Clostridium tertium bacteremia: 2 cases and review

Clostridium tertium bacteremia is unusual, seen most often with gastrointestinal disease and/or neutropenia. Two cases are described. The first was a 19-yr-old female with acute leukemia, who developed gastrointestinal symptoms and C. tertium bacteremia while neutropenic. The second was a 57-yr-old female with quiescent ulcerative colitis, who presented with fever, rigors and epigastric pain. Four organisms including C. tertium were isolated from blood cultures. This patient responded to broad spectrum antimicrobial therapy, whereas the first patient required the addition of specific agents to recover. C. tertium is aerotolerant and thus can be misidentified as a Bacillus or Corynebacterium spp. Our isolates had a distinctive Gram stain morphology, were catalase negative and failed to sporulate aerobically--this aided in the recognition of this significant Gram-positive bacillus.     

The glass transition temperature of partially cured polymers as a non-equilibrium parameter and its effect on observed dynamic mechanical behavior

Observations of time dependent behaviors of polymeric systems are often made with the assumption that the glass transition temperature will remain constant during the course of the experiment. This assumption may not be valid for partially cured thermosetting system, where additional cure can increase the glass transition temperature. The observed behavior can be expressed as a time derivative function of two independent variables, the experimental temperature and the state of the system. With proper assumptions, these two variables can be reduced to a single parameter (T ? T_g), whose time derivative will give terms representing the temperature and curing effect separately. Dynamic mechanical measurements have been made on partially cured systems, and the effects of the additional cure on the observed properties are observed. The seemingly complex experimental observations can be qualitatively interpreted with the change of the parameter (T ? T_g).     

Fracture toughness (KQ) testing with a mini-compact tension (CT) specimen

A testing method using the Rheometrics Mechanical Spectrometer as the loading instrument to measure the fracture toughness K_Q, which is related to a specific sample geometry and dimensions (half-inch compact tension) is reported. The small sample size requirement makes it attractive to do fracture toughness testing on newly synthesized material for preliminary material study and comparison purposes. Commercially available epoxy resins were used to check the procedure at different temperatures (?150° to 250°C). An empirical crack length averaging method was used that appears to give constant K_Q values independent of the a/W ratio values. The fracture surfaces were studied using scanning electron microscopy.     

Spectral resolution in conjunction with polar plots improves the accuracy and reliability of FLIM measurements and estimates of FRET efficiency

A spectrograph with continuous wavelength resolution has been integrated into a frequency‐domain fluorescence lifetime‐resolved imaging microscope (FLIM). The spectral information assists in the separation of multiple lifetime components, and helps resolve signal cross‐talking that can interfere with an accurate analysis of multiple lifetime processes. This extends the number of different dyes that can be measured simultaneously in a FLIM measurement. Spectrally resolved FLIM (spectral‐FLIM) also provides a means to measure more accurately the lifetime of a dim fluorescence component (as low as 2% of the total intensity) in the presence of another fluorescence component with a much higher intensity. A more reliable separation of the donor and acceptor fluorescence signals are possible for Förster resonance energy transfer (FRET) measurements; this allows more accurate determinations of both donor and acceptor lifetimes. By combining the polar plot analysis with spectral‐FLIM data, the spectral dispersion of the acceptor signal can be used to derive the donor lifetime – and thereby the FRET efficiency – without iterative fitting. The lifetime relation between the donor and acceptor, in conjunction with spectral dispersion, is also used to separate the FRET pair signals from the donor alone signal. This method can be applied further to quantify the signals from separate FRET pairs, and provide information on the dynamics of the FRET pair between different states.     

Study on lycopene and antioxidant contents variations in tomatoes under air-drying process

ABSTRACT:  Effects of factors such as tomato cultivars, drying temperatures (40, 80, and 120 °C), and drying time (0 to 240 min) on tomato lycopene and the major antioxidant contents (MACs, herein as the sum of total phenolics and total flavonoids) during an air-drying process were investigated. The results showed that lycopene contents increased under all the drying temperatures during the first 60 min. However, the red tomato cultivars, that is, HR, SN, and TTL, exhibited a significant decrease in lycopene contents under 120 °C after drying for 75 min. According to the experimental data, an MAC threshold value of 500 mg/100 g dry matter of tomato is proposed. When the MAC is lower than this value during air-drying, lycopene contents in all tomato cultivars would drop rapidly. In addition, the tomatoes in yellow color group, containing more MACs initially and retaining more MACs under air-drying at 40 to 80 °C, are proposed to be the proper tomato cultivars for thermal processing.     

Amino acid, fatty acid, and mineral profiles of materials recovered from rainbow trout (Oncorhynchus mykiss) processing by-products using isoelectric solubilization/precipitation

ABSTRACT:  Protein, lipid, and insolubles (bones, skin, scales, fins, insoluble protein, and more) were recovered from rainbow trout processing by-products by means of isoelectric solubilization/precipitation at basic pH and acidic pH. Isoelectric solubilization/precipitation of the trout processing by-products resulted in the recovery of protein that was higher ( P < 0.05) in essential amino acids (EAAs), non-EAAs, and total EAA/total AA ratio when compared to the processing by-products. Basic pH treatments yielded a higher ( P < 0.05) content of EAAs than the acidic pH treatments. Nutritional quality of the recovered protein was high based on EAAs meeting the FAO/WHO/UNU recommendations for adults. The presence of omega-3 and omega-6 fatty acids (ω-3, ω-6 FAs) and the ω-3/ω-6 ratio in the recovered lipids were similar to the trout processing by-products, indicating that the pH treatments had no effect on these FAs. Ca and P contents of the processing by-products exceeded the recommended dietary allowances (RDA), but Fe and Mg did not. Basic pH treatments yielded protein with the lowest ( P < 0.05) amount of minerals and the highest ( P < 0.05) amount of Ca, P, and Mg in the insolubles when compared to acidic pH. The isoelectric solubilization/precipitation of the processing by-products effectively removed minerals from the recovered protein without removal of the bones, skin, scales, fins, and so on, prior to processing. The results indicated that isoelectric solubilization/precipitation, particularly at basic pH, permitted recovery of high-quality protein and lipids from fish processing by-products for human food uses; also, the recovered insolubles may be used in animal feeds as a source of minerals.     

Ceramic fibres from polymer precursor containing Si-O-Ti bonds

By the reaction between organosilicon compounds and titanium alkoxides, polymers (atom ratio Ti/Si = 0.045 to 0.12) as the precursors for ceramic fibre were synthesized. Titanium in the precursors was bonded to organosilicon compounds in the Si-O-Ti bond. The synthesis process of the fibre is melt-spinning of the precursor, curing of the precursor fibre, and its heat-treatment. Curing was achieved by cross-linking of the polymer by the oxidation of Si-H bonds or hydrolysis of Ti-OR bonds in the precursor. The formation mechanism of the precursors and their pyrolysis process were examined in an inert gas atmosphere and in a vacuum. It was shown that the Si-O-Ti bond in the precursors is cleaved by pyrolysis of the Ti-O bond, so that TiC is formed. The tensile strength of the ceramic fibre obtained, is relatively high even by the heat-treatment at temperatures higher than 1200° C. Further, the Young's modulus is little changed.     

A nonoxidative sensor based on a self-doped polyaniline/carbon nanotube composite for sensitive and selective detection of the neurotransmitter dopamine

Most of the current techniques for detection of dopamine exploit its ease of oxidation. However, the oxidative approaches suffer from a common problem. The products of dopamine oxidation can react with ascorbic acid present in samples and regenerate dopamine again, which severely limits the accuracy of detection. In this paper, we report a nonoxidative approach to electrochemically detect dopamine with high sensitivity and selectivity. This approach takes advantage of the high performance of our newly developed poly(anilineboronic acid)/carbon nanotube composite and the excellent permselectivity of the ion-exchange polymer Nafion. The binding of dopamine to the boronic acid groups of the polymer with large affinity affects the electrochemical properties of the polyaniline backbone, which act as the transduction mechanism of this nonoxidative dopamine sensor. The unique reduction capability and high conductivity of single-stranded DNA functionalized, single-walled carbon nanotubes greatly improved the electrochemical activity of the polymer in physiological buffer, and the large surface area of the carbon nanotubes largely increased the density of the boronic acid receptors. The high sensitivity along with the improved selectivity of this sensing approach is a significant step forward toward molecular diagnosis of Parkinson's disease.