Effect of multiblock copolymers in polymer blends

The use of multiblock copolymers for the compatibilization of immiscible polymer blends is controversially discussed in the literature. Investigations have been carried out to estimate the effect of multiblock copolymers containing segments of a liquid crystalline polyester (LCP) and polysulfone (PSU) segments in blends of the based homopolymers. One goal was to determine whether multiblock copolymers provide an opportunity for compatibilizing PSU/LCP blends. By using PSU/LCP multiblock copolymers with different molecular weights of the blocks in the appropriate binary, solution-casted blends, it was shown that the interpenetration of the polysulfone phase of the block copolymer and the PSU matrix leads to an improved miscibility of the blend. This effect is retained in ternary blends of PSU, LCP, and the multiblock copolymer, assuming a certain critical molecular weight of the multiblock copolymer segments. In addition, some mechanical characteristics of PSU/LCP melt blends such as the E-modulus and fracture strength are improved by adding long-segmented multiblock copolymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2293–2309, 1997     

Major bridge development in Hong Kong,China—past,present and future

The first “modern” type of vehicular bridge was built in Hong Kong China in the 1920s. The need for an efficient transportation system to cope with population growth and enable economic development has demanded the construction of more and more bridges since the middle of the 20th century. By 2007, Hong Kong had a total of about 1300 vehicular bridges. Four of these bridges, including the Tsing Ma Bridge, Kap Shui Mun Bridge, Ting Kau Bridge, and the cable-stayed bridge on the Hong Kong- Shenzhen Western Corridor, are considered to be major bridges supported by cables. Currently, the Stonecutters Bridge on Route No. 8 is under construction and is expected to be completed in late 2009. At the same time, the Hong Kong-Zhuhai-Macao Bridge will be in its detailed design stage soon. While efforts have been made by bridge builders to construct these giant structures, the upkeeping of these valuable assets at a high standard and ensuring their continuous functioning and performance during their intended lifespans will be another important task for bridge engineers. Wind and structural health monitoring system (WASHMS) will play a key role in this respect.     

High Intensity Ultrasound for Salmonella Enteritidis Inactivation in Culture and Liquid Whole Eggs

High intensity ultrasound (HIU) continues to be researched as a nonthermal inactivation technology of appeal to food manufacturers. The advantages of HIU include maintenance of product quality, freshness, product homogenization, along with simultaneous inactivation of pathogens. Besides, it is simple, relatively inexpensive, and easily adaptable to most processing environments. This study investigated the effect of HIU for Salmonella Enteritidis inactivation in culture and liquid whole eggs (LWEs) to decrease egg‐associated outbreaks. Overnight S. Enteritidis cultures and spiked LWE (both at 8 log CFU/mL) were treated with 20‐kHz HIU for 0, 1, 5, 10, and 30 min (n = 6) in a temperature‐controlled system, not to exceed 20 °C, and replicated thrice. At each time point, samples were enumerated on XLT4 agar and morphologically analyzed using scanning electron microscopy, with measurements of color and rheological properties. Our results revealed significant reduction of healthy S. Enteritidis cells up to 3.6 log CFU/mL and 2.3 log CFU/25 mL after HIU treatment of merely 10 min of overnight culture and 30 min in LWE, respectively (P < 0.05). After 5 and 10‐min HIU treatment, significant reduction of 1.4‐log CFU/25 mL healthy S. Enteritidis in LWE was obtained (P < 0.05). Even at 1‐min exposure time, HIU showed significant 1.9 log CFU/mL reduction of cultures (P < 0.05); however, no log‐reduction was observed in LWE after 1 min. Scanning electron micrographs showed increased cell structural damage using longer HIU exposure. For product color changes, lower redness and yellowness of LWE were observed visually and instrumentally after 5‐min HIU treatment (P < 0.05). The rheological properties of LWE measured at 0 to 200 s^?1 shear rate, showed that shear stress of HIU‐treated LWEs decreased after 5‐min HIU exposure, but increased after 30‐min treatment. This study demonstrated that HIU shows promise for rapid Salmonella control in LWE and other liquid foods, as an alternative inactivation method for use in hurdle approaches.     

Antimicrobial Effects of Quillaja saponaria Extract Against Escherichia coli O157:H7 and the Emerging Non‐O157 Shiga Toxin‐Producing E. coli

Natural alternate methods to control the spread of Shiga toxin‐producing Escherichia coli (STEC) are important to prevent foodborne outbreaks. Quillaja saponaria aqueous bark extracts (QE), cleared by the U.S. Food and Drug Administration as a natural flavorant, contain bioactive polyphenols, tannins, and tri‐terpenoid saponins with anti‐inflammatory and antimicrobial activity. The objective of this study was to determine the effects of commercial QE against E. coli O157:H7 and non‐O157 strains over 16 h at 37 °C and RT. Overnight cultures of 4 E. coli O157:H7 strains and 6 non‐O157 STECs in Tryptic Soy Broth (TSB) were washed and resuspended in phosphate‐buffered saline (PBS, pH 7.2), and treated with QE and controls including citric acid (pH 3.75), sodium benzoate (0.1% w/w), acidified sodium benzoate (pH 3.75) or PBS for 6 h or 16 h. Recovered bacteria were enumerated after plating on Tryptic Soy Agar, from duplicate treatments, replicated thrice and the data were statistically analyzed. The 4 QE‐treated E. coli O157:H7 strains from initial ～7.5 log CFU had remaining counts between 6.79 and 3.5 log CFU after 16 h at RT. QE‐treated non‐O157 STECs showed lower reductions with remaining counts ranging from 6.81 to 4.55 log CFU after 16 h at RT.  Incubation at 37 °C caused reduction to nondetectable levels within 1 h, without any significant reduction in controls. Scanning electron microscopy studies revealed damaged cell membranes of treated bacteria after 1 h at 37 °C. QE shows potential to control the spread of STECs, and further research in model food systems is needed.     

Compensation of Pinhole Defects in Food Packages by Application of Iron‐based Oxygen Scavenging Multilayer Films

To protect sensitive food products from oxidative deterioration, multilayer barrier film systems and also modified atmosphere packaging are widely applied. However, the preservation of food quality in such packaging systems may be compromised by the presence of defects in the sealing layer of the films, especially when these are below a critical size, typically the detection limit of standard leak testers of 10 µm. The addition of an oxygen scavenger (OS) layer in barrier film structures could therefore provide extended protection against O₂ penetration through such defects. In this study, O₂ absorption of different multilayer film structures including an iron‐based OS were investigated under defined gas atmospheres. Measurement cells were thereby covered with plastic films of defined O₂ permeability to simulate conditions in a food package during storage with pinhole defect sizes of 10 and 17 µm. The results indicated that the OS film structures applied could only compensate for a defect size of 10 µm in the sealing layer. Analysis of the O₂ absorption of different multilayer film structures at 85% and 100% relative humidity showed that higher humidity accelerates the activation of the scavenger. After full activation, the scavenger kinetics are the same for 85% and 100% relative humidity. Long‐term storage experiments using the most effective film structure from the preliminary experiments were carried out to compare O₂ absorption of a snack food product in packages with and without an OS. The analyzed linear gradient of the reaction of the OS film and food product, respectively, indicated first‐order reaction kinetics with corresponding reaction constants calculated to be K (food product) 0.021 mg (O₂) mbar (O₂)^?1 day^?1 and K (OS film) 0.066 mg (O₂) mbar (O₂)^?1 day^?1. The reaction velocity of the OS was thus three times faster than that of the food. The applicability of OS multilayer film systems to compensate a critical pinhole defect size of 10 µm for sensitive food products could therefore be confirmed. The measurement of quality parameters for the status of lipid oxidation processes would help to verify this result. Copyright © 2012 John Wiley & Sons, Ltd.     

A Bayes Sampling Allocation Scheme for Stratified Finite Populations With Hyperbinomial Prior Distributions

When sampling is carried out independently for the K strata of a finite stratified dichotomous population (defectives vs. standard items), and the number Z_i of defectives per stratum sample is observed, the corresponding probability function for X = (X_i , …, x_K ) is the product of hypergeometric functions which depend on the sample sizes n_i , the stratum sizes N_i , and the number of defectives M_i in the stratum (i = 1, …, K). It is assumed that prior information is available about the M_i 's which can be expressed, by suitable choice of the parameters a_i and b_i , as the product of independent hyperbinomial functions.

In each stratum the cost per observation is a known constant. Using squared error loss function, the prior Bayes risk is found for the linear function of interest,

and the optimum allocation of sample sizes is found, the one for which the prior Bayes risk is minimum when the total sampling budget is fixed.     

Chemistry, biology, and QSAR studies of substituted biaryl hydroxamates and mercaptoacetamides as HDAC inhibitors-nanomolar-potency inhibitors of pancreatic cancer cell growth

The histone deacetylases (HDACs) are able to regulate gene expression, and inhibitors of the HDACs (HDACIs) hold promise in the treatment of cancer as well as a variety of neurodegenerative diseases. To investigate the potential for isoform selectivity in the inhibition of HDACs, we prepared a small series of 2,4'-diaminobiphenyl ligands functionalized at the para-amino group with an appendage containing either a hydroxamate or a mercaptoacetamide group and coupled to an amino acid residue at the ortho-amino group. A smaller series of substituted phenylthiazoles was also explored. Some of these newly synthesized ligands show low-nanomolar potency in HDAC inhibition assays and display micromolar to low-nanomolar IC(50) values in tests against five pancreatic cancer cell lines. The isoform selectivity of these ligands for class I HDACs (HDAC1-3 and 8) and class IIb HDACs (HDAC6 and 10) together with QSAR studies of their correlation with lipophilicity are presented. Of particular interest is the selectivity of the mercaptoacetamides for HDAC6.