Grafting of bovine serum albumin proteins on plasma-modified polymers for potential application in tissue engineering

In this work, an influence of bovine serum albumin proteins grafting on the surface properties of plasma-treated polyethylene and poly-l-lactic acid was studied. The interaction of the vascular smooth muscle cells with the modified polymer surface was determined. The surface properties were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, nano-LC-ESI-Q-TOF mass spectrometry, electrokinetic analysis, and goniometry. One of the motivations for this work is the idea that by the interaction of the cell with substrate surface, the proteins will form an interlayer between the cell and the substrate. It was proven that when interacting with the plasma-treated high-density polyethylene and poly-l-lactic acid, the bovine serum albumin protein is grafted on the polymer surface. Since the proteins are bonded to the substrate surface, they can stimulate cell adhesion and proliferation.     

Experimental validation of a simple approximation to determine the linewidth of a laser from its frequency noise spectrum

Laser frequency fluctuations can be characterized either comprehensively by the frequency noise spectrum or in a simple but incomplete manner by the laser linewidth. A formal relation exists to calculate the linewidth from the frequency noise spectrum, but it is laborious to apply in practice. We recently proposed a much simpler geometrical approximation applicable to any arbitrary frequency noise spectrum. Here we present an experimental validation of this approximation using laser sources of different spectral characteristics. For each of them, we measured both the frequency noise spectrum to calculate the approximate linewidth and the actual linewidth directly. We observe a very good agreement between the approximate and directly measured linewidths over a broad range of values (from kilohertz to megahertz) and for significantly different laser line shapes.     

Contrast enhancement of medical images using fuzzy set theory and nonsubsampled shearlet transform

Noises and artifacts are introduced in medical images during the process of imaging and transmission, resulting in reduced definition and lack of detail. Therefore, a contrast enhancement method, based on fuzzy set theory and nonsubsampled shearlet transform (NSST), is proposed. First, the original image is decomposed into several high-frequency components and a low-frequency component by NSST. Then, the threshold method is used to remove noises in the high-frequency components. In addition, a linear stretch is used to improve the overall contrast in the low-frequency component. Then, the reconstruct image is reconstructed by applying the inverse NSST to the processed high-frequency and low-frequency components. Finally, the fuzzy contrast is used to improve the detail information and global contrast in the reconstruct image. Experimental results indicate that, relative to contrast algorithms, the peak signal-to-noise ratio of the proposed method is improved by approximately 18%, and the root mean square error (RMSE) is optimized to approximately 48%. The proposed method also improves the image definition and texture information. Moreover, when compared with the Improved Fuzzy Contrast Combined Adaptive Threshold in NSCT for Medical Image Enhancement, the processing time (time) of this proposed method optimizes about 86%, which can obviously improve the computational efficiency of this method.     

Piezotronic Tuning of Potential Barriers in ZnO Bicrystals

Coupling of magnetic, ferroelectric, or piezoelectric properties with charge transport at oxide interfaces provides the option to revolutionize classical electronics. Here, the modulation of electrostatic potential barriers at tailored ZnO bicrystal interfaces by stress‐induced piezoelectric polarization is reported. Specimen design by epitaxial solid‐state transformation allows for both optimal polarization vector alignment and tailoring of defect states at a semiconductor–semiconductor interface. Both quantities are probed by transmission electron microscopy. Consequently, uniaxial compressive stress affords a complete reduction of the potential barrier height at interfaces with head‐to‐head orientation of the piezoelectric polarization vectors and an increase in potential barrier height at interfaces with tail‐to‐tail orientation. The magnitude of this coupling between mechanical input and electrical transport opens pathways to the design of multifunctional electronic devices like strain triggered transistors, diodes, and stress sensors with feasible applications for human–computer interfacing.     

Incremental learning of chunk data for online pattern classification systems

This paper presents a pattern classification system in which feature extraction and classifier learning are simultaneously carried out not only online but also in one pass where training samples are presented only once. For this purpose, we have extended incremental principal component analysis (IPCA) and some classifier models were effectively combined with it. However, there was a drawback in this approach that training samples must be learned one by one due to the limitation of IPCA. To overcome this problem, we propose another extension of IPCA called chunk IPCA in which a chunk of training samples is processed at a time. In the experiments, we evaluate the classification performance for several large-scale data sets to discuss the scalability of chunk IPCA under one-pass incremental learning environments. The experimental results suggest that chunk IPCA can reduce the training time effectively as compared with IPCA unless the number of input attributes is too large. We study the influence of the size of initial training data and the size of given chunk data on classification accuracy and learning time. We also show that chunk IPCA can obtain major eigenvectors with fairly good approximation.     

Numerical simulation of combined screw compressor–expander machines for use in high pressure refrigeration systems

Recent interest in natural refrigerants has created a new impetus for studies of CO₂ as a working fluid in vapour compression systems for refrigeration and air conditioning. Two major drawbacks to its use are the very high pressure differences required across the compressor and the large efficiency losses associated with the throttling process in the refrigeration cycle. It is shown how these disadvantages can be minimised by the use of a screw machine both to compress the gas and use the expansion process to recover power. Both these functions can be performed simultaneously, using only one pair of rotors, in a configuration that partially balances out the forces induced by the pressure difference and hence, reduces the bearing loads to an acceptable level. A further feature is the use of rotors, which seal on both contacting surfaces so that the same profile may be used for the expander and the compressor sections. This enables the rotors performing both these functions to be machined or ground in the same cutting operation and then separated by machining a parting slot in them. Computational Continuum Mechanics comprising both, fluid flow and structural analysis is used in this paper for the investigation of fluid-solid interaction in such machines.     

Solution properties of poly(fluorostyrene-co-chlorostyrene) copolymers. I. Light scattering,differential refractometry and viscometry

The weight-average molecular weights (M?_w) of nominally random, unfractionated copolymers of ortho- and para-fluorostyrene and ortho- and para-chlorostyrene were determined by light scattering measurements in tetrahydro-furan, toluene, carbon tetrachloride and chloroform. It was shown that there is no significant variation in measured M?_w in the various solvents, a finding indicating that the copolymers are not compositionally heterogeneous. Intrinsic viscosity measurements in the same solvents established a consistent relationship between [n] and M?_w despite the differences in copolymer compositions. It was not possible to establish a similar relationship between the second virial coefficient A₂ and M?_w. It was concluded that measurements of the specific refractive index increment could be used for determining copolymer composition if the measurements were performed in thermodynamically poorer solvents. The results established for the Mark-Houwink constant α, intrinsic viscosity, and A₂ values indicated that these solvated copolymer molecules are in a less expanded conformation than are polystyrene molecules of similar molecular weights in a given solvent.