Assurance of energy efficiency and data security for ECG transmission in BASNs

With the technological advancement in body area sensor networks (BASNs), low cost high quality electrocardiographic (ECG) diagnosis systems have become important equipment for healthcare service providers. However, energy consumption and data security with ECG systems in BASNs are still two major challenges to tackle. In this study, we investigate the properties of compressed ECG data for energy saving as an effort to devise a selective encryption mechanism and a two-rate unequal error protection (UEP) scheme. The proposed selective encryption mechanism provides a simple and yet effective security solution for an ECG sensor-based communication platform, where only one percent of data is encrypted without compromising ECG data security. This part of the encrypted data is essential to ECG data quality due to its unequally important contribution to distortion reduction. The two-rate UEP scheme achieves a significant additional energy saving due to its unequal investment of communication energy to the outcomes of the selective encryption, and thus, it maintains a high ECG data transmission quality. Our results show the improvements in communication energy saving of about 40%, and demonstrate a higher transmission quality and security measured in terms of wavelet-based weighted percent root-mean-squared difference.     

Photovoltaics literature survey (no. 92)

In order to help keep readers up‐to‐date in the field each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, including IEEE Transactions on Electron Devices, Journal of Applied Physics, Applied Physics Letters, Progress in Photovoltaics and Solar Energy Materials and Solar Cells. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions please email Santosh Shrestha at s.shrestha@unsw.edu.au.     

Photovoltaics literature survey (No. 107)

In order to help keep readers up to date in the field, each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, including IEEE Transactions on Electron Devices, Journal of Applied Physics, Applied Physics Letters, Progress in Photovoltaics and Solar Energy Materials and Solar Cells. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions, please email Santosh Shrestha at s.shrestha@unsw.edu.au.     

Encapsulation of Photosensitizers and Upconversion Nanocrystals in Lipid Micelles for Photodynamic Therapy

Photodynamic therapy (PDT) is a promising method for cancer therapy. However, it is constrained by limited penetration depth of visible light, hydrophobicity of photosensitizers, and lack of tumor targeting. In this work, the photosensitizer zinc phthalocyanine (ZnPc) and upconversion nanocrystals (UCNs) are encapsulated into OQPGA‐PEG/RGD/TAT lipid micelles. The UCNs acting as a nanotransducer convert deep‐penetrating near‐infrared (NIR) light to visible light for activating the photosensitizer. OQPGA‐PEG/RGD/TAT lipid micelles are used as a carrier for the photosensitizer, with improved biocompatibility and cancer‐targeting ability. The results show that the photosensitizer ZnPc‐ and UCNs‐loaded OQPGA‐PEG/RGD/TAT lipid micelles are nanoparticles with an average size of 25 nm. The lipid micelle nanoparticles are stable in water with low leakage of photosensitizer. The absorption peak of the photosensitizer overlaps with the emission peak of UCNs, so the visible fluorescence emitted from the UCNs upon excitation by the NIR laser at 980 nm can activate the photosensitizer to produce singlet oxygen for PDT. The targeting RGD peptide and cell‐penetrating TAT peptide on the surface help the nanoparticles getting into cancer cells. The OQPGA‐PEG/RGD/TAT lipid micelles encapsulated with both the photosensitizer ZnPc and UCNs could be used for targeted PDT by using deep‐penetrating NIR light as the light source.     

Photovoltaics literature survey (No. 103)

In order to help keep readers up‐to‐date in the field, each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, incl uding IEEE Transactions on Electron Devices, Journal of Applied Physics, Applied Physics Letters, Progress in Photovoltaics, and Solar Energy Materials and Solar Cells. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also, note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions, please email Santosh Shrestha at s.shrestha@unsw.edu.au.     

A low-power biologically-inspired chaotic oscillator with process and temperature tolerance

This paper presents a low-power, biologically-inspired silicon neuron based implementation of a chaotic oscillator circuit. The silicon neuron structure is based on Hodgkin–Huxley neuron model. Subthreshold MOSFET and current reuse techniques have been utilized to achieve a low-power consumption of 180.30 nW for the room temperature (27 °C) and typical process corner. The chaotic behavior of the circuit is confirmed by calculating the largest Lyapunov exponent. A sensitivity analysis of the proposed chaotic oscillator shows that the circuit maintains the chaotic behavior for five different process corners within the temperature range of 0–60 °C.     

Effect of heat and time-period on the growth of ZnO nanorods by sol–gel technique

Sol–gel routes to metal oxide nanoparticles in organic solvents under exclusion of water have become a versatile alternative to aqueous methods. We focus on the preparation of well-aligned ZnO nanorod arrays using non-aqueous sol–gel synthesis route, where ZnO nanorods arrays have been grown on glass substrates. This work provides a systematic study of controlled morphology and crystallinity of ZnO nanorod arrays. The investigation demonstrates that the synthesis process conditions of ZnO thin film have strong influences on the morphology and crystallinity of the ZnO nanorod arrays grown thereon, where non-aqueous process offers the possibility of better understanding and controlling the reaction pathways on the molecular level, enabling the synthesis of nanomaterials with high crystallinity and well-defined, uniform particle morphologies. Here the annealing temperature plays an important role on the growth of nanostructures of the ZnO grains and nanorod arrays. The scanning electron microscopy (SEM) image shows that the growth of ZnO nanorod arrays are high-quality single crystals growing along the c-axis perpendicular to the substrates. A detailed analysis of the growth characteristics of ZnO nanostructures as functions of growth time is also reported.     

Polycationic chitosan-conjugated photosensitizer for antibacterial photodynamic therapy

The complex nature of bacterial cell membrane and structure of biofilm has challenged the efficacy of antimicrobial photodynamic therapy. This study was aimed to synthesize a polycationic chitosan-conjugated rose bengal (CSRB) photosensitizer and test its antibiofilm efficacy on Enterococcus faecalis (gram positive) and Pseudomonas aeruginosa (gram negative) using photodynamic therapy. During experiments, CSRB was tested along with an anionic photosensitizer rose bengal (RB) and a cationic photosensitizer methylene blue (MB) for uptake and killing efficacy on 7-day-old E. faecalis and P. aeruginosa biofilms. Microbiological culture based analysis was used to analyze the cell viability, while laser scanning confocal microscopy (LSCM) was used to examine the structure of biofilm. The synthesized CSRB showed absorbance spectrum similar to the RB. The concentration of CSRB uptaken by both the bacterial biofilms was significantly higher than that of RB and MB (P < 0.05). Photoactivation resulted in significantly higher elimination of both bacterial biofilms sensitized with CSRB than RB and MB. The structure of biofilm under LSCM was found to be disrupted following CSRB treatment. The present study highlighted the importance of inherent cell membrane permeabilizing effect of chitosan and increased cell/biofilm uptake of conjugated photosensitizer to produce significant antibiofilm efficacy during photodynamic therapy.