Autonomic Recovery of Fiber/Matrix Interfacial Bond Strength in a Model Composite

Autonomic self‐healing of interfacial damage in a model single‐fiber composite is achieved through sequestration of ca. 1.5 μm diameter dicyclopentadiene (DCPD) healing‐agent‐filled capsules and recrystallized Grubbs’ catalyst to the fiber/matrix interface. When damage initiates at the fiber/matrix interface, the capsules on the fiber surface rupture, and healing agent is released into the crack plane where it contacts the catalyst, initiating polymerization. A protocol for characterizing the efficiency of interfacial healing for the single‐fiber system is established. Interfacial shear strength (IFSS), a measure of the bond strength between the fiber and matrix, is evaluated for microbond specimens consisting of a single self‐healing functionalized fiber embedded in a microdroplet of epoxy. The initial (virgin) IFSS is equivalent or enhanced by the addition of capsules and catalyst to the interface and up to 44% average recovery of IFSS is achieved in self‐healing samples after full interfacial debonding. Examination of the fracture interfaces by scanning electron microscopy reveals further evidence of a polyDCPD film in self‐healing samples. Recovery of IFSS is dictated by the bond strength of polyDCPD to the surrounding epoxy matrix.     

Cell Surface Engineering with Edible Protein Nanoshells

Natural protein (silk fibroin) nanoshells are assembled on the surface of Saccharomyces cerevisiae yeast cells without compromising their viability. The nanoshells facilitate initial protection of the cells and allow them to function in encapsulated state for some time period, afterwards being completely biodegraded and consumed by the cells. In contrast to a traditional methanol treatment, the gentle ionic treatment suggested here stabilizes the shell silk fibroin structure but does not compromise the viability of the cells, as indicated by the fast response of the encapsulated cells, with an immediate activation by the inducer molecules. Extremely high viability rates (up to 97%) and preserved activity of encapsulated cells are facilitated by cytocompatibility of the natural proteins and the formation of highly porous shells in contrast to traditional polyelectrolyte‐based materials. Moreover, in a high contrast to traditional synthetic shells, the silk proteins are biodegradable and can be consumed by cells at a later stage of growth, thus releasing the cells from their temporary protective capsules. These on‐demand encapsulated cells can be considered a valuable platform for biocompatible and biodegradable cell encapsulation, controlled cell protection in a synthetic environment, transfer to a device environment, and cell implantation followed by biodegradation and consumption of protective protein shells.     

Point and Interval Estimation Procedures for the Two-Parameter Weibull and Extreme-Value Distributions

Point estimators of parameters of the first asymptotic distribution of smallest (extreme) values, or, the extreme-value distribution, are surveyed and compared. Those investigated are maximum-likelihood and moment estimators, inefficient estimators based on only a few ordered observations, and various linear estimation methods. A combination of Monte Carlo approximations and exact small-sample and asymptotic results has been used to compare the expected loss (with loss equal to squared error) of these various point estimators. Since the logarithms of variates having the two-parameter Weibull distribution are variates from the extreme-value distribution, the investigation is applicable to the estimation of Weibull parameters. Interval estimation procedures are also discussed.     

Characterisation of malolactic conversion by Oenococcus oeni to reduce the acidity of apple juice

The high concentration of malic acid is responsible for the acidity and sourness in apple juice. Bio‐conversion of malic acid to lactic acid through malolactic conversion (MC) in apple juice using Oenococcus oeni was investigated. When apple juice was inoculated with O. oeni (1 × 10⁶ CFU mL^?1), over 90% of malic acid was converted into lactic acid within 96 h at room temperature. When pH of apple juice was adjusted to 4.1 prior to inoculation, MC was completed within 60 h. MC was enhanced at a higher temperature (30°C) when compared with room temperature. The rate of MC was directly proportional to the number of bacteria added and MC was completed within 24 h at 1 × 10⁹ CFU mL^?1 initial cell density. MC occurred equally under aerobic and anaerobic conditions. The sensory analysis of partial MC‐applied juice when compared against control revealed potential for use of MC for manufacture of low‐acid apple juice.     

Associations among nocturnal sleep,daytime intradialytic sleep,and mortality risk in patients on daytime conventional hemodialysis: US Renal Data System special study data

Fragmented nocturnal sleep is commonly reported by patients undergoing daytime conventional hemodialysis (CHD) and may be associated with higher mortality risk. Subjective sleepiness during CHD is also frequently observed. We examined the association of reported sleep fragmentation and nocturnal and daytime (intradialytic) sleep durations with survival in a national cohort of 1440 CHD patients who were interviewed in 2005–2007 in a phone survey conducted by the US Renal Data System. Patient survival was followed through September 30, 2010 in the US Renal Data System. A total of 76% of patients reported that they typically dozed off or slept during their treatment, and intradialytic dozing was especially common among patients whose treatment shift started before 1000 hours. There was a trend for patients who reported dozing during CHD to report nocturnal sleep fragmentation (60.4% vs. 55.1%; P = 0.07). With adjustment for intradialytic sleep and other covariates, nocturnal sleep fragmentation was not associated with survival. Mortality risk was higher for patients who reported sleeping 9 or more hours/night compared with the referent category of nocturnal sleep equal to 6–7 hours (hazard ratio: 1.50 [95% confidence interval: 1.04–2.17]; P = 0.03). Continued investigation of the association of timing and duration of sleep with hemodialysis patient outcomes is warranted.     

Physical activity and self‐reported symptoms of insomnia,restless legs syndrome,and depression: The comprehensive dialysis study

Symptoms of sleep and mood disturbances are common among patients on dialysis and are associated with significant decrements in survival and health‐related quality of life. We used data from the Comprehensive Dialysis Study (CDS) to examine the association of self‐reported physical activity with self‐reported symptoms of insomnia, restless legs syndrome (RLS), and depression in patients new to dialysis. The CDS collected data on physical activity, functional status, and health‐related quality of life from 1678 patients on either peritoneal (n = 169) or hemodialysis (n = 1509). The Human Activity Profile was used to measure self‐reported physical activity. Symptoms were elicited in the following manner: insomnia using three questions designed to capture difficulty in initiating or maintaining sleep, RLS using three questions based on the National Institutes of Health workshop, and depression using the two‐item Patient Health Questionnaire. We obtained data on symptoms of insomnia and depression for 1636, and on symptoms of RLS for 1622 (>98%) patients. Of these, 863 (53%) reported one of three insomnia symptoms as occurring at a persistent frequency. Symptoms of RLS and depression occurred in 477 (29%) and 451 (28%) of patients, respectively. The Adjusted Activity Score of the Human Activity Profile was inversely correlated with all three conditions in models adjusting for demographics, comorbid conditions, and laboratory variables. Sleep and mood disturbances were commonly reported in our large, diverse cohort of patients new to dialysis. Patients who reported lower levels of physical activity were more likely to report symptoms of insomnia, RLS, and depression.     

Design of Over-Stress Life-Test Experiments When Failure Times Have the Two-Parameter Weibull Distribution

This paper deals with estimation of reliability parameters when life testing is conducted at stress levels above that which would normally be applied in standard usage. A range of stress for testing is prescribed, and a two-parameter Weibull model for failure times is assumed. The logarithm of the Weibull scale parameter is assumed to be a polynomial function of known degree k of the reciprocal of stress level. The Weibull shape parameter is assumed to be independent of stress level.

The problem considered is that of determining the design for obtaining the least-squares-curve intercept with minimum variance at the nominal testing level. The design obtained specifies the number and location of stress levels in the prescribed range at which the life tests will be conducted and proportion of the total sample of specified size to be randomly allocated to each testing level.     

Biocompatibility analysis of an electrically-activated silver-based antibacterial surface system for medical device applications

The costs associated with the treatment of medical device and surgical site infections are a major cause of concern in the global healthcare system. To prevent transmission of such infections, a prophylactic surface system that provides protracted release of antibacterial silver ions using low intensity direct electric current (LIDC; 28 μA system current at 6 V) activation has been recently developed. To ensure the safety for future in vivo studies and potential clinical applications, this study assessed the biocompatibility of the LIDC-activated interdigitated silver electrodes-based surface system; in vitro toxicity to human epidermal keratinocytes, human dermal fibroblasts, and normal human osteoblasts, and antibacterial efficacy against Staphylococcus aureus and Escherichia coli was evaluated. The study concluded that the technological applications of the surface system for medical devices and surgical tools, which contact human tissues for less than 1.5 h, are expected to be self-sterilizing without causing toxicity in vivo.     

A two and half-year-performance evaluation of a field test on treatment of source zone tetrachloroethene and its chlorinated daughter products using emulsified zero valent iron nanoparticles

A field test of emulsified zero valent iron (EZVI) nanoparticles was conducted at Parris Island, SC, USA and was monitored for two and half years to assess the treatment of subsurface-source zone chlorinated volatile organic compounds (CVOCs) dominated by tetrachloroethene (PCE) and its chlorinated daughter products. Two EZVI delivery methods were used: pneumatic injection and direct injection. In the pneumatic injection plot, 2180 L of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of CVOCs. In the direct injection plot, 572 L of EZVI were injected to treat an estimated 0.155 kg of CVOCs. After injection of the EZVI, significant reductions in PCE and trichloroethene (TCE) concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for PCE (>85%) and TCE (>85%) and a significant increase in the mass flux of ethene. There were significant reductions in total CVOC mass (86%); an estimated reduction of 63% in the sorbed and dissolved phases and 93% reduction in the PCE DNAPL mass. There are uncertainties in these estimates because DNAPL may have been mobilized during and after injection. Following injection, significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed. In contrast, dissolved sulfate and pH decreased in many wells. The apparent effective remediation seems to have been accomplished by direct abiotic dechlorination by nanoiron followed by biological reductive dechlorination stimulated by the corn oil in the emulsion.