The effect of salt and fibre direction on water dynamics,distribution and mobility in pork muscle: A low field NMR study

The effect of salt concentration and fibre orientation on water within the meat matrix was investigated by low-field nuclear magnetic resonance (LF-NMR), water-binding capacity (WBC), diffusion studies and histological analysis. Pork M. longissimus thoracis et lumborum samples were cured with 5.7, 15.3 or 26.3% w/w NaCl at a parallel or perpendicular fibre direction. NMR transverse (T₂) relaxation identified three water components (T_2b, T₂₁ and T₂₂) which all exhibited characteristics correlated to WBC. Results indicated that T_2b increases with increasing NaCl concentration. Increasing intra-myofibrillar water and decreasing extra-myofibrillar water resulted in the highest WBC. Water diffused more quickly into the extra-myofibrillar space in samples cured at a parallel fibre direction. This water remained loosely bound in samples cured with the saturated solution (26.3% w/w NaCl) leading to decreased WBC. This study provides further information on water binding within the meat matrix by applying the results of LF-NMR to traditional water-binding theories.     

Fate of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella on fresh-cut celery

Illnesses from Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella have been associated with the consumption of numerous produce items. Little is known about the effect of consumer handling practices on the fate of these pathogens on celery. The objective of this study was to determine pathogen behavior at different temperatures under different storage conditions. Commercial fresh-cut celery was inoculated at ca. 3 log CFU/g onto either freshly cut or outer uncut surfaces and stored in either sealed polyethylene bags or closed containers. Samples were enumerated following storage for 0, 1, 3, 5, and 7 days when held at 4 °C or 12 °C, and after 0, 8, and 17 h, and 1, and 2 days when held at 22 °C. At 4 °C, all populations declined by 0.5–1.0 log CFU/g over 7 days. At 12 °C, E. coli O157:H7 and Salmonella populations did not change, while L. monocytogenes populations increased by ca. 0.5 log CFU/g over 7 days. At 22 °C, E. coli O157:H7, Salmonella, and L. monocytogenes populations increased by ca. 1, 2, or 0.3 log CFU/g, respectively, with the majority of growth occurring during the first 17 h. On occasion, populations on cut surfaces were significantly higher than those on uncut surfaces. Results indicate that populations are reduced under refrigeration, but survive and may grow at elevated temperatures.     

Fuels for urban transit buses: a cost-effectiveness analysis

Public transit agencies have begun to adopt alternative propulsion technologies to reduce urban transit bus emissions associated with conventional diesel (CD) engines. Among the most popular alternatives are emission controlled diesel buses (ECD), defined here to be buses with continuously regenerating diesel particle filters burning low-sulfur diesel fuel, and buses burning compressed natural gas (CNG). This study uses a series of simplifying assumptions to arrive at first-order estimates for the incremental cost-effectiveness (CE) of ECD and CNG relative to CD. The CE ratio numerator reflects acquisition and operating costs. The denominator reflects health losses (mortality and morbidity) due to primary particulate matter (PM), secondary PM, and ozone exposure, measured as quality adjusted life years (QALYs). We find that CNG provides larger health benefits than does ECD (nine vs six QALYs annually per 1000 buses) but that ECD is more cost-effective than CNG (dollar 270 000 per QALY for ECD vs dollar 1.7 million to dollar 2.4 million for CNG). These estimates are subject to much uncertainty. We identify assumptions that contribute most to this uncertainty and propose potential research directions to refine our estimates.     

Indication of geographic variaritions of organochlorine concentrations in the blubber of Antarctic Weddell seals (Leptonychotes weddelli)

A sample cleanup procedure using microwave-assisted extraction (MAE) with focus open vessel (FOV-MAE) technique was validated for the determination of organohalogen compounds in the blubber of a Weddell seal (Leptonychotes Weddelli) from the Antarctic (King George Island, 62 degrees 14' S, 58 degrees 40' W). Good reproducibility in replicate analysis of samples confirms the suitability of the method for samples with very low persistent organic pollutant (POP) concentrations. The method was used to analyze three additional blubber samples of Weddell seals from King George Island. This community of Weddell seals showed the lowest DDT (11-19 microg/kg) and PCB (1-2.5 microg/kg) concentrations so far detected in comparable marine mammals from all over the world. The concentrations determined in the four Weddell seals were also typical for the population at King George Island. However, the DDT and PCB concentrations on King George Island were one order of magnitude lower than in samples of the same species from other sites in the Antarctic (located between 69 degrees S and 78 degrees S). This suggests a wide variability of organohalogen levels in the Antarctic, depending on the geographic site. King George Island (62 degrees S) is found at the outskirts of the Antarctic Peninsula, i.e., the region with the mildest climate in the Antarctic. Low organohalogen levels at this site were attributed to a lower degree of condensation in comparison with locations further south. Most of the reference samples were taken in the Weddell and Ross Seas, i.e., from coastlines as close as possible to the pole. Consequently, other sites on the same latitude as the Weddell and Ross Seas are found on the Antarctic continent This raises the question whether high proportions of organohalogens are being deposited on the Antarctic continent where they are not available to marine organisms. Although this hypothesis has to be proven in follow-up studies, our study clearly demonstrates that it is complicated, if not impossible, to derive time trends in concentrations of POPs in biota from different reference sites in the Antarctic.     

Adsorption of natural organic matter onto carbonaceous surfaces: atomic force microscopy study

The microscopic structure of carbonaceous surfaces exposed to natural organic matter (NOM) under aqueous conditions has been explored using atomic force microscopy (AFM). Dismal Swamp Water was used as the NOM source, while highly ordered pyrolytic graphite (HOPG) served as a surrogate for the graphene sheets that characterize the surface of many carbonaceous materials in aquatic environments. Under acidic conditions, the HOPG surface was covered with a densely packed monolayer of NOM molecules. In some cases, aggregates of well-defined, individual NOM molecules were observed that exhibited a degree of registry with respect to the HOPG substrate. This suggests that adsorbate-substrate interactions play a role in moderating the structure of the adsorbate layer. As the pH increased, the concentration of adsorbed NOM decreased systematically because of increasingly repulsive interactions between adsorbates. Increasing the ionic strength produced a modest increase in the concentration of adsorbed NOM. Ca2+ ions exerted a more pronounced influence on both the surface coverage of adsorbed NOM molecules and the size of individual adsorbates because of the effects of intermolecular complexation. In contrast to the spherical structures observed by AFM under aqueous conditions, adsorbed NOM formed a mixture of "ringlike" assemblies and larger aggregates upon drying.     

A chemometric approach to detection and characterization of multiple protein conformers in solution using electrospray ionization mass spectrometry

Protein ion charge state distributions in electrospray ionization mass spectra have a potential to provide a wealth of information on protein dynamics, because they contain contributions from all protein conformers present in solution. Such ionic contributions often overlap, limiting the amount of useful information that can be extracted from the spectra. This difficulty is overcome in the present work by using a chemometric approach, which allows spectral deconvolution to be carried out and information on individual protein conformers to be extracted. Experiments are carried out by acquiring a series of spectra over a range of near-native and denaturing conditions to ensure significant changes in the conformers' populations. A total number of protein conformers sampled in the course of the experiments is determined by subjecting the set of collected spectra to singular value decomposition. Ionic contributions of each conformer to the total signal are then determined using a supervised optimization routine. Validation of the method has been carried out by monitoring acid- and alcohol-induced equilibrium states of well-characterized model proteins, chymotrypsin inhibitor 2 (two states), ubiquitin (three states) and apo-myoglobin (four states). For each of the model proteins, a new chemometric procedure yielded a picture of protein dynamics that was in excellent agreement with their documented behavior (as studied with other biophysical tools). The new method appears to be well-suited for monitoring protein dynamics in highly heterogeneous systems consisting of multiple proteins sampling a range of conformational states.     

LOW-TEMPERATURE AUTOFRETTAGE: AN IMPROVED TECHNIQUE TO ENHANCE THE FATIGUE RESISTANCE OF THICK-WALLED TUBES AGAINST PULSATING INTERNAL PRESSURE

Abstract— It is shown that autofrettage at low temperatures is superior to autofrettage at room temperature in enhancing the fatigue resistance of thick-walled tubes against pulsating internal pressure. The physical reason is based on the well-known temperature dependence of the mechanical behaviour of metals and alloys which generally exhibit an enhancement of both the yield stress and strain hardening behaviour at lower temperatures. As a consequence, significantly larger compressive residual hoop stresses can be introduced during pressurization at low temperatures than at room temperature. Experimental data obtained on thick-walled tubes of the metastable austenitic stainless steel AISI 304 L which were subjected to pulsating internal pressure at room temperature after autofrettage at temperatures between-110°C and room temperature are presented. These data demonstrate convincingly the advantages offered by low-temperature autofrettage in enhancing both the fatigue life in the finite-life region and the fatigue endurance limit in comparison with autofrettage at room temperature. In conclusion, some specific materials requirements for optimum low-temperature autofrettage performance are discussed.     

Acoustic radiation force enhances targeted delivery of ultrasound contrast microbubbles: in vitro verification

Recent research has shown that targeted ultrasound contrast microbubbles achieve specific adhesion to regions of intravascular pathology, but not in areas of high flow. It has been suggested that acoustic radiation can be used to force free-stream microbubbles toward the target, but this has not been verified for actual targeted contrast agents. We present evidence that acoustic radiation indeed increases the specific targeted accumulation of microbubbles. Lipid microbubbles bearing an antibody as a targeting ligand were infused through a microcapillary flow chamber coated with P-selectin as the target protein. A 2.0 MHz ultrasonic pulse was applied perpendicular to the flow direction. Microbubble accumulation was observed on the flow chamber surface opposite the transducer. An acoustic pressure of 122 kPa enhanced microbubble adhesion up to 60-fold in a microbubble concentration range of 0.25 x 10(6) to 75 x 106) ml(-1). Acoustic pressure mediated the greatest adhesion enhancement at concentrations within the clinical dosing range. Acoustic pressure enhanced targeting nearly 80-fold at a wall shear rate of 1244 s(-1), suggesting that this mechanism is appropriate for achieving targeted microbubble delivery in high-flow vessels. Microbubble adhesion increased with the square of acoustic pressure between 25 and 122 kPa, and decreased substantially at higher pressures.     

Preparation,stabilite et etude cristallographique preliminaire du compose Bi2Sn2O7

Our crystallochemistry investigation of the Bi₂O₃ - SnO₂ binary in the range of compositions between 60 and 75 SnO₂ moles percent, brings new evidence of the compound Bi₂Sn₂O₇. It has a tetragonal structure ($\text{a}\text{= 21.31}\text{A}\text{?}$, $\text{c}\text{= 21.53}\text{A}\text{?}$), related to the pyrochlore structure.From this study arises a new problem about the influence of Bi3+ ion on the doubling of the crystalline parameters.