Interactive inhibition of meat spoilage and pathogenic bacteria by lysozyme,nisin and EDTA in the presence of nitrite and sodium chloride at 24 degrees C

To develop a nisin- and lysozyme-based antimicrobial treatment for use with processed ham and bologna, in vitro experiments were conducted to determine whether inhibition enhancing interactions occur between the antimicrobials lysozyme, chrisin (a commercial nisin preparation), EDTA, NaCl and NaNO₂. Inhibitory interactions were observed between a number of agents when used against specific pathogenic and spoilage bacteria. The observed interactions included lysozyme with EDTA (Enterococcus faecalis and Weissella viridescens), chrisin with EDTA (all Gram-positive organisms), EDTA with NaCl (Escherichia coli, Salmonella enterica serovar Typhimurium, Serratia grimesii), EDTA with nitrite (E. coli, Lactobacillus curvatus, Leuconostoc mesenteroides, Listeria monocytogenes, S. Typhimurium), chrisin with nitrite (Lc. mesenteroides, L. monocytogenes), and NaCl with nitrite (S. Typhimurium, Shewanella putrefaciens). Previous reports have described interactions between nisin with EDTA that resulted in enhanced antimicrobial effect against Gram-negative bacteria, or lysozyme with nisin against Gram-positive bacteria. These interactions were not observed in these experiments. We observed that unlike previous studies, these experiments were conducted on growing cells in nutrient broth, rather than under conditions of nutrient limitation. We propose that screening of antimicrobials for use in food systems in nutrient-deficient systems is inappropriate and that new protocols should be developed.     

Processes influencing rainfall deposition of mercury in Florida

The primary goal of the Florida Atmospheric Mercury Study (FAMS) was to quantify the atmospheric deposition of Hg throughout Florida. Monthly integrated precipitation and weekly integrated particulate samples were collected at 10 sites in Florida for periods ranging from 2 to 5 yr. The monthly rainfall across the state and the concentrations of Hg in wet-only and bulk deposition increased by a factor of 2-3 during the summertime "wet season" (May-October). These parallel increases in rainfall amount and Hg concentration resulted in 5-8-fold increases in rainfall Hg deposition during the wet season. The annual volume-weighted Hg concentrations ranged from 14 +/- 2 to 16 +/- 2 ng/L across southern Florida, and the annual rainfall Hg fluxes ranged from 20 +/- 3 to 23 +/- 3 micrograms m-2 yr-1. The weekly integrated particulate Hg concentrations in southern Florida were low (4.9-9.3 pg/m3) and did not exhibit strong seasonal variability. Considering the pronounced seasonal pattern in rainfall Hg deposition, the relatively uniform summertime rainfall Hg concentrations, and the low concentrations of particulate Hg, we conclude that processes other than particulate Hg transport and scavenging govern rainfall Hg deposition in southern Florida. We hypothesize that long-range transport of reactive gaseous Hg (RGM) species coupled with strong convective thunderstorm activity during the summertime represents > 50% of the Hg deposition in southern Florida. Model calculations indicate that local anthropogenic particulate Hg and RGM emissions account for 30-46% of the summertime rainfall Hg deposition across the southern Florida peninsula.     

The efficiency of gravity distribution devices for on-site wastewater treatment systems

A detailed analysis of different types of gravity distribution devices, designed to split on-site wastewater effluent equally between percolation trenches, has been carried out both in the laboratory and also in the field under realistic loading conditions. Five different types of distribution device have been compared: a V-notch distribution box, stilling chamber box, T-splitters with and without baffles and tipping bucket device. The trials carried out in the laboratory with clean water showed that flow distribution for all devices was sensitive to both the off-level installation angles and variable flow rates, with the most stable performance achieved using the T-splitters with baffles and tipping bucket devices. In parallel to this, the on-site flow regime experienced at two sites was continuously monitored using a tipping bucket and data-logger over eighteen month periods, finding that the most common flow rates at the distribution unit were in the range of 0.1-2.5 L/min. The on-site performance of these devices receiving both septic tank and secondary treated effluent showed that significant solid deposition and biofilm development had severely affected the equal distribution between the trenches, hence highlighting the need for regular maintenance to ensure efficient performance over time after installation.     

An Examination of the Relationship Between Transition State Geometry in Hydron Transfer Reactions and the Temperature Dependence of the Primary Kinetic Isotope Effect

Several recent papers by Kwart feature hydron transfer reactions in which the primary kinetic isotope effect is temperature independent over wide temperature ranges. It has been asserted (without theoretical justification) that this phenomenon is associated with transition state X….H….Y bond angles which are significantly less than 180°, whereas normal temperature dependence may be associated with transition states in which the angle is close to 180°. This work employs model calculations of isotope effects, principally for [1,5] H-shifts in 1,3-pentadiene, to examine Kwarts's hypothesis. No model tested yielded a temperature-independent isotope effect of substantial magnitude. The transition state (angle = 133°) was located on the MNDO potential energy surface and the isotope effect, calculated by a new and fast computational procedure, was again temperature dependent. Model calculations of secondary hydrogen isotope effects were carried out. When bending motions of the non-reacting hydrogens were coupled to C….H stretching modes in the force constant matrix, it was found that kH/kD was greater than the equilibrium secondary isotope effect, k_H/K_D, and that k_H/k_D for hydrogen transfer exceeded k_H/k_D for deuteron transfer when simple tunnel corrections were incorporated. A novel interpretation to account for the observation of some temperature-independent isotope effects is advanced.     

Aylesford新闻纸厂生产综述

Ａｙｌｅｓｆｏｒｄ新闻纸有限公司于 １９９３年由 ＳＣＡ森林产品和 Ｍｏｎｄｉ Ｅｕｒｏｐｅ建立的。随后，２．５亿英镑（合３．７５亿美元）的投资项目以新闻纸机（～＃１４机）和脱墨车间，还有１个完全自动化包装线和仓库、２个联合热电厂以及１个水和污水处理工厂的投产而宣告完成。 这一最新的发展只是Ａｙｌｅｓｆｏｒｄ众多造纸历史事件之一，早在１９２１年Ａｙｌｅｓｆｏｒｄ就已经开始制造新闻纸。在～＃１４机之前已有的新闻纸机（～＃１３机）已经运行了将近４０年，并于１９８２年成为英国第一台利用１００％脱墨纤维制造…