Deletion of toxin–antitoxin systems in the evolution of Shigella sonnei as a host-adapted pathogen

Pathogenic Shigella spp. are the leading cause of bacterial dysentery, with Shigella flexneri and Shigella sonnei accounting for around 90% of cases worldwide. While S. flexneri causes most disease in low-income countries (following ingestion of contaminated food and/or water), S. sonnei predominates in wealthy countries and is mainly spread from person to person. Although both species contain a large virulence plasmid, pINV, that is essential for the organism to cause disease, little is known about its maintenance. Here, using a counterselectable marker within the virulence-encoding region of pINV, we show that the S. sonnei plasmid is less stable than that of S. flexneri, especially at environmental temperatures. GmvAT, a toxin–antitoxin system, is responsible for the difference in stability and is present in pINV from S. flexneri but absent in S. sonnei pINV; GmvT is an acetyltransferase toxin that inhibits protein translation. Loss of GmvAT and a second toxin–antitoxin system, CcdAB, from pINV reduces S. sonnei plasmid stability outside the host, reflecting the host-adapted lifestyle and person-to-person transmission of this species, and hence the striking differences in its epidemiology

Intravenous bolus somatostatin after diagnostic cholangiopancreatography reduces the incidence of pancreatitis associated with therapeutic endoscopic retrograde cholangiopancreatography procedures: A randomised controlled trial

Background: Previous studies suggested that somatostatin given before endoscopic retrograde cholangiopancreatography (ERCP) may reduce the incidence of post-ERCP pancreatitis. However, the routine use of somatostatin in all patients undergoing ERCP is not likely to be cost effective. This study evaluated whether intravenous bolus somatostatin given after diagnostic cholangiopancreatography could reduce the incidence of pancreatitis in a group of patients undergoing therapeutic ERCP procedures. Methods: In a randomised, double blind, controlled trial, the effect of intravenous bolus somatostatin 250 μg given immediately after diagnostic cholangiopancreatography was compared with that of placebo in patients who required endoscopic sphincterotomy or other therapeutic procedures. The primary end point was the incidence of post-ERCP clinical pancreatitis, and a secondary end point was the incidence of hyperamylasemia. Results: A total of 270 patients were randomised. The somatostatin group (n = 135) and the placebo group (n = 135) were comparable in age, sex, indications for treatment, and types of procedure. The frequencies of clinical pancreatitis (4.4% v 13.3%; p = 0.010) and hyperamylasemia (26.0% v 38.5%; p = 0.036) were both significantly lower in the somatostatin group compared with the placebo group. Conclusions: A single dose of intravenous bolus somatostatin, given immediately after diagnostic cholangiopancreatography, is effective in reducing the incidence of pancreatitis after therapeutic ERCP. This novel approach of administering prophylactic somatostatin may offer a cost effective prophylaxis for post-ERCP pancreatitis.published_or_final_versio

Medical treatment of viral pneumonia including SARS in immunocompetent adult

Since no randomized controlled trials have been conducted on the treatment of viral pneumonia by antivirals or immunomodulators in immunocompetent adults, a review of such anecdotal experience are needed for the more rational use of such agents. Case reports (single or case series) with details on their treatment and outcome in the English literature can be reviewed for pneumonia caused by human or avian influenza A virus (50 patients), varicella zoster virus (120), adenovirus (29), hantavirus (100) and SARS coronavirus (SARS-CoV) (841). Even with steroid therapy alone, the mortality rate appeared to be lower when compared with conservative treatment for pneumonia caused by human influenza virus (12.5% vs. 42.1%) and hantavirus (13.3% vs. 63.4%). Combination of an effective antiviral, acyclovir, with steroid in the treatment of varicella zoster virus may be associated with a lower mortality than acyclovir alone (0% vs. 10.3%). Combination of interferon alfacon-1 plus steroid, or lopinavir/ritonavir, ribavirin plus steroid were associated with a better outcome than ribavirin plus steroid (0% vs. 2.3% vs. 7.7%, respectively). Combination of lopinavir/ritonavir plus ribavirin significantly reduced the virus load of SARS-CoV in nasopharyngeal, serum, stool and urine specimens taken between day 10 and 15 after symptom onset when compared with the historical control group treated with ribavirin. It appears that the combination of an effective antiviral and steroid was associated with a better outcome. Randomized therapeutic trial should be conducted to ascertain the relative usefulness of antiviral alone or in combination with steroid. © 2004 The British Society. Published by Elsevier Ltd. All rights reserved.postprin

Optically and electrically tunable graphene quantum dot–polyaniline composite films

Graphene quantum dot-polyaniline (PANI-GQD) composite films were synthesized by a chemical oxidation polymerization process. The optical properties of the PANI-GQD composite were studied by varying the mole concentration of PANI and the size of the GQDs. The Au/PANI-GQDs/ITO sandwich device was fabricated in order to investigate the transport properties of the composite. A stable hysteresis loop was observed in response to the applied voltage. By varying the PANI content and size of the GQDs, the area within the hysteresis loop and electrical conductance behavior of the device can be tuned in a controlled manner. Both the tunable luminescence and electrical hysteresis behavior are attributed to surface states of the GQDs. The PANI-GQD composite films are expected to find application in photonic devices.Department of Applied Physic

High-Performance Pentacene Thin-Film Transistor With High-κ HfLaON as Gate Dielectric

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High-mobility pentacene OTFT with TaLaO gate dielectric passivated by fluorine plasma

Pentacene thin-film transistor with high-κ TaLaO as gate dielectric has been fabricated and shows a carrier mobility of 0.73 cm2/V s, much higher than that based on pure La2O3 (0.43 cm2/V s) due to the smoother surface of the TaLaO film and thus larger pentacene islands grown on it in the initial stage. Moreover, among various times for fluorine-plasma treatment on the TaLaO gate dielectric, 100 seconds result in the highest carrier mobility of 1.12 cm2/V s due to (1) smoothest oxide surface achieved by fluorine passivation of oxide traps, as measured by AFM and supported by smallest sub-threshold swing and lowest low-frequency noise; (2) the largest pentacene grains grown on the smoothest oxide surface, as demonstrated by AFM. Pentacene islands on on TaLaO or La2O3 gate dielectric with different plasma treatment times.postprin

High-mobility pentacene thin-film transistor by using LaxTa(1-x)Oy as gate dielectric

Pentacene organic thin-film transistors (OTFTs) using LaxTa(1−x)Oy as gate dielectric with different La contents (x = 0.227, 0.562, 0.764, 0.883) have been fabricated and compared with those using Ta oxide or La oxide. The OTFT with La0.764Ta0.236Oy can achieve a carrier mobility of 1.21 cm2 V−1s−1s, which is about 40 times and two times higher than those of the devices using Ta oxide and La oxide, respectively. As supported by XPS, AFM and noise measurement, the reasons lie in that La incorporation can suppress the formation of oxygen vacancies in Ta oxide, and Ta content can alleviate the hygroscopicity of La oxide, resulting in more passivated and smoother dielectric surface and thus larger pentacene grains, which lead to higher carrier mobility.postprin

Effects of fluorine plasma and ammonia annealing on pentacene thin-film transistor with HfTiO as gate dielectric

Pentacene organic thin-film transistor (OTFT) with high-K HffiO gate dielectric has been fabricated. The effects of fluorine plasma and ammonia annealing on the properties of the OTFT have been studied. After treating the dielectric in the plasma, the carrier mobility of the transistor can be improved by about 5 times to 0.0883 cm2/V•s. Moreover, the fluorine plasma treatment can shift the threshold voltage of the device in the positive direction. Experimental results also show that NH3 annealing can enhance the OTFT performance in terms of higher mobility, smaller sub-threshold slope and larger on/off ratio.published_or_final_versio

Improved performance for OTFT with HfTiO2 as gate dielectric by N2O annealing

OTFTs with HfTiO 2 as gate dielectric have been successfully fabricated. The devices show small threshold voltage and subthreshold slope, and thus are suitable for low-voltage and low-power applications. This work also finds that OTFT with gate dielectric annealed in N 2O has larger dielectric constant, smaller threshold voltage, smaller subthreshold slope and larger on/off ratio than the N 2-annealed sample. This demonstrates that the N 2O annealing is an important surface treatment for preparing a high-quality insulator/organic interface. © 2007 IEEE.published_or_final_versio

The spatial and temporal distribution of heavy metals in sediments of Victoria Harbour, Hong Kong

Author name used in this publication: Chloe Wing-yee TangAuthor name used in this publication: Carman Ching-man Ip2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe