Meeting Standards for Lead in Drinking Water

During the last twenty years, the UK has made steady progress in the understanding of the 'lead in drinking water'issue and towards compliance with a lead standard which is more stringent than elsewhere in Europe.
Evaluating the needs for corrective action has not been straightforward because of the difficulties in characterizing the pick-up of lead from lead pipes throughout whole water supply zones. Survey methods have developed over the past twenty years as the behaviour of lead pipes has become better understood, but some ambiguities may still need to be addressed.
Information from Bristol Water suggests that compliance with a new lead standard of 10 μg/1 may be feasible by corrective water treatment in some zones, based on the already accepted practice of dosing with phosphoric acid, depending on how this more stringent standard is implemented. This view is also held by Anglian Water, based on their extensive experience with phosphoric acid dosing (without any significant problems) since the mid-1980s. Therefore total lead pipe replacement, at substantially higher cost, can likely be avoided in many zones.     

Apical sorting of bovine enteropeptidase does not involve detergent-resistant association with sphingolipid-cholesterol rafts

Enteropeptidase is a heterodimeric type II membrane protein of the brush border of duodenal enterocytes. In this location, enteropeptidase cleaves and activates trypsinogen, thereby initiating the activation of other intestinal digestive enzymes. Recombinant bovine enteropeptidase was sorted directly to the apical surface of polarized Madin-Darby canine kidney cells. Replacement of the cytoplasmic and signal anchor domains with a cleavable signal peptide (mutant proenteropeptidase lacking the amino-terminal signal anchor domain (dSA-BEK)) caused apical secretion. The additional amino-terminal deletion of a mucin-like domain (HL-BEK) resulted in secretion both apically and basolaterally. Further deletion of the noncatalytic heavy chain (L-BEK) resulted in apical secretion. Thus enteropeptidase appears to have at least three distinct sorting signals as follows: the light chain (L-BEK) directs apical sorting, addition of most of the heavy chain (HL-BEK) inhibits apical sorting, and addition of the mucin-like domain (dSA-BEK) restores apical sorting. Inhibition of N-linked glycosylation with tunicamycin or disruption of microtubules with colchicine caused L-BEK to be secreted equally into apical and basolateral compartments, whereas brefeldin A caused basolateral secretion of L-BEK. Full-length BEK was not found in detergent-resistant raft domains of Madin-Darby canine kidney cells or baby hamster kidney cells. These results suggest apical sorting of enteropeptidase depends on N-linked glycosylation of the serine protease domain and an amino-terminal segment that includes an O-glycosylated mucin-like domain and three potential N-glycosylation sites. In contrast to many apically targeted proteins, enteropeptidase does not form detergent-resistant associations with sphingolipid-cholesterol rafts.     

Comparing six video chat tools: A critical evaluation by language teachers

This article presents a critical comparison of the usefulness and practicality of six CMC video chat tools (CUworld, ICQ, MSN Messenger, Paltalk, Skype, and Yahoo Messenger) from the perspective of language teaching professionals. This comparison is based on the results of a semester-long project between graduate students at an American university and their counterparts at a university in Turkey. The language teachers were asked to pair up with a partner in the collaborating university to test and then evaluate each of these tools via video chat tool evaluation sheets. They also completed an overall evaluation sheet commenting on CMC tools in general and ranking the video chat tools in terms of their potential as language teaching tools and their usability for personal communication purposes. The qualitative and quantitative analyses of the evaluation sheets indicate a clear preference for MSN Messenger and Skype while placing CUworld and Paltalk at the bottom of the list. The article also provides pedagogical implications and applications for using tools for language teaching purposes.     

A Tandem Enzymatic sp2‐C‐Methylation Process: Coupling in Situ S‐Adenosyl‐l‐Methionine Formation with Methyl Transfer

A one‐pot, two‐step biocatalytic platform for the regiospecfic C‐methylation and C‐ethylation of aromatic substrates is described. The tandem process utilises SalL (Salinospora tropica) for in situ synthesis of S‐adenosyl‐l ‐methionine (SAM), followed by alkylation of aromatic substrates by the C‐methyltransferase NovO (Streptomyces spheroides). The application of this methodology is demonstrated for the regiospecific labelling of aromatic substrates by the transfer of methyl, ethyl and isotopically labelled ¹³CH_3, ¹³CD₃ and CD₃ groups from their corresponding SAM analogues formed in situ.     

Human Serum Transferrin Fibrils: Nanomineralisation in Bacteria and Destruction of Red Blood Cells

Fibrils formed by human serum transferrin [(1–3 μM ) apo‐Tf, partially iron‐saturated (Fe_0.6‐Tf) and holo‐Tf (Fe₂‐Tf) forms], from dilute bicarbonate solutions, were deposited on formvar surfaces and studied by electron microscopy. We observed that possible bacterial contamination appears to give rise to long, pea‐pod‐like (PPL) structures for Fe₂‐Tf, attributable to the formation of polyhydroxybutyrate (PHB) storage granules, under the nutrient‐limiting conditions used. These PPL structures contained periodic nanomineralisation sites susceptible to uranyl stain. Extended incubation of transferrin solutions (about four days) gave rise to extensive transferrin fibril structures. Optical microscopy and AFM studies showed that red blood cells (RBCs) readily adhere to these fibrils. Moreover, the fibrils appear to penetrate RBC membranes and to induce rapid cell destruction (within about 5 h). It is speculated that in situations in vivo where transferrin fibrils can form, such interactions might have adverse physiological consequences, and further studies could aid the understanding of related pathological events.     

Influence of high‐pressure processing on selected polymeric materials and on the migration of a pressure‐transmitting fluid

This study investigated the migration of 1,2‐propanediol (PG) through selected food packaging films exposed to high‐pressure processing (HPP). Pouches made from these materials were filled with 95% ethanol as a food‐simulating liquid. These packages were then processed using a pilot‐scale high‐pressure food processor at 400, 600 and 827 MPa and 30, 50 and 75°C for 10 min. Controls were processed at similar temperatures and times, but at atmospheric pressure. To investigate any structural changes to these films during HPP, water was used as the food simulant at temperatures of 30, 75, 85, 90 and 95°C and at pressures of 200, 400, 690 and 827 MPa. No detectable PG migration into the polyester/nylon/aluminium (Al) polypropylene (PP) meal‐ready‐to eat (MRE)‐type pouches was observed. PG migration into the nylon/ethylene vinyl alcohol (EVOH)/PE (EVOH) pouches was similar at 30, 50 and 75°C after 10 min under atmospheric pressure. However, PG migration into the EVOH pouches significantly decreased when treated with high pressure at 30, 50 and 75°C. At 75 and 50°C, the PG migration was significantly higher than the amounts detected at 30°C. Visible signs of delamination between the polypropylene (PP) and aluminum (Al) layers were observed in the MRE pouches processed at ≥200 MPa and 90°C for 10 min. This delamination appeared to occur between the PP and Al layers. The differential scanning calorimetric analyses and Fourier transform infrared (FTIR) spectra were similar for the high‐pressure treated pouches when compared to their respective controls. This indicated that there were no HPP‐induced molecular changes to the treated pouches. Results from this study should be useful to HPP users for predicting PG migration trends and in deciding the selection of appropriate packaging materials for use under similar processing conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

A comprehensive study of modal characteristics of a cylindrical manipulator with both link and joint flexibility

A thorough understanding of modal characteristics of vibrating manipulators is essential for improved dynamic positioning accuracy. Presented in this work is an extensive investigation of a cylindrical manipulator, consisting of a revolute and a prismatic joint. In general, for high-speed, flexible manipulators, modal properties depend mainly upon the following factors: (1) physical dimensions and material properties of components (such as arms and joints), which remain unchanged for a chosen manipulator; (2) a manipulator's position (or orientation) as a result of joint actuations; (3) the rigid-elastic coupling effect; and (4) the centrifugal stiffening effect due to the influence of internal axial force on the lateral stiffness. This work is intended to study the effects of each of the above factors on modal characteristics of the manipulator, and gives insight into the susceptibility of the modal parameters to each factor. In addition, joint flexibility has substantial influence on modal properties of a robotic system, depending on the relative importance of joint torsional stiffness to the stiffness of other members, such as the bending stiffness of arms. In the situation where the manipulator moves at a high speed, both rigid-elastic coupling and centrifugal stiffening effects can become important.     

Bounds on SIMO and MIMO Channel Estimation and Equalization with Side Information

Constrained Cramér-Rao bounds are developed for convolutive multi-input multi-output (MIMO) channel and source estimation in additive Gaussian noise. Properties of the MIMO Fisher information matrix (FIM) are studied, and we develop the maximum rank of the unconstrained FIM and provide necessary conditions for the FIM to achieve full rank. Equality constraints on channel and signal parameters provide a means to study the potential value of side information, such as training symbols (semi-blind case), constant modulus (CM) sources, or known channels. Nonredundant constraints may be combined in an arbitrary fashion, so that side information may be different for different sources. The bounds are useful for evaluating the performance of SIMO and MIMO channel estimation and equalization algorithms. We present examples using the constant modulus blind equalization algorithm. The constrained bounds are also useful for evaluating the relative value of different types of side information, and we present examples comparing semi-blind, constant modulus, and known channel constraints. While the examples presented are primarily in the communications context, the CRB framework applies generally to convolutive source separation problems.