GENERALIZATION OF PROXY SIGNATURE BASED ON FACTORIZATION

A rich set of proxy signature schemes have been widely researched and discussed so far. However, they have been mainly focusing on dealing with one or two separate proxy situations each. In this article, the authors proposed the generalization of the (t(1)/n(1) - t(2)/n(2)) proxy signature scheme based on the factorization of the square root modulo of a composite number. This scheme can be applied to every proxy situation. The (t(1)/n(1) - t(2)/n(2)) proxy signature scheme allows the original group of original signers to delegate their signing capability to a designated proxy group of proxy signers. Any verifier can verify the proxy signatures on the messages with the knowledge of the identities of the actual original signers and the actual proxy signers. Furthermore, all possible attacks that have been analyzed so far have failed to break the proposed scheme

Ethanol modified supercritical fluids extraction of scopoletin and artemisinin from Artemisia annua L

This work studied the supercritical carbon dioxide (SC-CO2) extractions with adding 16.25% ethyl alcohol as a co-solvent to obtain scopoletin and artemisinin from Artemisia annua L. A two-factor central composite experimental design was adopted to determine the optimal operation conditions in extracting the maximal amount of these bioactive compounds. Experimental results indicated that the 289 mu g of scopoletin/g of the feed in dry basis and the 11.6 mg of artemisinin/g of the feed had been obtained at these optimal conditions. Two hours ethanol modified SC-CO2 extractions were superior to 16 h Soxhlet N-hexane extractions in producing more pure artemisinin and scopoletin and the amount of the extracts increased with the density of SC-CO2. A normal phase silica-gel column chromatography to purify artemisinin from the SC-CO2 extract presented that the purity of artemisinin attained 98.2% but with a low recovery of 54.4%. This reduced recovery may be caused by an occurrence of the bridging peroxide atoms of artemisinin reacted with silica-gel molecules during the column purification. (c) 2007 Elsevier B.V. All rights reserved

Field emission properties of carbon nanotube cathodes produced using composite plating

Field emission properties of carbon nanotube field emission cathodes (CNT-FECs) produced using composite plating are studied. The experiment uses a CNT suspension and electroless Ni plating bath to carry out composite plating. The CNTs were first purified by an acid solution, dispersed in a Ni electrobath, and finally co-deposited with Ni on glass substrates to synthesize electrically conductive films. Field emission scanning electron microscopy and Raman spectroscopy results show that the field emission characteristics and graphitic properties of CNT-FECs depend on the pH value of the electrobath. Experiments show that the optimum electrobath pH value is 5.4, achieving a field emission current density of 1.0mA/cm(2) at an applied electric field of 1.5V/mu m. The proposed CNT-FECs possess good field emission characteristics and have potential for backlight unit application in liquid crystal displays. (C) 2010 Elsevier B.V. All rights reserved

A legionellosis case due to contaminated spa water and confirmed by genomic identification in Taiwan

Tracing the source of a legionellosis (LG) case revealed that the Legionella pneumophila (LP) strain isolated from patient's sputum shared the same serogroup (SG) and PFGE-type with 4 LP strains obtained from a spa center. With a high LP-contamination rate (81.2%, 13/16) in all of its 16 basins, this spa center was also found to have a multi-genotypic distribution among its 13 LP isolates, which can be categorized into 5 PFGE-types. Despite such a serious contamination in the spa center, which usually had ca. 100 visitors per day, this male patient, bearing LG-risk factors of long-term heavy smoking and alcoholism, was the only case identifiable after an active investigation. To explore the possible reason for this sporadic infection, all 5 PFGE-types of LP isolated were assayed for their presence of two important virulent genes (lvh and rtxA) and were identified as either less-virulent (Ivh(+), rtrA(-)) or non-virulent (lvh(-), rtxA(-)) types. The strong virulent type (lvh(+), rtxA(+)) usually seen in clinical strains elsewhere was not found here. Moreover, the LG-causative type in this infection was the only one to be classified as the less-virulent type, with the presence of lvh gene indicating its relatively more virulent potential than other 4 PFGE-types. Accordingly, mutual interaction between LP's virulent potential and patient's health-status was suggested to be the force directing the opportunistic infection of this sporadic case. This is the first spa-associated infection caused by SG 2 of LP

Comparison of photocatalytic activities of various dye-modified TiO2 thin films under visible light

Owing to the large band gap energy of 3.2eV, pure TiO2 film operates as an efficient photocatalyst under UV light irradiation and exhibits no photocatalytic activity under the visible spectral region. UV is only about 3% of the light existing in the solar spectrum. Currently, the red-shift in the band gap energy induced by dye-modified TiO2 film is one of the most popular and economic processes for improving the drawback in TiO2 photocatalyst. Therefore, we assess the photocatalytic efficiency of dye-modified TiO2 thin film using various dye molecules such as Eosin Y, Safranine O and tris-2, 2'-bipyridyl dichlororuthenium (II) hexahydrate (Rubpy) using the sol-gel process under visible light (lambda>400 nm). These results showed that TiO2 thin film modified with Safranine O dye had the best photodegrading efficiency under visible light irradiation. The photocatalytic inactivation of Safranine O and Eosin Y dye-modified TiO2 thin films against phytopathogenic bacteria including Enterobacter cloacae SM1 and Erwinia carotovara subsp. carotovora 3 which cause severe soft/basal rot disease in vegetable crops in Taiwan were all more than 90% after irradiation with visible light for 60min. The evidence suggests that the dye-modified TiO2 thin film under visible light irradiation has potential for plant protection applications in hydroponic systems. (C) 2008 Elsevier B.V. All rights reserved