealed for 2 h at various temperatures, including 300, 450 and 600 °C. Grain size increases with increasing crystallization temperature during heat treatment. Under annealing at 300 °C, nanocrystalline grains are dominant in NiTi SMA, where there exists local amorphous zone. Under annealing at 450 °C, almost complete nanocrystalline can be obtained. Under annealing at 600 °C, grain size increases substantially, but there still exists a small amount of nanocrystalline grains. Under annealing at 300 °C, NiTi SMA exhibits extremely high elastic limit, but its plasticity is poor. Under annealing at 450 °C, NiTi SMA exhibits very high yield stress and it simultaneously keeps high plasticity. Under annealing at 600 °C, NiTi SMA exhibits relatively low yield stress, but its yield stress is still higher than that of as-received NiTi SMA and its plasticity is also high.

Bacterial biofilm infection is perplexing people’s life. Systemic administration of antibiotics usually causes adverse effects and bacterial resistance. How to make antibacterial agents quickly penetrate and eradicate the biofilm without adverse effects is an urgent problem. Here, polyamine-functionalized carbon quantum dots (CQDs), abbreviated as CQD600, CQD1w and CQD2.5w, are synthesized by a simple hydrothermal treatment of citric acid and branched polyethyleneimine (bPEI) with different molecular weight (MW). It is found that the antibacterial activity is promoted with high MW of bPEI, which is due to the protonated amines on the surface of the CQDs. Moreover, in terms of eradicating mature Staphylococcus aureus biofilm, CQD2.5w possesses significantly higher activity than CQD600 and CQD1w because of stronger electrostatic interactions and longer surface coronas. Additionally, the cytotoxicity test exhibits the L929 cells can keep at high survival rates even treated with 500 µg mL−1 CQDs for 3 days. In this study, the surface chemistry related to antibacterial activity and low cytotoxicity give the chance in designing and developing better CQDs for biofilm infection.

Fe66Mn15Si5Cr9Ni5 (wt.%) shape memory alloy (SMA) with γ austenite and e martensite was subjected to mechanical vibrating polishing and consequently its surface suffered from plastic deformation in the case of compressive stress. Almost complete e martensite transformation is found to occur in FeMnSiCrNi sample subjected to mechanical vibrating polishing, where stress-induced martensite transformation plays a predominant role. Stress- induced martensite transformation of FeMnSiCrNi SMA is closely related to the orientation of external stress. The complicated compressive stress which results from the mechanical vibrating polishing contributes to e martensite transformation from γ austenite of FeMnSiCrNi SMA. Mechanical vibrating polishing has a certain influence on the surface texture of e martensite of FeMnSiCrNi SMA, where texture appears in the polished FeMnSiCrNi SMA.

Based on the channel die compression, NiTiFe shape memory alloy (SMA) was subjected to plane strain compression. Mechanically-induced martensite transformation, nanocrystalline and amorphous phase can be observed in the case of large plastic strain. Mechanically-induced martensite transformation is obviously different from the conventional stress-induced martensite transformation. The former generally occurs after dislocation slip, whereas the latter arises prior to dislocation slip. The occurrence of B19’ martensite phase contributes to accommodating subsequent plastic deformation of NiTiFe SMA. Mechanically-induced B19’ martensite is partially stabilized due to the existence of local high stress field and consequently it is unable to be reverted to B2 austenite phase during unloading.

It is very challenging to design nanomaterials with both excellent antibacterial activity and cytocompatibility when facing bacterial infection. Here, inspired by antimicrobial peptides (AMPs), we fabricate carbon quantum dots (CQDs) derived from hydrophobic tryptophan and hydrophilic lysine or arginine (Lys/Trp-CQDs and Arg/Trp-CQDs), which possess amphipathic properties. These CQDs could effectively destroy bacterial membranes without developing resistance, inhibit biofilms formed by

Abscisic acid induced the expression of AsKIN during the recovery period of garlic cryopreservation. AsKIN was identified as a gene involved in cold and osmotic stress resistance. Cryopreservation has been proven to be effective in removing viruses from garlic. However, oxidative damage in cryopreservation has a significant impact on the survival after preservation. Abscisic acid (ABA) has been shown to reduce oxidative stress and promote the survival after cryopreservation. However, it is not clear which genes play important roles in this process. In this study, we added ABA to the dehydration step and analyzed the transcriptomic divergences between the ABA-treated group and the control group in three cryogenic steps (dehydration, unloading and recovery). By short time-series expression miner (STEM) analysis and weighted gene co-expression network analysis (WGCNA), the recovery step was identified as the period of significant changes in gene expression levels in cryopreservation. The addition of ABA promoted the upregulated expression of microtubule-related genes in the recovery step. We further identified AsKIN as a hub gene in the recovery step and verified its function. The results showed that overexpression of AsKIN enhanced the tolerance of Arabidopsis to oxidative stress in cryopreservation, influenced the expression of genes in response to cold and osmotic stress and promoted plant growth after stress. The AsKIN gene is likely to be involved in the plant response to cold stress and osmotic stress. These results reveal the molecular mechanisms of ABA in cryopreservation and elucidate the potential biological functions of the kinesin-14 subfamily.

Bacterial biofilm poses a serious threat to human health, leading to increased and prolonged bacterial infections. How to solve the problem of eliminating biofilms effectively and rapidly while being nontoxic to normal cells is still a challenge. Here, we design a pH-sensitive anti-biofilm nanosystem formed by self-assembly between negatively charged carboxyl groups of poly(ethylene glycol_-COOH-polyethylenimine-2,3-dimethylmaleic anhydride (PPD) and positively charged amines on the surface of carbon dots derived from the ashes of calcined l-lysine powder (CD

We explore the quantum dynamics of nuclear spin relaxation in cold collisions of $^1\Sigma^+$ molecules with structureless atoms in an external magnetic field. To this end, we develop a rigorous coupled-channel methodology, which accounts for rotational and nuclear spin degrees of freedom of $^1\Sigma^+$ molecules, their interaction with an external magnetic field, as well as for anisotropic atom-molecule interactions. We apply the methodology to study collisional relaxation of the nuclear spin sublevels of $^{13}$CO molecules immersed in a cold buffer gas of $^4$He atoms. We find that nuclear spin relaxation in the ground rotational manifold of CO occurs extremely slowly due to the absence of direct couplings between the nuclear spin sublevels. The rates of collisional transitions between the $N=1$ nuclear spin states of CO are generally much higher due to the direct nuclear spin-rotation coupling between the states. These transitions obey selection rules, which depend on the values of space-fixed projections of rotational and nuclear spin angular momenta for the initial and final molecular states. For some initial states, we also observe a strong magnetic field dependence, which can be understood using the first Born approximation. We use our calculated nuclear spin relaxation rates to investigate the thermalization of a single nuclear spin state of CO$(N=0)$ immersed in a cold buffer gas of He. The calculated nuclear spin relaxation times ($T_1\simeq 0.5$ s at $T=1$ K) display a steep temperature dependence decreasing rapidly at elevated temperatures due to the increased population of rotationally excited states, which undergo nuclear spin relaxation at a much faster rate. Thus, long relaxation times of $N=0$ nuclear spin states in cold collisions with buffer gas atoms can only be maintained at sufficiently low temperatures ($kT\ll 2B_e$), where $B_e$ is the rotational constant., Comment: 41 pages, 12 figures

Nanoscale zero-valent iron (nZVI) particles supported on a porous, semi-interpenetrating (semi-IPN), temperature-sensitive composite hydrogel (PNIPAm-PHEMA). nZVI@PNIPAm-PHEMA, was successfully synthesized and characterized by FT-IR, SEM, EDS, XRD and the weighing method. The loading of nZVI was 0.1548 ± 0.0015 g/g and the particle size was 30–100 nm. NZVI was uniformly dispersed on the pore walls inside the PNIPAm-PHEMA. Because of the well-dispersed nZVI, the highly porous structure, and the synergistic effect of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA showed excellent reductive activity and wide pH applicability. 95% of 4-NP in 100 mL of 400 mg/L 4-NP solution with initial pH 3.0–9.0 could be completely reduced into 4-AP by about 0.0548 g of fresh supported nZVI at 18–25 °C under stirring (110 r/min) within 45 min reaction time. A greater than 99% 4-NP degradation ratio was obtained when the initial pH was 5.0–9.0. The reduction of 4-NP by nZVI@PNIPAm-PHEMA was in agreement with the pseudo-first-order kinetics model with Kobs values of 0.0885–0.101 min−1. NZVI@PNIPAm-PHEMA was able to be recycled, and about 85% degradation ratio of 4-NP was obtained after its sixth reuse cycle. According to the temperature sensitivity of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA exhibited very good storage stability, and about 88.9% degradation ratio of 4-NP was obtained after its storage for 30 days. The hybrid reducer was highly efficient for the reduction of 2-NP, 3-NP, 2-chloro-4-nitrophenol and 2-chloro-4-nitrophenol. Our results suggest that PNIPAm-PHEMA could be a good potential carrier, with nZVI@PNIPAm-PHEMA having potential value in the application of reductive degradation of nitrophenol pollutants.

During the reeling process of the reel-lay method, the pipe will be subjected to combined loading of tension and bending. Excessive ovalization of the pipe will affect the structural performance and even lead to structural instability of the pipe. In this paper, a numerical simulation model of the pipe-reeling process is established by finite element tools. The Ramberg–Osgood material model is used to study the ovalization and bending moment of the pipe cross-section during the pipe-reeling process based on the Von Mises plasticity and nonlinear kinematic hardening rules. The results show that the ovalization and bending moment of the pipe section will change significantly during the pipe-reeling process. Subsequently, one set of 6-inch pipe-reeling experimental setups was designed to conduct a full-scale experiment. Compared with the experimental results, the feasibility of the finite element model is verified. Finally, the effects of diameter-to-thickness ratio, the material parameters of the pipe, and the pipe axial tension on the ovalization and bending moment changes are studied. Research shows that each parameter has a certain influence on the pipe of the reeling process, and the diameter-to-thickness ratio of the pipe has the most obvious effect. When the diameter-to-thickness ratio decreases, the bearing capacity for bending moments and the ability to resist ovalization of pipe are enhanced. At the same time, each parameter has a significant impact on the reeling process of the pipeline.

The transient temperature field in the powder bed has a crucial effect on the quality of parts fabricated using Selective Laser Melting (SLM). In this study, a finite element model is established regarding the variance of temperature-dependent thermal properties and transformation latent heat. The temperature distribution and melt pool dimensions of a laser scan track were obtained by varying multiple parameters (layer thickness, laser power and scan speed). The effects of transition of material state and heat source model are also analyzed in this paper. The finite element simulation results show that an increased laser power and/or decreased scan speed results in an elevated maximum temperature of the powder layer and a larger melt pool size. Furthermore, it is found that the maximum temperature is significantly lowered due to the heat diffusion into the previous sintered zone. The heat source model has to be selected properly according to the element size.

Filtration control of drilling fluid plays an important role in the process of wellbore construction and ensures the success of drilling operation. A swellable polymer microsphere (SPM) of methylmethacrylate (MMA), butyl acrylate (BA), and lauryl methacrylate (LMA) was synthesized with suspension polymerization. Its swelling property was characterized by oil adsorption capacity measurement. First, the effect of SPM on the filtration and rheological properties of virgin organic clay dispersion was investigated. Then the filtration and rheological properties of mineral oil-based drilling fluid in the presence of SPM were elucidated under the respective conditions of hot aging temperature, oil to water ratio and density. Furthermore, the filtration control properties between SPM and two traditional filtration loss additives including modified lignite and asphaltic additive was compared. Addition of SPM exhibited obvious influence on the viscosity of oil-based drilling fluid especially at high concentration of 3 w/v%, therefore, a concentration of lower than 1.5 w/v% was recommended. After hot aging at 200 °C, the oil-based drilling fluid containing 1 w/v% SPM exhibited an API filtration loss decrease of 85%, and HTHP filtration loss decrease of 79% in comparison with the base fluid. After hot rolling at 180 °C, the API filtration loss decreased by 2%, 24% and 53%, and the HTHP filtration loss decreased by 42%, 54% and 65% respectively when 1 w/v% asphaltic additive, modified lignite and SPM are in the presence of the base fluid. Besides decreasing the filtration loss volume under high temperatures, incorporation of SPM also improves the filter cake quality of oil-based drilling fluid. SPM is capable of adsorbing considerable base oil and become swellable. The swellable polymer microspheres with favorably deformable and compressible properties can effectively fill the voids of filter cake and reduce the permeability, which leads to low filtration loss and minimization of solids invasion.

A damage-identification method based on flexibility matrix and Teager energy operator is proposed for low-density material–filled sandwich panels with truss core. In the proposed damage index, weight coefficient r is introduced to consider the effect of damages on both high-order and low-order modes. Numerical simulations and experiments are conducted to assess the performance of the proposed method. Effects of Young’s modulus of the filler material on the accuracy of the proposed method are also discussed. Results reveal that the method is reliable and effective for single-damage and multiple-damages identification of filled sandwich panels with truss core, and weight coefficient plays an important role, especially for cases with multiple damages or damages of small extent. Damage identification becomes more difficult as Young’s modulus of the filler increases, and there is a critical value, after which the damage could not be identified by the proposed method.

Research on the cutting-edge nano-fillers for designing dental restorative materials with excellent mechanical property and antibacterial performance is demanding and provoking work. In this study, we fabricated silver-loaded polycation functionalized nanodiamonds (Ag/QNDs) that harbored dual biocidal modes for use as reinforced filler in dental resin. As a result, by reason of homogeneous dispersion and strong bonding with resin matrix, Ag/QNDs-reinforced resin exhibited great improvement of Vickers hardness, flexural strength and modulus as compared with pure resins. Due to the combined bactericidal effect of Ag+ and cationic polymers, Ag/QNDs-containing composites had an excellent antibacterial activity even at a concentration of 1.0 wt% but without significant cytotoxicity. Therefore, development of the Ag/QNDs hybrid is expected to aid in significant improvement of lifetime and quality of dental restorative resin.

Novel bactericidal materials, polycation-based N-halamine functionalized nanodiamonds (PCN-NDs), were fabricated by coating of nanodiamonds (NDs) with quaternarized N-halamine polymers via a facile approach. Chemical modification of the particles was confirmed by FTIR, XPS and TGA. The particle diameters and dispersity of the functionalized NDs were investigated by TEM and DLS measurements. It was found that ND tight core aggregates could be broken into tiny nanoparticles with 40-50 nm through functionalization procedure, which resulted in stable colloidal dispersion solution over one month. The antibacterial tests showed that the PCN-NDs exhibited enhanced antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) compared with their bulk counterparts. The minimum inhibitory concentration values of the as-prepared PCN-NDs are 62.5 μg/mL for both E. coli and S. aureus, even PCN-NDs eliminated nearly 100% of E. coil and S. aureus (107-108 CFU/mg nanoparticles) within 15 min. Furthermore, the as-prepared antimicrobial PCN-NDs exhibited good storage stability and regenerability.

Diabetes is a chronic disease with a high incidence rate. In the context of health care in China, an intelligent monitoring system combining medical care with old-age care has been established based on the service model of combining medical care with old-age care, in view of the reality of diabetes patients, while accurately and effectively identifying the nursing problems of patients with diabetes, a scientific and reasonable individualized nursing plan will be formulated, and the relatively limited nursing resources will be fully utilized, to improve the quality of nursing care for the aged with diabetes mellitus. Based on the model of medical care combined with old-age care, combined with diabetes patients, a comprehensive management model was put forward.

Biocompatible Fe3O4/chitosan (CS)/poly (ethylene glycol) (PEG)/gentamicin (Gent) magnetic nanoparticles, namely Fe3O4@PEG-Gent NPs, have been successfully developed for antibiotic delivery. In which, PEG dicarboxylic acid was used to modify Fe3O4 NPs for good dispersity as well as offer sufficient carboxyl groups as binding sites. And then the free Gent was facilely loaded onto Fe3O4 NPs so as to achieve powerful antibacterial activity via electrostatic interactions. Under acidic condition, the CS and PEG of Fe3O4@PEG-Gent were protonated to introduce the positive charge to NPs surface, thus facilitating the contact with negatively charged bacterial cell membrane. What is more, the stretches of CS chains triggered by acidic pH may prevent the antimicrobial efficiency of Gent from weakening. Compared with the free antibiotic, these nanocomposites presented better antimicrobial efficacy against gram-positive bacteria S. aureus under acidic condition. Intriguingly, the confocal laser scanning macroscopy imaging suggested that the anti-biofilm efficacy of nanocomposites was significantly enhanced in the presence of an external magnetic field. Due to the superparamagnetic performance of Fe3O4 NPs, these nanocomposites were allowed deeper penetration into a mature biofilm of S. aureus by magnetic field, leading to an effective Gent delivery for eradication of biofilm. The ingenious fabrication of the antibiotic delivery system not only efficiently improved the effectiveness and bioavailability of Gent at acidic media, but also provided an innovative platform to treat bacterial biofilms-associated infection by applying extra environmental factors such as magnetic field.

Carbon quantum dots derived from gentamicin sulfate are directly developed by facile calcination at different temperatures. A promising nanomaterial, CQD180, even shows a much superior antibacterial activity compared with the antibiotic counterpart and low drug resistance, by preserving the active structure of the starting materials and providing an additional antibacterial mode arising from the positive charge surface and induced reactive oxygen species simultaneously. Moreover, CQD180 can effectively disrupt mature Staphylococcus aureus biofilm and selectively eliminate bacteria over mammalian cells.

This study aims to analyze the effect of thermomechanical coupling damage caused by laser irradiation on a Carbon Fiber Reinforced Polymer (CFRP) cylindrical shell with axial compression using finite element method (FEM). The quasi-static thermomechanical coupling damage process of a typical CFRP structure was studied intensively. First, a thermomechanical coupling model was established, then the influence of the size of the laser spot, the thickness of the shell and the different exposure location of the laser spot on the critical buckling load (CBL) were investigated. The results show that the value of CBL decreases near quadratically as the shell thickness decreases. The value of CBL decreases nonlinearly with increase of the spot size. The CBL decreases and then increases until the laser reaches the midpoint of cylinder axis as the laser moves along the axial direction of the cylinder; the CBL decreases dramatically as the laser deviates from the axis. DOI: http://dx.doi.org/10.5755/j01.mech.25.2.22340

The application of pit and fissure sealants is a well-established method to prevent and treat early childhood caries. Resin-based sealants with antibacterial properties provide additional benefits for caries prevention in a cariogenic oral environment. The objective of this study was to evaluate the effect of an antibacterial core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) on the properties of a resin-based pit and fissure sealant. A commercialized pit and fissure sealant without fluoride, Concise (3M, ESPE, USA), was used as the parent material and negative control. Experimental antibacterial sealants were formulated by the addition of AgBr/BHPVP nanoparticles at mass fractions of 0.5, 1.0, and 1.5 wt% to the parent material. A fluoride-releasing sealant, Clinpro (3M, ESPE), was used as the positive control. Bacterial colony-forming unit (CFU) counts, metabolic activity tests, field emission-scanning electron microscopy (FE-SEM), and confocal laser scanning microscopy (CLSM) observations were used to evaluate the antibacterial properties of AgBr/BHPVP-modified sealants against Streptococcus mutans before and after five months of aging. The Vickers microhardness, degree of conversion, and microleakage level of the sealants were also investigated. According to the results of CFU counts and metabolic tests, sealants containing AgBr/BHPVP showed better contact-killing bactericidal activity against S. mutans than the two commercial sealants, irrespective of aging conditions (both P 0.05). The AgBr/BHPVP-modified sealants also showed a significant inhibitory effect on the planktonic S. mutans around the cured sealant surfaces. In addition, the Vickers microhardness, degree of conversion, and microleakage level of the parent material were not damaged by modification with AgBr/BHPVP (P 0.05). AgBr/BHPVP-modified pit and fissure sealant with a dual bactericidal mechanism is a promising option for the prevention of pit and fissure caries.

The accurate knowledge of electronic properties is important for creating and manufacturing ultracold molecules. We report here the ab initio quantum chemistry calculations on the properties of alkali-metal-ytterbium AM-Yb (AM = Li, Na, K, Rb, Cs) and alkaline-earth-metal-ytterbium AEM-Yb (AEM = Be, Mg, Ca, Sr, Ba) molecules for their electronic ground state. The potential energy curves (PECs) and permanent dipole moments (PDMs) are calculated on the basis of the multireference configuration interaction (MRCI) level of theory, where the core-valence correlations and scalar relativistic effects are included. The related spectroscopic constants are also determined. The results demonstrate that the dissociation energies and PDMs of AEM-Yb are smaller than those of AM-Yb molecules, and an interesting trend of the dissociation energy has been observed. This work provides favorable information for the experimental study of forming ultracold molecules via photoassociation technique.

Periprosthetic infection represents one of the most devastating complications in orthopedic surgeries. Implants that have both anti-bacterial and bone-forming capability and may function to simultaneously clear infection and repair bone defect, therefore, are highly desirable. In this study, titanium (Ti) substrates were fabricated deposited with different amounts of copper (Cu) using polydopamine (PDA)-based chemical modification technology. In vitro, Ti implants that were treated with PDA and deposited with Cu (Ti-PDA-Cu) showed excellent antibacterial performance against both S. aureus and E. coli compared with pristine Ti. They also markedly promoted adhesion and spreading of MC3T3-E1 cells, implying good biocompatibility of such Ti-PDA-Cu materials. In vivo, results from an animal model of implant-related osteomyelitis clearly demonstrated that Ti-PDA-Cu implants not only effectively inhibited bacterial infection, but also promoted osseointegration at the bone/implant interface. Taken together, these findings show that Ti-PDA-Cu possesses outstanding biocompatibility and antibacterial activity, and are candidate materials for preventing periprosthetic infection.