Reversible and irreversible low-pressure membrane foulants in drinking water treatment: Identification by principal component analysis of fluorescence EEM and mitigation by biofiltration pretreatment

With the increased use of membranes in drinking water treatment, fouling - particularly the hydraulically irreversible type - remains the main operating issue that hinders performance and increases operational costs. The main challenge in assessing fouling potential of feed water is to accurately detect and quantify feed water constituents responsible for membrane fouling. Utilizing fluorescence excitation-emission matrices (EEM), protein-like substances, humic and fulvic acids, and particulate/colloidal matter can be detected with high sensitivity in surface waters. The application of principal component analysis to fluorescence EEMs allowed estimation of the impact of surface water constituents on reversible and irreversible membrane fouling. This technique was applied to experimental data from a two year bench-scale study that included thirteen experiments investigating the fouling potential of Grand River water (Ontario, Canada) and the effect of biofiltration pre-treatment on the level of foulants during ultrafiltration (UF). Results showed that, although the content of protein-like substances in this membrane feed water (= biofiltered natural water) was much lower than commonly found in wastewater applications, the content of protein-like substances was still highly correlated with irreversible fouling of the UF membrane. In addition, there is evidence that protein-like substances and particulate/colloidal matter formed a combined fouling layer, which contributed to both reversible and irreversible fouling. It is suggested that fouling transitions from a reversible to an irreversible regime depending on feed composition and operating time. Direct biofiltration without prior coagulant addition reduced the protein-like content of the membrane feed water which in turn reduced the irreversible fouling potential for UF membranes. Biofilters also decreased reversible fouling, and for both types of fouling higher biofilter contact times were beneficial.     

In situ Raman spectroscopy to monitor the hydrolysis of acetal in microreactors

In order to obtain a better understanding of the physical and chemical processes within micromixers or microreactors and to optimize these devices it is necessary to monitor the concentrations within the microchannels. To get chemical information, laser Raman spectroscopy can be used. This method is very selective for individual chemical compounds, allows a spatial resolution of 10 μm within fluids and a quantitative analysis. We examined the hydrolysis of the acetal 2,2-dimethoxypropane to acetone and methanol in the presence of hydrogen ions as catalyst. This reaction can be used to characterize micromixers. The aim of this work is the in situ monitoring of concentrations of acetal and its products, acetone and methanol, during the hydrolysis of acetal within a T-shaped micromixer with a channel width of 0.4 mm and a channel depth of 0.2 mm. In these experiments a continuous-wave argon ion laser was used as an excitation source. The laser radiation was coupled into a microscope and into the micromixer covered with a quartz plate. A special microscope objective was used. It allows the correction of optical aberrations resulting from quartz plates up to a thickness of 2 mm. Concentration profiles of acetal, methanol, and acetone were measured across the width of the microchannel.     

Was? Wie? Warum? Jugendliche erforschen Flusslandschaften – Förderung des Systemverständnisses als Basis für gelebte Partizipation im Flussgebietsmanagement

River landscape planning and management to promote the positive long-term development of river landscapes must adhere to the principle of sustainability. In this context, the goal is to initiate a development process for river landscapes that successfully reconciles the requirements of nature and water conservation with social and economic aspects, and which actively involves affected citizens in the decision-making process. A systems-based understanding and the opportunity to make ecologically relevant decisions are essential prerequisites for participative processes.     

Metronidazole resistance in Campylobacter jejuni from poultry meat

The occurrence of metronidazole resistance was investigated among Campylobacter jejuni in raw poultry meat collected from supermarkets. MICs were determined by the agar dilution procedure in the testing range of 3 to 60 microg/ml metronidazole. The MICs showed a bimodal distribution with a significant proportion of metronidazole-resistant isolates among C. jejuni from raw broiler and turkey meat. Metronidazole resistance occurred most frequently among turkey meat isolates (P < 0.005). This is the first report of foodborne bacteria carrying metronidazole resistance.     

Photo‐Crosslinked Elastomeric Bimodal Poly(trimethylene carbonate) Networks

Using methacrylated poly(trimethylene carbonate) oligomers unimodal (prepared from one macromer) and bimodal (prepared from two macromers with different molecular weights) photo‐crosslinked networks and structures are prepared by stereolithography. The obtained biodegradable networks are flexible and elastic. Compared to the corresponding unimodal networks, the tensile properties of bimodal poly(trimethylene carbonate) (PTMC) network films are significantly enhanced. Resilient materials with increased toughness and suture retention strengths are obtained. The mechanical properties of the bimodal networks compare favorably with those of unimodal networks prepared previously from PTMC macromers with much higher molecular weights. Tough porous PTMC structures with designed diamond pore network architectures can also be readily prepared by stereolithography. Upon swelling of these PTMC structures in a solvent, the pore sizes and pore size distribution increases while the porosity decreases.     

Rapid eye movement sleep time in dairy cows changes during the lactation cycle

The importance of rest and sleep is well established; we know, for example, that lack of sleep impairs immune function in rats and increases pain sensitivity in humans. However, little is known about sleep in dairy cows, but a lack of rest and sleep is discussed as a possible welfare problem in cattle. A first step toward a better understanding of sleep in dairy cows is to quantify the time cows spend awake and asleep in different stages of lactation. Using electrophysiological recordings on 7 occasions in wk ?2, 2, 7, 13, 22, 37, and 45 in relation to calving, we investigated changes in rapid eye movement (REM) sleep time as well as non-rapid eye movement (NREM) sleep, drowsing, awake, and rumination in 19 dairy cows of the Swedish Red breed kept in single pens with ad libitum access to feed and water. The recordings on wk ?2 and 45 were conducted during the dry period, and all others during lactation. The PROC MIXED procedure in SAS (SAS Institute Inc., Cary, NC) was used to test for significant differences in REM, NREM, drowsing, awake, and rumination between the different stages of lactation cycle. Pairwise comparisons between all recording occasions showed that total REM sleep duration was shorter for cows in wk 2 relative to calving compared with wk ?2, and the number of REM sleep bouts were fewer in wk 2 compared with wk ?2. The REM sleep was recorded during both the day (0500–2100 h) and night (2100–0500 h), but predominantly performed at night compared with daytime, and the bout duration was longer during nighttime compared with daytime. A tendency was observed for time spent in NREM sleep to be shorter in wk 2 relative to calving compared with wk ?2. The duration spent drowsing was shorter for cows in wk 2 and 13 relative to calving compared with wk ?2. We found no effect of stage of lactation cycle on the duration of awake or ruminating. Our study is the first to assess sleep distribution during a lactation cycle, and our results show that stage of lactation is important to consider when moving forward with sleep investigations in dairy cows. The shortest REM sleep duration was found for cows 2 wk after calving and longest 2 wk before calving, and the difference was due a higher number of REM sleep bouts in the recording 2 wk before calving. The REM sleep and rumination predominantly occurred at night but were recorded during both day and night.     

A standardized conjugation protocol to asses antibiotic resistance transfer between lactococcal species

Optimal conditions and a standardized method for conjugation between two model lactococcal strains, Lactococcus lactis SH4174 (pAMbeta1-containing, erythromycin resistant donor) and L. lactis Bu2-60 (plasmid-free, erythromycin sensitive recipient), were developed and tested in a inter-laboratory experiments involving five laboratories from different countries. The ultimate goal of the study was to assess the microbial potential of antibiotic resistance transfer among Lactic Acid Bacteria (LAB). The influence of culture age (various OD values) and ratios of donor and recipient cultures as well as filter, solid and liquid mating techniques, were examined in order to optimize the conjugation protocol. In the result of these studies, we concluded that the donor-to-recipient ratio appear to be important; the most efficient technique for conjugation was filter mating and the optimal conditions for gene transfer were observed when late logarithmic cultures of both donor and recipient were used. Comparison of conjugal transfer frequencies between five partner laboratories showed that results are sufficiently intra-laboratory repeatable and inter-laboratory comparable. This is the first study of this kind, in which a standardized protocol of conjugal mating for testing antibiotic resistance dissemination among LAB was established and validated.     

On Rollin: Rational ethics?

Argues that B. E. Rollin's (see record 1986-11050-001) article on the moral status of research animals in psychology appears to advance the agenda of linking morality with cognitive psychology and immorality with behaviorism and that Rollin's statement that moral questions can be approached and decided in a rational and dispassionate manner is not supported by his subsequent discussion. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Novel hyperbranched glycomimetics recognized by the human mannose receptor: quinic or shikimic acid derivatives as mannose bioisosteres

The mannose receptor mediates the internalization of a wide range of molecules or microorganisms in a pattern recognition manner. Therefore, it represents an attractive entry for specific drug, gene, or antigen delivery to macrophages and dendritic cells. In an attempt to design novel effective synthetic mannose receptor ligands, quinic and shikimic acid were selected as putative mannose mimics on the basis of X-ray crystallographic data from the related rat mannose-binding lectin. As the mannose receptor preferentially binds to molecules displaying several sugar residues, fluorescein-labeled cluster quinic and shikimic acid derivatives with valencies of two to eight were synthesized. Their mannose receptor mediated uptake was assayed on monocyte-derived human dendritic cells by cytofluorimetric analysis. Mannose-receptor specificity was further assessed by competitive inhibition assays with mannan, by confocal microscopy analysis, and by expression of the mannose receptor in transfected Cos-1 cells. Constructs derived from both quinic and shikimic acid were efficiently recognized by the mannose receptor with an optimum affinity for the molecules with a valency of four. As a result, commercially available quinic and shikimic acids appear as stable mannose bioisosteres, which should prove valuable tools for specific cell delivery.