Novel anionic surfactant-modified chlorhexidine and its potent antimicrobial properties.

Chlorhexidine dodecyl sulfate (CHX-DS) was synthesized and characterized via single-crystal X-ray diffraction (SC-XRD), 1H nuclear magnetic resonance (NMR) spectroscopy, 1H nuclear Overhauser effect spectroscopy (NOESY), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The solid-state structure, comprising a 1 : 2 stoichiometric ratio of chlorhexidine cations [C22H30Cl2N10]2+ to dodecyl sulfate anions [C12H25SO4]-, is the first report of chlorhexidine isolated with a surfactant. CHX-DS exhibits broad-spectrum antibacterial activity and demonstrates superior efficacy for reducing bacteria-generated volatile sulfur compounds (VSCs) as compared to chlorhexidine gluconate (CHG). The minimum inhibitory concentrations (MICs) of CHX-DS were 7.5, 2.5, 2.5, and 10 µM for S. enterica, E. coli, S. aureus, and S. mutans, respectively. Furthermore, MIC assays for E. coli and S. mutans demonstrate that CHX-DS and CHX exhibit a statistically significant efficacy enhancement in 2.5 µM treatment as compared to CHG. CHX-DS was incorporated into SBA-15, a mesoporous silica nanoparticle (MSN) framework, and its release was qualitatively measured via UV-vis in aqueous media, which suggests its potential as an advanced functional material for drug delivery applications.

OTE-SLAM: An Object Tracking Enhanced Visual SLAM System for Dynamic Environments.

With the rapid development of autonomous driving and robotics applications in recent years, visual Simultaneous Localization and Mapping (SLAM) has become a hot research topic. The majority of visual SLAM systems relies on the assumption of scene rigidity, which may not always hold true in real applications. In dynamic environments, SLAM systems, without accounting for dynamic objects, will easily fail to estimate the camera pose. Some existing methods attempt to address this issue by simply excluding the dynamic features lying in moving objects. But this may lead to a shortage of features for tracking. To tackle this problem, we propose OTE-SLAM, an object tracking enhanced visual SLAM system, which not only tracks the camera motion, but also tracks the movement of dynamic objects. Furthermore, we perform joint optimization of both the camera pose and object 3D position, enabling a mutual benefit between visual SLAM and object tracking. The results of experiences demonstrate that the proposed approach improves the accuracy of the SLAM system in challenging dynamic environments. The improvements include a maximum reduction in both absolute trajectory error and relative trajectory error by 22% and 33%, respectively.

Three-dimensional visualization of dentine occlusion based on FIB-SEM tomography.

The occlusion of dentinal tubules has become a rapid and effective method for treating dentin hypersensitivity. Accurate evaluation of dentin occlusion is critical to illustrate the efficacy of oral care products and to optimize dental therapy in the clinics, which is limited by the conventional two-dimensional (2-D) characterization methods. Here, we demonstrate the visualization of the dentin occlusion via three-dimensional (3-D) characterization using a focused ion beam-scanning electron microscopy (FIB-SEM) tomography. Using the "Slice and View" approach, the material used for occluding dentin tubules is imaged with a very high-resolution voxel (10 nm × 10 nm × 20 nm) from 2-D SEM images and then reconstructed into a 3-D volume, which presents the mode of action of toothpaste for treating dentin hypersensitivity. Meanwhile, quantitative analysis of the depth of occlusion is successfully obtained. This work validates the feasibility of FIB-SEM tomography in the analysis of dentin occlusion within the complicated networks of dentine tubules at the nanoscale, and provides a novel approach to facilitate the research and development of oral care products.

Optimization of Escherichia coli shake flask culture medium by artificial neural network / 中国生物制品学杂志

@#Objective To optimize a shake flask culture medium for Escherichia coli(E.coli)with high biomass and viability using artificial neural networks(ANN). Methods Using the proportion of glucose(Glu),yeast extract(YE),yeast peptone(YP),soy peptone(SP)and yeast nitrogen base(YNB)as the mixture component,and the A_(600)(A1)value of cell suspension,wet bacterial weight(G,g/L)of culture and cell viability(A2,A_(460))as the response values,the mixture design was used to screen the mixture components that had a significant effect on the response value. The ANN model was constructed with the test results of mixture design as training and verification data samples. The input variables were mixture components and restricted the upper and lower limits of the mixture components,and the output variables were mixture design response values. The optimized medium formula and reference values were obtained by the constructed ANN. The medium formula was further adjusted by Monte Carlo simulation to obtain the shake flask medium formula of E.coli,which was then verified for 10 times. Results The shake flask culture medium of E.coli was composed of Glu 26 g/L,SP 26 g/L,YNB13 g/L with the total concentration of 65 g/L. The verification results showed that the probability of A1 ≥ 14 was 60%,the probability of G ≥ 77 g/L was 50% and the probability of A2 ≥ 11 was 40%. The mean values of the incubation result data were equivalent to the reference values. Conclusion The shake flask culture medium of E.coli optimized in this study can obtain E.coli with high biomass and bacterial activity.

Understanding the dynamics of fluid-structure interaction with an Air Deflected Microfluidic Chip (ADMC).

A deformable microfluidic system and a fluidic dynamic model have been successfully coupled to understand the dynamic fluid-structure interaction in transient flow, designed to understand the dentine hypersensitivity caused by hydrodynamic theory. The Polydimethylsiloxane thin sidewalls of the microfluidic chip are deformed with air pressure ranging from 50 to 500 mbar to move the liquid meniscus in the central liquid channel. The experiments show that the meniscus sharply increased in the first 10th of second and the increase is nonlinearly proportional to the applied pressure. A theoretical model is developed based on the unsteady Bernoulli equation and can well predict the ending point of the liquid displacement as well as the dynamics process, regardless of the wall thickness. Moreover, an overshooting and oscillation phenomenon is observed by reducing the head loss coefficient by a few orders which could be the key to explain the dentine hypersensitivity caused by the liquid movement in the dentine tubules.

Applications of scanning electron microscopy and focused ion beam milling in dental research.

The abilities of scanning electron microscopy (SEM) and focused ion beam (FIB) milling for obtaining high-resolution images from top surfaces, cross-sectional surfaces, and even in three dimensions, are becoming increasingly important for imaging and analyzing tooth structures such as enamel and dentin. FIB was originally developed for material research in the semiconductor industry. However, use of SEM/FIB has been growing recently in dental research due to the versatility of dual platform instruments that can be used as a milling device to obtain low-artifact cross-sections of samples combined with high-resolution images. The advent of the SEM/FIB system and accessories may offer access to previously inaccessible length scales for characterizing tooth structures for dental research, opening exciting opportunities to address many central questions in dental research. New discoveries and fundamental breakthroughs in understanding are likely to follow. This review covers the applications, key findings, and future direction of SEM/FIB in dental research in morphology imaging, specimen preparation for transmission electron microscopy (TEM) analysis, and three-dimensional volume imaging using SEM/FIB tomography.

Super high-quality SEM/FIB imaging of dentine structures without collagen fiber loss through a metal staining process.

Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) system has become valuable and popular tool for the analysis of biological materials such as dentine structures. According to physiological and anatomical studies, dentine structures are a complicated system containing collagen fibers, nanocrystalline hydroxyapatite, and numerous networks of tubular pores. During a routine FIB milling process, collagen fibers and other organic structures are vaporized, which increases the number of pores on the milled surface of the dentine. This causes the final cross-section to be more porous than the pristine sample. Unfortunately, little attention has been paid to the collagen fiber loss and how to preserve them during a FIB milling process. In this work, we present a novel and simple approach to preserve the organic portions of the dentine structure through metal staining. By using this method, the porosity of the dentine structure after the FIB milling process is significantly reduced similar to the pristine sample. This indicates that the organic portion of the dentine structure is well protected by the metal staining. This approach enables the SEM/FIB system to generate super-high quality SEM images with less ion beam damage; and the SEM images can better reflect the original condition of the dentine structure. Further, serial energy-dispersive X-ray spectroscopy (EDS) mapping of the stained dentine structure is achieved without an additional metal coating; and three-dimensional (3-D) elemental mapping of an occluded dentine is achieved with a significantly reduced data acquisition time.

The integrity of synthetic magnesium silicate in charged compounds.

Magnesium silicate is an inorganic compound used as an ingredient in product formulations for many different purposes. Since its compatibility with other components is critical for product quality and stability, it is essential to characterize the integrity of magnesium silicate in different solutions used for formulations. In this paper, we have determined the magnitude of dissociation of synthetic magnesium silicate in solution with positively charged, neutral, and negatively charged compounds using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS). The EDS results were verified through Monte Carlo simulations of electron-sample interactions. The compounds chosen for this study were positively charged cetylpyridinium chloride (CPC), neutral lauryl glucoside, and negatively charged sodium cocoyl glutamate and sodium cocoyl glycinate since these are common compounds used in personal care and oral care formulations. Negatively charged compounds significantly impacted magnesium silicate dissociation, resulting in physio-chemical separation between magnesium and silicate ions. In contrast, the positively charged compound had a minor effect on dissociation due to ion competition, and the neutral compound did not have such an impact on magnesium silicate dissociation. Further, when the magnesium ions are dissociated from the synthetic magnesium silicate, the morphology is changed accordingly, and the structural integrity of the synthetic magnesium silicate is damaged. The results provide scientific confidence and guidance for product development using synthetic magnesium silicate.

Efficient Electron Transfer from Electron-Sponge Polyoxometalate to Single-Metal Site Metal-Organic Frameworks for Highly Selective Electroreduction of Carbon Dioxide.

In this work, by combining the superiority of polyoxometalates (POMs) and catalytic single-metal site Co of metalloporphyrin, a series of mixed-valence POM-based metal-organic frameworks (MOFs) composites is synthesized by a post-modification method. The electron-transfer property of POM@PCN-222(Co) composite is significantly enhanced owing to the directional electron-transfer from POM to single-metal site Co in PCN-222(Co). In particular, H-POM@PCN-222(Co) gives a high Faradaic efficiency of 96.2% for electroreduction of CO2 into CO and good stability over 10 h. DFT calculations confirm that the directional electron transfer, which accelerates the multi-electron transfer from the electrode to active single-metal site Co, enriches the electron density of the Co center, and ultimately reduces the energy of the rate-determining step, thus increasing the catalytic activity of CO2 reduction reaction (CO2 RR). This work therefore suggests some new insight for the design of efficient electrocatalysts for CO2 RR.

Dual Roles of Polymeric Capping Ligands in the Surface-Protected Etching of Colloidal Silica.

In this work, we reveal the dual roles of polymeric capping ligands in the hollowing of silica nanospheres during their surface-protected etching. We first show that polymeric capping ligands, if they have a stronger interaction with the surface Si-OH groups than water, can reduce the condensation of the silica network, allowing the diffusion of OH- ions through the shell to dissolve the inner silica. Also, the polymeric ligands can passivate the surface silica, making it less likely to be dissolved by OH- ions. The combination of these two roles ensures highly selective etching of the interior of the colloidal silica spheres, making the surface-protected etching a robust process for the synthesis of hollow silica nanoshells. Our insight into the specific roles of the ligands is expected to elucidate the impact of polymeric ligands on the colloidal chemistry of silica, particularly in its condensation and etching behaviors, and offer new opportunities in the design of silica and other oxide-based nanostructures.

Effect of a stannous fluoride toothpaste on dentinal hypersensitivity: In vitro and clinical evaluation.

BACKGROUND: The authors conducted an in vitro and a clinical study to assess the effect of a toothpaste containing stannous fluoride to occlude dentin tubules and reduce dentinal hypersensitivity. METHODS: For the in vitro study, the authors treated the surface of human dentin specimens with test or control toothpaste slurries and then evaluated them by using various spectroscopic techniques. For the clinical study, male and female participants who met the inclusion criteria brushed their teeth twice daily for 1 minute with test or control toothpaste. The authors assessed dentinal hypersensitivity by using tactile and air blast stimuli at baseline and after 4 and 8 weeks. All statistical tests of hypotheses were 2 sided, with a significance level of α set at .05. RESULTS: Results from in vitro studies showed that the test toothpaste effectively occluded the dentinal tubules with a deposit consisting of tin, zinc, phosphate, and silicon. The test and control toothpastes occluded the tubules 82% and 35%, respectively. Clinically, at the 4- and 8-week examinations, the test toothpaste provided statistically significant (P < .001) improvements in tactile dentinal hypersensitivity scores of 27.8% and 42.0% and in air blast hypersensitivity scores of 21.4% and 32.3%, respectively, relative to the control toothpaste. CONCLUSIONS: The in vitro results indicate the toothpaste containing 0.454% stannous fluoride effectively coated dentin surfaces and occluded patent dentin tubules. Compared with the control toothpaste, the test toothpaste provided a significant reduction in dentinal hypersensitivity after 8 weeks of product use. PRACTICAL IMPLICATIONS: A multi-benefit option for patients with dentinal hypersensitivity.

Adaptive ISAR Imaging of Maneuvering Targets Based on a Modified Fourier Transform.

Focusing on the inverse synthetic aperture radar (ISAR) imaging of maneuvering targets, this paper presents a new imaging method which works well when the target's maneuvering is not too severe. After translational motion compensation, we describe the equivalent rotation of maneuvering targets by two variables-the relative chirp rate of the linear frequency modulated (LFM) signal and the Doppler focus shift. The first variable indicates the target's motion status, and the second one represents the possible residual error of the translational motion compensation. With them, a modified Fourier transform matrix is constructed and then used for cross-range compression. Consequently, the imaging of maneuvering is converted into a two-dimensional parameter optimization problem in which a stable and clear ISAR image is guaranteed. A gradient descent optimization scheme is employed to obtain the accurate relative chirp rate and Doppler focus shift. Moreover, we designed an efficient and robust initialization process for the gradient descent method, thus, the well-focused ISAR images of maneuvering targets can be achieved adaptively. Human intervention is not needed, and it is quite convenient for practical ISAR imaging systems. Compared to precedent imaging methods, the new method achieves better imaging quality under reasonable computational cost. Simulation results are provided to validate the effectiveness and advantages of the proposed method.

Energy scavenging based on a single-crystal PMN-PT nanobelt.

Self-powered nanodevices scavenging mechanical energy require piezoelectric nanostructures with high piezoelectric coefficients. Here we report the fabrication of a single-crystal (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMN-PT) nanobelt with a superior piezoelectric constant (d33 = ~550 pm/V), which is approximately ~150%, 430%, and 2100% of the largest reported values for previous PMN-PT, PZT and ZnO nanostructures, respectively. The high d33 of the single-crystalline PMN-PT nanobelt results from the precise orientation control during its fabrication. As a demonstration of its application in energy scavenging, a piezoelectric nanogenerator (PNG) is built on the single PMN-PT nanobelt, generating a maximum output voltage of ~1.2 V. This value is ~4 times higher than that of a single-CdTe PNG, ~13 times higher than that of a single-ZnSnO3 PNG, and ~26 times higher than that of a single-ZnO PNG. The profoundly increased output voltage of a lateral PNG built on a single PMN-PT nanobelt demonstrates the potential application of PMN-PT nanostructures in energy harvesting, thus enriching the material choices for PNGs.

Biotemplated synthesis of PZT nanowires.

Piezoelectric nanowires are an important class of smart materials for next-generation applications including energy harvesting, robotic actuation, and bioMEMS. Lead zirconate titanate (PZT), in particular, has attracted significant attention, owing to its superior electromechanical conversion performance. Yet, the ability to synthesize crystalline PZT nanowires with well-controlled properties remains a challenge. Applications of common nanosynthesis methods to PZT are hampered by issues such as slow kinetics, lack of suitable catalysts, and harsh reaction conditions. Here we report a versatile biomimetic method, in which biotemplates are used to define PZT nanostructures, allowing for rational control over composition and crystallinity. Specifically, stoichiometric PZT nanowires were synthesized using both polysaccharide (alginate) and bacteriophage templates. The wires possessed measured piezoelectric constants of up to 132 pm/V after poling, among the highest reported for PZT nanomaterials. Further, integrated devices can generate up to 0.820 µW/cm(2) of power. These results suggest that biotemplated piezoelectric nanowires are attractive candidates for stimuli-responsive nanosensors, adaptive nanoactuators, and nanoscale energy harvesters.

Flexible piezoelectric PMN-PT nanowire-based nanocomposite and device.

Piezoelectric nanocomposites represent a unique class of materials that synergize the advantageous features of polymers and piezoelectric nanostructures and have attracted extensive attention for the applications of energy harvesting and self-powered sensing recently. Currently, most of the piezoelectric nanocomposites were synthesized using piezoelectric nanostructures with relatively low piezoelectric constants, resulting in lower output currents and lower output voltages. Here, we report a synthesis of piezoelectric (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) nanowire-based nanocomposite with significantly improved performances for energy harvesting and self-powered sensing. With the high piezoelectric constant (d33) and the unique hierarchical structure of the PMN-PT nanowires, the PMN-PT nanowire-based nanocomposite demonstrated an output voltage up to 7.8 V and an output current up to 2.29 µA (current density of 4.58 µA/cm(2)); this output voltage is more than double that of other reported piezoelectric nanocomposites, and the output current is at least 6 times greater. The PMN-PT nanowire-based nanocomposite also showed a linear relationship of output voltage versus strain with a high sensitivity. The enhanced performance and the flexibility of the PMN-PT nanowire-based nanocomposite make it a promising building block for energy harvesting and self-powered sensing applications.

In situ mechanical and electrical characterization of individual TiO2 nanofibers using a nanomanipulator system.

Young's modulus and electrical resistivity of individual titanium dioxide (TiO(2)) nanofibers were characterized using a nanomanipulator system installed in a focused ion beam-scanning electron microscope (FIB-SEM) dual-beam Scanning Electron Microscope system. Young's modulus of individual nanofibers was deduced from the analysis of their in situ resonance behavior in response to an oscillating electric field. The electrical behavior of a single nanofiber was also analyzed by a two-point method probed by a nanomanipulator. These results will contribute to the design of devices based on single TiO(2) nanofibers, as well as devices based on nanofiber networks. The methods presented here can also be applied to characterize other one-dimensional nanostructures.

PMN-PT nanowires with a very high piezoelectric constant.

A profound way to increase the output voltage (or power) of the piezoelectric nanogenerators is to utilize a material with higher piezoelectric constants. Here we report the synthesis of novel piezoelectric 0.72Pb(Mg(1/3)Nb(2/3))O(3)-0.28PbTiO(3) (PMN-PT) nanowires using a hydrothermal process. The unpoled single-crystal PMN-PT nanowires show a piezoelectric constant (d(33)) up to 381 pm/V, with an average value of 373 ± 5 pm/V. This is about 15 times higher than the maximum reported value of 1-D ZnO nanostructures and 3 times higher than the largest reported value of 1-D PZT nanostructures. These PMN-PT nanostructures are of good potential being used as the fundamental building block for higher power nanogenerators, high sensitivity nanosensors, and large strain nanoactuators.

Influence of Ca(2+) and Suwannee River Humic Acid on aggregation of silicon nanoparticles in aqueous media.

Silicon nanoparticles (NPs) have potential applications in many fields including microelectronics, biomedical imaging, and most recently energetics. Even though silicon NPs are thought to be harmless, their full impact on the environment and human health needs further investigation due to their potential increased use and recent toxicity data. Various techniques were used to characterize silicon NPs that are being considered for use in energetics. These techniques included dynamic light scattering (DLS), electron microscopy (EM), X-ray diffraction (XRD) and atomic force microscopy (AFM). Experiments were also conducted on the early stage aggregation kinetics of silicon NPs in the presence of Ca(2+) and Suwannee River Humic Acid (SRHA). The addition of SRHA in the presence of Ca(2+) resulted in increased attachment efficiencies and decreased critical coagulation concentration (from 0.4 to 0.1M). The enhanced aggregation was attributed to bridging generated by SRHA aggregates as evidenced by selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS). SAED verified the bridging to be amorphous phase comprised of humic substances rather than artifacts of silicon crystallites. Element distribution analyses were also used in the delineation of the silicon NP aggregation mechanisms in the absence and presence of SRHA.

1.6 V nanogenerator for mechanical energy harvesting using PZT nanofibers.

Energy harvesting technologies that are engineered to miniature sizes, while still increasing the power delivered to wireless electronics, (1, 2) portable devices, stretchable electronics, (3) and implantable biosensors, (4, 5) are strongly desired. Piezoelectric nanowire- and nanofiber-based generators have potential uses for powering such devices through a conversion of mechanical energy into electrical energy. (6) However, the piezoelectric voltage constant of the semiconductor piezoelectric nanowires in the recently reported piezoelectric nanogenerators (7-12) is lower than that of lead zirconate titanate (PZT) nanomaterials. Here we report a piezoelectric nanogenerator based on PZT nanofibers. The PZT nanofibers, with a diameter and length of approximately 60 nm and 500 microm, were aligned on interdigitated electrodes of platinum fine wires and packaged using a soft polymer on a silicon substrate. The measured output voltage and power under periodic stress application to the soft polymer was 1.63 V and 0.03 microW, respectively.