Osmoregulation and acid-base tolerance in fish

The gill, with a large surface area in intimate contact with the environment, is the primary organ of ion and acid-base regulation in fish. These same characteristics make the gill epithelium particularly susceptible to a number of environmental perturbations, including osmotic challenges and metabolic acidosis. For most freshwater fish, the active uptake of the strong ions, sodium and chloride, are intimately linked with the excretion of acid and base equivalents, respectively. However, fish from the genus Fundulus, are unique in their apparent lack of active chloride uptake at the gills. This unique feature makes limiting Cl- loss through paracellular pathways the only practical strategy for these species in tolerating acute exposure to hypoosmotic conditions especially when dietary chloride is limited. We find that Fundulus grandis can dynamically regulate their paracellular pathway in the gill epithelium at salinities approaching fresh water. We observe the significant up-regulation in the mRNA levels of several claudins in the gill and that some of these claudinsexhibit expressional discrepancies between mitochondrion-rich and pavement cells in fish gills, which shows correlations with changes in gill morphology and ion flux rates in fish. Collectively, our data suggest that claudins may play important roles in regulating ion flux across paracellular pathways of Fundulus during osmotic challenges. The linkage between osmoregulation and acid-base tolerance has long been studied in teleost fish. Failure to identify an active Cl- uptake system in freshwater Fundulusindicates the uniqueness of these species in osmoregulation and acid-base tolerance. We find that Fundulus heteroclitus increases Na+ uptake within the first few hours of metabolic acidosis,We also find that metabolic acidosis induces the changes of mRNA levels of several gill claudin proteins, which may play roles in regulating the permeability of the paracellular pathway to strong ions. Our data show Fundulus heteroclitus is capable to cope with great metabolic acidosis within their bodies, which may contribute to their adaptation to internal and external perturbations

Performance Evaluation for the Sustainable Supply Chain Management

Supply chain SC activities transform natural resources, raw materials, and components into various finished products that are delivered to end customers. A high efficient SC would bring great benefits to an enterprise such as integrated resources, reduced logistics costs, improved logistics efficiency, and high quality of overall level of services. In contrast, an inefficient SC will bring additional transaction costs, information management costs, and resource waste, reduce the production capacity of all enterprises on the chain, and unsatisfactory customer relationships. So the evaluation of a SC is important for an enterprise to survive in a competitive market in a globalized business environment. Therefore, it is important to research the various methods, performance indicator systems, and technology for evaluating, monitoring, predicting, and optimizing the performance of a SC. A typical procedure of the performance evaluation (PE) of a SC is to use the established evaluation performance indicators, employ an analytical method, follow a given procedure, to carry out quantitatively or qualitatively comparative analysis to provide the objective and accurate evaluation of a SC performance in a selected operation period. Various research works have been carried out in proposing the performance indicator systems and methods for SC performance evaluations. But there are no widely accepted indicator systems that can be applied in practical SC performance evaluations due to the fact that the indicators in different systems have been defined without a common understanding of the meanings and the relationships between them, and they are nonlinear and very complicated

On the security of the Yen-Guo's domino signal encryption algorithm (DSEA)

Recently, a new domino signal encryption algorithm (DSEA) was proposed for digital signal transmission, especially for digital images and videos. This paper analyzes the security of DSEA, and points out the following weaknesses: 1) its security against the brute-force attack was overestimated; 2) it is not sufficiently secure against ciphertext-only attacks, and only one ciphertext is enough to get some information about the plaintext and to break the value of a sub-key; 3) it is insecure against known/chosen-plaintext attacks, in the sense that the secret key can be recovered from a number of continuous bytes of only one known/chosen plaintext and the corresponding ciphertext. Experimental results are given to show the performance of the proposed attacks, and some countermeasures are discussed to improve DSEA.Comment: 11 pages, 5 figure

Web Portals in SMEs – Two Case Studies

This paper examines how two small to medium sized enterprises (SMEs) implemented web portals as part of a new ebusiness strategy to underpin future corporate expansion. The first company (Unified Office Products Limited) transformed itself from a traditional office supplies company into an intermediary trading over the web with a range of business partners in the office supplies supply chain. In the second case study, a small consultancy and training organisation (C&G Services Europe Ltd) saw the opportunity to develop a web portal to improve its on-line service to key customers, including some of the major utilities companies in the UK. Both these projects were implemented via the Knowledge Transfer Partnership scheme that provides UK Government funding to support university employed project managers working in industry to lead projects of key value to the partner companies. The progress of both companies across the duration of these projects is gauged against two mainstream models of IT and ebusiness development