Decontamination-Induced Modification of Bioactivity in Essential Oil-Based Plasma Polymer Coatings

Plasma polymer coatings fabricated from Melaleuca alternifolia essential oil and its derivatives have been previously shown to reduce the extent of microbial adhesion on titanium, polymers, and other implantable materials used in dentistry. Previous studies have shown these coatings to maintain their performance under standard operating conditions; however, when used in e.g., a dental implant, these coatings may inadvertently become subject to in situ cleaning treatments, such as those using an atmospheric pressure plasma jet, a promising tool for the effective in situ removal of biofilms from tissues and implant surfaces. Here, we investigated the effect of such an exposure on the antimicrobial performance of the Melaleuca alternifolia polymer coating. It was found that direct exposure of the polymer coating surface to the jet for periods less than 60 s was sufficient to induce changes in its surface chemistry and topography, affecting its ability to retard subsequent microbial attachment. The exact effect of the jet exposure depended on the chemistry of the polymer coating, the length of plasma treatment, cell type, and incubation conditions. The change in the antimicrobial activity for polymer coatings fabricated at powers of 20–30 W was not statistically significant due to their limited baseline bioactivity. Interestingly, the bioactivity of polymer coatings fabricated at 10 and 15 W against Staphylococcus aureus cells was temporarily improved after the treatment, which could be attributed to the generation of loosely attached bioactive fragments on the treated surface, resulting in an increase in the dose of the bioactive agents being eluted by the surface. Attachment and proliferation of Pseudomonas aeruginosa cells and mixed cultures were less affected by changes in the bioactivity profile of the surface. The sensitivity of the cells to the change imparted by the jet treatment was also found to be dependent on their origin culture, with mature biofilm-derived P. aeruginosa bacterial cells showing a greater ability to colonize the surface when compared to its planktonic broth-grown counterpart. The presence of plasma-generated reactive oxygen and nitrogen species in the culture media was also found to enhance the bioactivity of polymer coatings fabricated at power levels of 10 and 15 W, due to a synergistic effect arising from simultaneous exposure of cells to reactive oxygen and nitrogen species (RONS) and eluted bioactive fragments. These results suggest that it is important to consider the possible implications of inadvertent changes in the properties and performance of plasma polymer coatings as a result of exposure to in situ decontamination, to both prevent suboptimal performance and to exploit possible synergies that may arise for some polymer coating-surface treatment combinations.     

关于K个复相关矩阵相等的检验

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High‐spatial‐resolution mapping of superhydrophobic cicada wing surface chemistry using infrared microspectroscopy and infrared imaging at two synchrotron beamlines

The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada (Psaltoda claripennis) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS‐IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin‐Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self‐cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher‐spatial‐resolution distribution images in a shorter time than was achievable at the AS‐IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS‐IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for example, industry applications.     

Sub-wavelength surface structures on silicon irradiated by femtosecond laser pulses at 1300 and 2100 nm wavelengths

We present periodic ripples and arrays of protrusions formed on the surface of silicon after irradiation by low-fluence linearly polarized femtosecond laser pulses. Laser-induced periodic surface structures (LIPSS) are observed for irradiation at center wavelengths of 800, ∼ 1300, and ∼ 2100 nm, with the structure periods somewhat less than the incident wavelengths in air. Additionally, we observe structures with spatial periods substantially less than the incident laser wavelengths. These sub-wavelength periodic structures form only when the photon energy is less than the silicon bandgap energy. We discuss a number of factors which may contribute to the generation of this surface morphology.     

Ripple formation during deep hole drilling in copper with ultrashort laser pulses

Cross sections of deep holes produced by ultrashort laser pulses and showing a variety of microstructural formations are presented. After tens of thousands of 800 nm wavelength pulses, the walls of the holes show distinct ripples with a period of ∼300 nm. It is demonstrated that these ripples are the result of light interference effects. Indeed, the ripples are perpendicular to the electric field of the laser beam and their spacing scales with the laser wavelength. Additional fine ripples with spacing of ∼75 nm were also observed. PACS 62.20.Mk; 62.25.+g; 79.20.Ds     

Thermal solid state synthesis of coordination complexes from hydrogen bonded precursors

Thermal dehydrochlorination of crystalline 4-picolinium salts of [PtCl4]2- and [PdCl4]2- leads to formation of trans-[MCl2(4-picoline)2](M = Pt, Pd).     

Narrowing of the balance function with centrality in Au+Au collisions at the square root of SNN = 130 GeV

The balance function is a new observable based on the principle that charge is locally conserved when particles are pair produced. Balance functions have been measured for charged particle pairs and identified charged pion pairs in Au+Au collisions at the square root of SNN = 130 GeV at the Relativistic Heavy Ion Collider using STAR. Balance functions for peripheral collisions have widths consistent with model predictions based on a superposition of nucleon-nucleon scattering. Widths in central collisions are smaller, consistent with trends predicted by models incorporating late hadronization.     

Joint statistics of the Lagrangian acceleration and velocity in fully developed turbulence

We report experimental results on the joint statistics of the Lagrangian acceleration and velocity in highly turbulent flows. The acceleration was measured up to a microscale Reynolds number R(lambda)=690 using high speed silicon strip detectors from high energy physics. The acceleration variance was observed to be strongly dependent on the velocity, following a Heisenberg-Yaglom-like u(9/2) increase. However, the shape of the probability density functions of the acceleration component conditioned on the same component of the velocity when normalized by the acceleration variance was observed to be independent of velocity and to coincide with the unconditional probability density function of the acceleration components. This observation imposes a strong mathematical constraint on the possible functional form of the acceleration probability distribution function.