LO phonon–plasmon coupled modes and carrier mobilities in heavily Se-doped Ga(As, N) thin films

We use Raman scattering to study the LO–plasmon coupled modes (LOPCMs) of n-type GaAs_1−x N _x epilayers grown by molecular beam epitaxy (0.1% ≤ x ≤ 0.36%). We find that the LOPCMs are heavily damped in n-GaAs_1−x N _x even for x as low as 0.1%. From a lineshape analysis based on the hydrodynamical model, we evaluate the lifetime of the LOPCMs in our samples. We compare the values thus obtained with the corresponding Hall mobilities. We find that both quantities decrease strongly with increasing x, which can be attributed to N-related alloy scattering of conduction band electrons in the GaAs_1−x N _x alloy.     

上海地区中青年女性文胸号型选择情况调查与分析

通过对444名长期居住（15年以上）在上海地区、学历在高中以上且年龄为25～45岁的女性胸部细部尺寸的测量,按照国际标准文胸号型尺寸计算出该444名女性理论应选择的文胸号型（Theoretical Choice）;并通过问卷调查的方式,获得了该444名女性实际生活中依靠主观感觉所选择的文胸号型（ActualChoice...     

Evaluation of current operating standards for chlorine dioxide in disinfection of dump tank and flume for fresh tomatoes

Standard postharvest unit operations that rely on copious water contact, such as fruit unloading and washing, approach the criteria for a true critical control point in fresh tomato production. Performance data for approved sanitizers that reflect commercial systems are needed to set standards for audit compliance. This study was conducted to evaluate the efficacy of chlorine dioxide (ClO(2)) for water disinfection as an objective assessment of recent industry-adopted standards for dump tank and flume management in fresh tomato packing operations. On-site assessments were conducted during eight temporally distinct shifts in two Florida packinghouses and one California packinghouse. Microbiological analyses of incoming and washed fruit and dump and flume system water were evaluated. Water temperature, pH, turbidity, conductivity, and oxidation-reduction potential (ORP) were monitored. Reduction in populations of mesophilic and coliform bacteria on fruit was not significant, and populations were significantly higher (P < 0.05) after washing. Escherichia coli was near the limit of detection in dump tanks but consistently below the detection limit in flumes. Turbidity and conductivity increased with loads of incoming tomatoes. Water temperature varied during daily operations, but pH and ORP mostly remained constant. The industry standard positive temperature differential of 5.5°C between water and fruit pulp was not maintained in tanks during the full daily operation. ORP values were significantly higher in the flume than in the dump tank. A positive correlation was found between ORP and temperature, and negative correlations were found between ORP and turbidity, total mesophilic bacteria, and coliforms. This study provides in-plant data indicating that ClO(2) can be an effective sanitizer in flume and spray-wash systems, but current operational limitations restrict its performance in dump tanks. Under current conditions, ClO(2) alone is unlikely to allow the fresh tomato industry to meet its microbiological quality goals under typical commercial conditions.     

Improving the keeping quality of pomegranate fruit by intermittent warming

 Mollar pomegranates (Punica granatum, Punicaceae) were stored at 0  °C or 5  °C and 95% relative humidity (RH) for 80 days. Intermittent warming (IW) cycles of 1 day at 20  °C every 6 days, during which time the fruit had been stored at 0  °C or 5  °C, followed by a shelf-life period of 7 days at 15  °C and 70% RH were applied. IW during storage at 0  °C was the best treatment for maintaining the red skin colour as at harvest. However the red colour of the arils (hue angle) was kept better under warming at 5  °C. Although significant changes in the individual anthocyanins were observed in all treatments, particularly after the shelf-life period, the total anthocyanin content of the juice at harvest was maintained. While storage at 0  °C avoided decay although increased the risk of chilling injuries such us pitting and husk scald, 5  °C-storage reduced these injuries but fungal attacks were not inhibited. After the shelf-life period, IW alleviated chilling injuries without any incidence of decay. Warming treatments gave very good results with respect to storage and the keeping quality of pomegranates, particularly when applied during storage at 0  °C. Received: 10 February 1998 / Revised version: 24 April 1998     

Quality Changes and Shelf-Life Prediction of a Fresh Fruit and Vegetable Purple Smoothie

The sensory, microbial, and bioactive quality changes of untreated (CTRL) and mild heat-treated (HT; 90 °C/45 s) smoothies were studied and modelled throughout storage (5, 15 and 25 °C). The overall acceptability was better preserved in HT samples being highly correlated (hierarchical clustering) with the flavour. The sensory quality data estimated smoothie shelf-life (CTRL/HT) of 18/55 (at 5 °C), 4.5/12 (at 15 °C) and 2.4/5.8 (at 25 °C) days. The yeast and mould growth rate was lower in HT compared to CTRL while a lag phase for mesophiles/psychrophiles was observed in HT-5/15 °C. HT and 5 °C storage stabilised the phenolic content. Ferric reducing antioxidant power reported the best correlation (R ² = 0.94) with the studied bioactive compounds, followed by ABTS (R ² = 0.81) while DPPH was the total antioxidant capacity method with the lowest adjustment (R ² = 0.49). Conclusively, modelling was used to estimate the shelf-life of a smoothie based on quality retention after a short-time, high-temperature heat treatment that better preserved microbial and nutritional quality during storage.     

Keeping quality and safety of minimally fresh processed melon

Fresh-cut Amarillo melon was stored under passive modified atmosphere packaging (MAP) for 14 days at 5 °C. Three commercial films were tested: microperforated polypropylene (MPP), bioriented PP (BPP), and oriented PP (OPP). As a control, a macroperforated PP film was used. The effect of a citric acid dip treatment (0.52 mM) on the quality of the melon pieces packaged in OPP film was also evaluated. A similar final gas composition (4 kPa O2 plus 12–13 kPa CO2) within packages was achieved by using the three tested films. This atmosphere was effective for maintaining sensorial quality and microbial safety and for avoiding weight loss and translucency. When citric acid dip was applied, a reduction of microbial counts, a low discoloration, an increase of lightness, and a general improvement of visual appearance were found. However, after 14 days of storage, neither MAP treatments nor citric acid dip were enough to avoid softening of at least 23%, although the highest value (32%) was found in control pieces. Taking into account safety, quality attributes and consumer acceptance, shelf life of fresh processed melon stored under the studied MAP conditions could be stabilised for 10 days.     

Quality of broccoli as influenced by film wrapping during shipment

'Shogun' broccoli florets were film-wrapped and stored for 7 days at 1 °C to simulate a maximum period of commercial shipment. After cold storage, florets were kept for 2.5 days at 20 °C to simulate a retail sale period. For wrapping, polyvinyl chloride (PVC) 9 µm thickness and low-density polyethylene (LDPE) 11, 15, and 20 µm thickness were used. Soluble solids content, pH, titratable acidity, weight loss, physiological disorders, visual quality, and gas composition within packages were monitored. Gas composition (about 18% O₂ and 1% CO₂ during cold storage and about 16% O₂ and 2-3% CO₂ during shelf life), overall quality, and yellowing and browning of the florets were at similar levels among the films studied. However, weight loss was about sixty times lower for all LDPE films than for PVC film. After shelf life the best results were obtained by using 15 µm LDPE. This polymeric film could be a good alternative to PVC for wrapping broccoli for commercial shipment purposes, particularly to those countries where use of PVC has been forbidden.     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.     

Increasing the oxidative stability of poly(dicyclopentadiene) aerogels by hydrogenation

Ring opening metathesis polymerization (ROMP) of cycloolefins is a promising new route for the preparation of polymeric aerogels. The resulting unsaturation in the polymer backbone, however, makes these particular systems susceptible to oxidative degradation under ambient conditions. One method to increase the oxidative stability of these aerogels is to hydrogenate the material. In the present study, hydrogenation of poly(dicyclopentadiene) gels was achieved through thermolysis of para-toluenesulfonyl hydrazide in the presence of tripropylamine followed by solvent exchange and supercritical drying to form the hydrogenated aerogel (H-pDCPD). Aerogels were prepared with varying densities and were characterized by FTIR-ATR, elemental analysis, BET, SEM, XPS, DSC and TGA. The oxidative stability of H-pDCPD aerogels over pDCPD was investigated through thermolysis in the presence of atmospheric oxygen. We report herein the synthesis and characterization of this new material.