A multipath ad hoc routing approach to combat wireless link insecurity

As wireless LAN (WLAN) technologies proliferate, it is becoming common that ad hoc networks, in which mobile devices communicate via temporary links, are built using WLAN products. In the IEEE 802.11b standard, the Wired Equivalent Privacy (WEP) scheme is used as the only measure to enhance data confidentiality against eavesdropping. However, owing to the well known pitfalls in Initialization Vector (IV) attachment in the ciphertext, the underlying 40-bit RC4 encryption mechanism in WEP is unsafe regardless of the key size. On the other hand, solutions involving replacement of RC4 by another cipher are not attractive because that may lead to reconstruction of the whole system and result in high costs as well as redevelopment of the products. In order to enhance the security on the existing development efforts, we propose a novel multipath routing approach to combat the link insecurity problem at a higher protocol layer. This approach does not require the application to use sophisticated encryption technologies that may be too heavy burdens for mobile devices. Based on our suggested confidentiality measurement model, we find that our proposed multipath ad hoc routing technique, called Secure Multipath Source Routing (SMSR), is highly effective.published_or_final_versio

Follow up of serial urea breath test results in patients after consumption of antibiotics for non-gastric infections

Aim: The widespread use of antibacterial therapy has been suggested to be the cause for the decline in the prevalence of Helicobacter pylori infection. This study examine the serial changes of urea breath test results in a group of hospitalized patients who were given antibacterial therapy for non-gastric infections. Methods: Thirty-five hospitalized patients who were given antibacterial therapy for clinical infections, predominantly chest and urinary infections, were studied. Most (91 %) patients were given single antibiotic of either a penicillin or cephalosporin group. Serial 13C-urea breath tests were performed within 24 hours of initiation of antibiotics, at one-week and at six-week post-therapy. H. pylori infection was diagnosed when one or more urea breath tests was positive. Results: All 35 patients completed three serial urea breath tests and 26 (74 %) were H. pylori-positive. Ten (38 %) H. pylori-infected patients had at least one negative breath test results during the study period. The medium delta 13C values were significantly lower at baseline (8.8) than at one-week (20.3) and six-week (24.5) post-treatment in H. pylori-positive individuals (P=0.022). Clearance of H. pylori at six-week was only seen in one patient who had received anti-helicobacter therapy from another source. Conclusion: Our results suggested that one-third of H. pylori-infected individuals had transient false-negative urea breath test results during treatment with antibacterial agent. However, clearance of H. pylori infection by regular antibiotic consumption is rare.published_or_final_versio

Isolation of Helicobacter pylori from vomitus in children and its implication in gastro-oral transmission

OBJECTIVE: The route of transmission of Helicobacter pylori (H. pylori) is unclear. Gastro-oral transmission via contaminated vomitus has been proposed as an important mode of transmitting H. pylori, especially in children. This pilot study attempted to isolate H. pylori from the vomitus of children. METHODS: Children presenting for evaluation with gastroenteritis- associated vomiting were studied. Fresh vomitus samples were collected for detection of H. pylori by bacteriological culture and polymerase chain reaction (PCR). A rapid, whole blood test was used to determine the H. pylori status of patients. RESULTS: A total of 18 children with mean age of 6 yr were studied; four had a positive serology test. Among these four children, H. pylori was isolated from vomitus by culture in one child and by PCR in two. An 18-month-old girl with negative serology had H. pylori detected in vomitus by PCR. Six months later, she had seroconversion confirmed, suggesting that she had an acute H. pylori infection on initial presentation. CONCLUSIONS: This is the first study reporting successful isolation of H. pylori from naturally produced vomitus. The result implies that transmission of H. pylori infection by vomitus, especially in children, is possible.link_to_subscribed_fulltex