Reduction of Escherichia coli O157:H7 in Biofilms Using Bacteriophage BPECO 19

Biofilm formation is a growing concern in the food industry. Escherichia coli O157:H7 is one of the most important foodborne pathogens that can persists in food and food‐related environments and subsequently produce biofilms. The efficacy of bacteriophage BPECO 19 was evaluated against three E. coli O157:H7 strains in biofilms. Biofilms of the three E. coli O157:H7 strains were grown on abiotic (stainless steel, rubber, and minimum biofilm eradication concentration [MBEC^TM] device) and biotic (lettuce) surfaces at different temperatures. The effectiveness of bacteriophage BPECO 19 in reducing preformed biofilms on these surfaces was further evaluated by treating the surfaces with a phage suspension (10⁸ PFU/mL) for 2 h. The results indicated that the phage treatment significantly reduced (P  < 0.05) the number of adhered cells in all the surfaces. Following phage treatment, the viability of adhered cells was reduced by ≥3 log CFU/cm², 2.4 log CFU/cm², and 3.1 log CFU/peg in biofilms grown on stainless steel, rubber, and the MBEC^TM device, respectively. Likewise, the phage treatment reduced cell viability by ≥2 log CFU/cm² in biofilms grown on lettuce. Overall, these results suggested that bacteriophages such as BPECO 19 could be effective in reducing the viability of biofilm‐adhered cells.     

Facile synthesis and electrochemical performance of ordered LiNi0.5Mn1.5O4 nanorods as a high power positive electrode for rechargeable Li-ion batteries

One-dimensional ordered LiNi_0.5Mn_1.5O₄ nanorods have been fabricated and investigated for use as a high power cathode in rechargeable Li-ion batteries. These highly crystalline nanorods, with an ordered spinel structure and diameters and lengths around 130 nm and 1.2 μm, respectively, were synthesized in two steps by using a hydrothermal reaction to produce β-MnO₂ nanorods followed by solid-state lithiation. Electrochemical analysis showed the superior performance of nanorods as a cathode in Li-ion half cells. The specific charge and discharge capacities were found to be 120 and 116 mAh g⁻¹ at a 0.5 C rate, and 114 and 111 mAh g⁻¹ at a 1 C rate between 3.5 and 5.0 V vs. Li⁺/Li. Moreover, the nanorods exhibit high power capability, maintaining capacities of 103 and 95 mAh g⁻¹ at specific currents of 732.5 and 1465 mA g⁻¹ (5 and 10 C rates), respectively.     

Surface passivation of crystalline silicon wafer via hydrogen plasma pre-treatment for solar cells

The carrier lifetime of crystalline silicon wafers that were passivated with hydrogenated silicon nitride (SiN_x:H) films using plasma enhanced chemical vapor deposition was investigated in order to study the effects of hydrogen plasma pre-treatment on passivation. The decrease in the native oxide, the dangling bonds and the contamination on the silicon wafer led to an increase in the minority carrier lifetime. The silicon wafer was treated using a wet process, and the SiN_x:H film was deposited on the back surface. Hydrogen plasma was applied to the front surface of the wafer, and the SiN_x:H film was deposited on the hydrogen plasma treated surface using an in-situ process. The SiN_x:H film deposition was carried out at a low temperature (<350 °C) in a direct plasma reactor operated at 13.6 MHz. The surface recombination velocity measurement after the hydrogen plasma pre-treatment and the comparison with the ammonia plasma pre-treatment were made using Fourier transform infrared spectroscopy and secondary ion mass spectrometry measurements. The passivation qualities were measured using quasi-steady-state photoconductance. The hydrogen atom concentration increased at the SiN_x:H/Si interface, and the minority carrier lifetime increased from 36.6 to 75.2 μs. The carbon concentration decreased at the SiN_x:H/Si interfacial region after the hydrogen plasma pre-treatment.     

Survey of undeclared soy allergen levels in the most frequently recalled food categories with or without precautionary labelling

A comprehensive study was designed to determine the frequency and levels of soy allergen in packaged bakery and snack food products. A representative sample of products with no soy allergen disclosed on the label was analysed using two widely used enzyme-linked immunosorbent assay (ELISA) methods. Samples were chosen that either had no soy identified on the product label or which had a soy precautionary statement. Among 558 bakery and snack products, soy protein was detected in 17% of the products using the Neogen (NE) kit and 11% of the products using the Elisa Systems (ES) kit. The disagreement rates between kits were 8.8% for bakery products and 3.3% for snack products. Overall soy protein was detected at higher frequency in bakery products than in snack foods. Among 284 bakery samples, soy protein was detected in 25% of the samples with no precautionary statement and 19% of the samples which had a precautionary statement. Among 274 snack samples, soy protein was detected in 11% of the samples with no precautionary statement and 9% of the samples which had a precautionary statement. The sample repeatability was at an acceptable level (< 9%) for each method and food commodity. The reproducibility between kits was 23% for bakery foods and 36% for snack foods. None of the bakery (21) and snack (6) products without precautionary labelling (measured level > 5 ppm) had a higher level of soy protein per serving compared with the eliciting dose₁₀ (ED₁₀) of 10.6 mg for soy allergic patients. But the level of soy protein per serving may be clinically relevant to a subpopulation of soy allergic patients if a more stringent eliciting dose is applied. These findings emphasise that suitable detection methodologies and references doses are crucial for labelling accuracy and the safety of soy allergic consumers.     

Patterning of pH sensitive fluorescent bipyridazine derivatives

A pH sensitive pipeprazine substituted bipyridazine fluorophore, DPP-BPDZ was explored as a pH sensor in solution and thin film state. Greenish highly fluorescent solution of the DPP-BPDZ with fluorescence quantum yield of 0.63 showed fluorescence decrease as the acetic acid concentration of the media was increased. The fluorescence quenching was correlated linearly with the content of acetic acid dose and attributed to the protonation at the terminal piperazine group. An acid sensitive film was fabricated using a transparent polymeric host (PMMA) and the DPP-BPDZ dye molecules as a guest. The resultant bright green fluorescent film (1.4 microm thick) showed exponential decrease of the fluorescence intensity as the pH of the dipping solution was decreased. In the range of pH below 4.5, the film sensitivity to pH was higher than the pH range over 4.5. A patternable film sensor was fabricated by introducing a photo acid generator (PAG) layer on the dye layer. Fluorescence patterns was formed on the film sensor through a photo-mask by relatively weak power of UV light (0.4 mW/cm2). Fluorescent line patterns having 10 microm line width were obtained with high fluorescence contrast between the patterns.     

Oxygen ion drifted bipolar resistive switching behaviors in TiO2-Al electrode interfaces

The rutile TiO₂ thin film involving two different top electrodes (Pt and Al) clearly shows the unipolar and bipolar resistive switching transitions which are dependent on the degree of redox properties at TiO₂ layer-electrode interfaces. Detailed current level analysis coupled with Auger electron spectroscopy measurements of the Pt/TiO₂/Pt and Al/TiO₂/Pt structures in the on/off switching states revealed the implication of oxygen ion migration induced chemical reaction at the Al-TiO₂ interfaces. Therefore, it is expected that the bipolar transition nature of resistive switching with an Al electrode is the resulting formation of a thin AlO_x layer due to redox reaction at Al-TiO₂ layer interfaces.     

Decoding, Performance Analysis, and Optimal Signal Designs for Coordinate Interleaved Orthogonal Designs

Space-time block codes (STBC) using coordinate interleaved orthogonal designs (CIOD) proposed recently by Khan and Rajan allow single-complex symbol decoding and offer higher data rates than orthogonal STBC. In this paper, we present the channel decoupling property of CIOD codes. A new general maximum likelihood method is derived, enabling the calculation of the symbol pair-wise error probability and union bound (UB) on symbol error rate (SER). Extensive simulation results show that the UB is within 0.1 dB from the simulated SER when SER < 10^-2. The UB thus can be used to accurately predict and optimize the performance of CIOD codes. Furthermore, a new signal design combining signal rotation and power allocation is presented for constellations with uneven powers of real and imaginary parts such as rectangular quadrature amplitude modulation.     

6.1 GHz 4.6 mW CMOS divide-by-55/56 prescaler

A divide-by-55/56 phase switching prescaler based on odd phase signals is proposed. The odd phase signals for phase switching are generated by a divide-by-7 injection-locked frequency divider. A simple topology with a high operating frequency and a low power consumption is obtained. Implemented with a standard 0.18 mm CMOS process, the prescaler is able to work from 3.2 to 6.1 GHz with a maximum measured power consumption of 4.6 mW from a 1.8 V supply voltage.