Efficacy of low concentration neutralised electrolysed water and ultrasound combination for inactivating Escherichia coli ATCC 25922, Pichia pastoris GS115 and Aureobasidium pullulans 2012 on stainless steel coupons

The sanitising effect of low concentration neutralised electrolysed water (LCNEW, pH: 7.0, free available chlorine (FAC): 4 mg/L) combined with ultrasound (37 kHz, 80 W) on food contact surface was evaluated. Stainless steel coupon was chosen as attachment surface for Escherichia coli ATCC 25922, Pichia pastoris GS115 and Aureobasidium pullulans 2012, representing bacteria, yeast and mold, respectively. The results showed that although LCNEW itself could effectively reduce survival population of E. coli ATCC 25922, P. pastoris GS115 and low concentration A. pullulans 2012 in planktonic status, LCNEW combined with ultrasound showed more sanitising efficacy for air-dried cells on coupons, with swift drops: 2.2 and 3.1 log CFU/coupon reductions within 0.2 min for E. coli ATCC 25922 and P. pastoris GS115, respectively and 1.0 log CFU/coupon reductions within 0.1 min for A. pullulans 2012. Air-dried cells after treatment were studied by atomic force microscopy (AFM)/optical microscopy (OM) and protein leakage analyses further. All three strains showed visible cell damage after LCNEW and LCNEW combined with ultrasound treatment and 1.41 and 1.73 μg/mL of protein leakage were observed for E. coli ATCC 25922 and P. pastoris GS115, respectively after 3 min combination treatment, while 6.22 μg/mL of protein leakage for A. pullulans 2012 after 2 min combination treatment. For biofilms, LCNEW combined with ultrasound also significantly reduced the survival cells both on coupons and in suspension for all three strains. The results suggest that LCNEW combined with ultrasound is a promising approach to sanitise food equipment.     

SiO2胶体探针的制备及其在表面力测定中的应用

采用一种新方法——双向三维移动平台法制备胶体探针，该方法使用两个三雏移动平台，同时将CCD与长工作距离显微镜集成，组成视频监视系统来监控探针的整个制备过程，方便了操作。利用此自组装装置制备的二氧化硅胶体探针在原子力显微镜上进行力曲线测量，将分析数据与Ducker的经典论文进行对照，得到较为理想的结果。     

Wavelength dependent laser-induced etching of Cr-O doped GaAs: Morphology studies by SEM and AFM

The laser induced etching of semi-insulating GaAs 〈100〉 is carried out to create porous structure under super- and sub-bandgap photon illumination (h v). The etching mechanism is different for these separate illuminations where defect states play the key role in making distinction between these two processes. Separate models are proposed for both the cases to explain the etching efficiency. It is observed that under sub-bandgap photon illumination the etching process starts vigorously through the mediation of intermediate defect states. The defect states initiate the pits formation and subsequently pore propagation occurs due to asymmetric electric field in the pore. Formation of GaAs nanostructures is observed using scanning electron (SEM) and atomic force microscopy (AFM).     

Structural entropy in detecting background patterns of AFM images

Structural entropy was developed for detecting the type of localization in charge distributions on a finite grid, especially in mesoscopic electronic systems. However, it is possible to detect and analyze superstructures, i.e., topologies consisting of more structures with different types of localization properties. In the definition of the structural entropy, the von Neumann entropy of the system is divided into two parts: first, the extension entropy, which is simply the logarithm of the occupation number; the second part is the structural entropy. On a structural entropy versus logarithm of the spatial filling factor map, the different types of localizations follow different, well-characterized curves. Spatial filling factor measures the percentage of the “filled” (i.e., high intensity) pixels of the image.An atomic force microscopy (AFM) image can be interpreted as some kind of charge distribution on a grid: after normalization, the darkness (or lightness) of the pixels fulfills all the necessary conditions. AFM image artifacts can be detected by plotting the structural entropy versus the logarithm of the spatial filling factor maps of the images. Not only the type of an added large-scale Gaussian, parabolic, exponential, or other function can be identified, but also by careful study of the curves belonging to the structures, the parameters can be detected, too.     

AFM Scratching for Adhesion Studies of Thin Polymer Coatings on Steel

Abstract

Atomic force miscroscopy (AFM) scratching at constant applied forces was used to quantify the adhesion of polymer coatings to cold rolled steel (CRS) and to study the effectiveness of a pretreatment for improving the adhesion. The pretreatment was a phosphate-free zirconia-based coating. Thin layers of commercially available epoxy, acrylic and polyester-based polymer coatings, were applied to polished or pretreated cold rolled steel substrates and the surface was scratched at the edge of the polymer coatings with the AFM tip at increasing values of normal loads until the coating was removed. Adhesion strengths were determined from the minimum tip-sample interaction force and number of cycles (scans) at a particular applied force. The pretreatment significantly improved adhesion of the epoxy and acrylic-based coatings on CRS. Adhesion of the acrylic-based coating was found to be better than the epoxy coatings on the bare as well as pretreated steel. Adhesive strength of the polyester-based coating was inconclusive because it was very easily removed on application of small forces using the AFM tip. The AFM scratching technique was found to provide a quick, easy and effective way to make quantifiable comparisons in relative adhesive strengths of polymer coatings and the effect of pretreatments.     

Mapping micromechanical properties of soft polymer contact lenses

We present comparative micromechanical characterization of several commercial soft silicone hydrogel contact lenses, which allows for the examination of spatial distribution of different regions with local mechanical properties within the lens under practical wet conditions. We employ elastic contact mechanic model and corresponding analysis of force–distance curves collected with high-resolution atomic force microscopy measurements performed within elastic deformation limits. The measurements were performed on the lens cross section to map the micromechanical properties distribution within the sub-surface regions and bulk material of the different lens. In addition, we have studied topography and mechanical properties of the lens surfaces, which come into direct contact with the surface of the eye and eyelid. AFM images show high contrast distribution maps for the adhesive and mechanical properties of the different microstructured regions such as pores, lamellae and different material inclusions within the lenses. Additional indentation experiments allow for collection of quantitative data for micromechanical properties from different regions within the lens structure and correlate these data with lens-averaged macroscopic measurements available in the literature.     

Novel process for isolating fibrils from cellulose fibers by high‐intensity ultrasonication. II. Fibril characterization

High‐intensity ultrasonication with a batch process was used to isolate fibrils from several cellulose sources, and a mixture of microscale and nanoscale fibrils was obtained. The geometrical characteristics of the fibrils were investigated with polarized light microscopy, scanning electron microscopy, and atomic force microscopy. The results show that small fibrils with diameters ranging from about 30 nm to several micrometers were peeled from the fibers. Some fibrils were isolated from the fibers, whereas some were still on the fiber surfaces. The lengths of untreated and treated cellulose fibers were investigated by a fiber size analyzer. The crystallinities of some cellulose fibers were evaluated by wide‐angle X‐ray diffraction and Fourier transform infrared spectroscopy. The high‐intensity ultrasonication technique is an environmentally benign method and a simplified process that conducts fiber isolation and chemical modification simultaneously and helps significantly reduce the production cost of cellulose nanofibers and their composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A universal fluid cell for the imaging of biological specimens in the atomic force microscope

Recently, atomic force microscope (AFM) manufacturers have begun producing instruments specifically designed to image biological specimens. In most instances, they are integrated with an inverted optical microscope, which permits concurrent optical and AFM imaging. An important component of the set‐up is the imaging chamber, whose design determines the nature of the experiments that can be conducted. Many different imaging chamber designs are available, usually designed to optimize a single parameter, such as the dimensions of the substrate or the volume of fluid that can be used throughout the experiment. In this report, we present a universal fluid cell, which simultaneously optimizes all of the parameters that are important for the imaging of biological specimens in the AFM. This novel imaging chamber has been successfully tested using mammalian, plant, and microbial cells. Microsc. Res. Tech. 76:357–363, 2013. © 2013 Wiley Periodicals, Inc.     

Influence of N ion implantation on the corrosion and nano-structure of Ti samples

Nitrogen ions of 30 keV with different fluxes ranging from 5 × 10¹⁶ to 8 × 10¹⁷ ions/cm² were implanted in Ti foil of 1.8 mm thickness. X-ray diffraction (XRD) was used to obtain the structural characteristics, while atomic force microscope (AFM) was employed to obtain the surface morphology of the samples. The potentiodynamic method was employed to obtain corrosion resistance of the samples in NaCl (3.5%) solution. Titanium nitride formation was enhanced with increasing the nitrogen ion flux, while grain size and surface roughness of the samples were also increased. Optimum corrosion resistance was obtained for 5 × 10¹⁶ (N⁺ ions/cm²).     

Plasma modification of polylactic acid in a medium pressure DBD

In this paper, a dielectric barrier discharge (DBD) operating in different atmospheres (air, nitrogen, helium and argon) and at medium pressure is employed to modify the surface properties of polylactic acid (PLA). Chemical and physical changes on the plasma-treated surfaces are examined using contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. Results show that the discharge gas can have a significant influence on the chemical composition of the PLA surfaces: air and argon plasmas introduce oxygen-containing groups, while nitrogen discharges add nitrogen groups to the PLA surface. Quite surprisingly, also helium plasmas incorporate a small amount of nitrogen-containing functionalities: this observation can however be explained by the fact that the helium discharge operates in the glow mode. In the near future, it will be examined whether the performed plasma treatments can enhance PLA cell attachment and proliferation, which might open the door to many interesting biomedical applications.