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Exposure to hazardous volatile organic compounds, PM 10 and CO while walking along streets in urban Guangzhou, China
Toxic air pollutants in street canyons are important issues concerning public health especially in some large Asian cities like Guangzhou. In 1998 <18% of Guangzhou citizens used public transportation modes, with a majority commuting on foot (42%) or by bicycle (22%). Of the pedestrians, 57% were either senior citizens or students. In the present study, we measured toxic air pollutants while walking along urban streets in Guangzhou to evaluate pedestrian exposure. Volatile organic compounds (VOCs) were collected with sorbent tubes, and PM 10 and CO were measured simultaneously with portable analyzers. Our results showed that pedestrian exposure to PM 10 (with an average of 303 Όg m -3 for all samples) and some toxic VOCs (for example, benzene) was relatively high. Monocyclic aromatic hydrocarbons were found to be the most abundant VOCs, and 71% of the samples had benzene levels higher than 30 Όg m -3. Benzene, PM 10 and CO in walk-only streets were significantly lower (p<0.05) than in traffic streets, and the differences in exposure levels between new urban streets and old urban streets were highly significant (p<0.01). Pedestrian exposure to toxic VOCs and PM 10 was higher than those reported in other public transportation modes (bus and subway). The good correlations between BTEX, PM 10 and CO in the streets indicated that automotive emission might be their major source. Our study also showed that the risk to pedestrians due to air pollution was misinterpreted by the reported air quality index based on measurement of SO 2, NO x and PM 10 in the government monitoring stations. An urban roadside monitoring station might be needed by air quality monitoring networks in large Asian cities like Guangzhou, in order to survey exposure to air toxics in urban roadside microenvironments. © 2004 Elsevier Ltd. All rights reserved
Beat-to-beat ambulatory blood pressure estimation based on random forest
Ambulatory blood pressure is critical in predicting some major cardiovascular events; therefore, cuff-less and noninvasive beat-to-beat ambulatory blood pressure measure-ment is of great significance. Machine-learning methods have shown the potential to derive the relationship between physio-logical signal features and ABP. In this paper, we apply random forest method to systematically explorer the inherent connections between photoplethysmography signal, electrocardiogram signal and ambulatory blood pressure. To archive this goal, 18 features were extracted from PPG and ECG signals. Several models with most significant features as inputs and beat-to-beat ABP as outputs were trained and tested on data from the Multi-Parameter Intelligent Monitoring in Intensive Care II database. Results indicate that compared with the common pulse transit time method, the RF method gives a better performance for one-hour continuous estimation of diastolic blood pressure and systolic blood pressure under both the Association for the Advancement of Medical Instrumentation and British Hyper-tension Society standard
Antimicrobial activity of spherical silver nanoparticles prepared using a biocompatible macromolecular capping agent: evidence for induction of a greatly prolonged bacterial lag phase
<p>Abstract</p> <p>Background</p> <p>We have evaluated the antimicrobial properties of Ag-based nanoparticles (<it>Np</it>s) using two solid phase bioassays and found that 10-20 ÎŒL of 0.3-3 ÎŒM keratin-stabilized <it>Np</it>s (depending on the starting bacterial concentration = <it>C</it><sub>I</sub>) completely inhibited the growth of an equivalent volume of <it>ca</it>. 10<sup>3 </sup>to 10<sup>4 </sup>colony forming units per mL (CFU mL<sup>-1</sup>) <it>Staphylococcus aureus</it>, <it>Salmonella </it>Typhimurium, or <it>Escherichia coli </it>O157:H7 on solid surfaces. Even after one week at 37°C on solid media, no growth was observed. At lower <it>Np </it>concentrations (= [<it>Np</it>]s), visible colonies were observed but they eventually ceased growing.</p> <p>Results</p> <p>To further study the physiology of this growth inhibition, we repeated these experiments in liquid phase by observing microbial growth via optical density at 590 nm (OD) at 37°C in the presence of a [<it>Np</it>] = 0 to 10<sup>-6 </sup>M. To extract various growth parameters we fit all OD[t] data to a common sigmoidal function which provides measures of the beginning and final OD values, a first-order rate constant (<it>k</it>), as well as the time to calculated 1/2-maximal OD (<it>t</it><sub>m</sub>) which is a function of <it>C</it><sub>I</sub>, <it>k</it>, as well as the microbiological lag time (<it>T</it>).</p> <p>Performing such experiments using a 96-well microtitre plate reader, we found that growth <it>always </it>occurred in solution but <it>t</it><sub>m </sub>varied between 7 (controls; <it>C</it><sub>I </sub>= 8 Ă 10<sup>3 </sup>CFU mL<sup>-1</sup>) and > 20 hrs using either the citrate-([<it>Np</it>] ~ 3 Ă 10<sup>-7 </sup>M) or keratin-based ([<it>Np</it>] ~ 10<sup>-6 </sup>M) <it>Np</it>s and observed that {â<it>t</it><sub>m</sub>/â [<it>Np</it>]}<sub>citrate </sub>~ 5 Ă 10<sup>7 </sup>and {â<it>t</it><sub>m</sub>/â [<it>Np</it>]}<sub>keratin </sub>~ 10<sup>7 </sup>hr·L mol<sup>-1</sup>. We also found that there was little effect of <it>Np</it>s on <it>S. aureus </it>growth rates which varied only between <it>k </it>= 1.0 and 1.2 hr<sup>-1 </sup>(1.1 ± 0.075 hr<sup>-1</sup>). To test the idea that the <it>Np</it>s were changing the initial concentration (<it>C</it><sub>I</sub>) of bacteria (<it>i.e</it>., cell death), we performed probabilistic calculations assuming that the perturbations in <it>t</it><sub>m </sub>were due to <it>C</it><sub>I </sub>alone. We found that such large perturbations in <it>t</it><sub>m </sub>could only come about at a <it>C</it><sub>I </sub>where the probability of any growth at all was small. This result indicates that much of the <it>Np</it>-induced change in <it>t</it><sub>m </sub>was due to a greatly increased <it>T </it>(<it>e.g</it>., from <it>ca</it>. 1 to 15-20 hrs). For the solid phase assays we hypothesize that the bacteria eventually became non-culturable since they were inhibited from undergoing further cell division (<it>T </it>> many days).</p> <p>Conclusion</p> <p>We propose that the difference between the solid and liquid system relates to the obvious difference in the exposure, or residence, time of the <it>Np</it>s with respect to the bacterial cell membrane inasmuch as when small, <it>Np</it>-inhibited colonies were selected and streaked on fresh (<it>i.e</it>., no <it>Np</it>s present) media, growth proceeded normally: <it>e.g</it>., a small, growth-inhibited colony resulted in a plateful of typical <it>S. aureus </it>colonies when streaked on fresh, solid media.</p
Intermediate Trapping on a Mutant Retaining α-Galactosyltransferase Identifies an Unexpected Aspartate Residue *
Lipopolysaccharyl-alpha-1,4-galactosyltransferase C (LgtC), a glycosyltransferase family 8 alpha-1,4-galactosyltransferase from Neisseria meningitidis, catalyzes the transfer of galactose from UDP galactose to terminal lactose-containing acceptor sugars with net retention of anomeric configuration. To investigate the potential role of discrete nucleophilic catalysis suggested by the double displacement mechanism generally proposed for retaining glycosyltransferases, the side chain amide of Gln-189, which is suitably positioned to act as the catalytic nucleophile of LgtC, was substituted with the more nucleophilic carboxylate-containing side chain of glutamate in the hope of accumulating a glycosyl-enzyme intermediate. The resulting mutant was subjected to kinetic, mass spectrometric, and x-ray crystallographic analysis. Although the K(m) for UDP-galactose is not significantly altered, the k(cat) was reduced to 3% that of the wild type enzyme. Electrospray mass spectrometric analysis revealed that a steady state population of the Q189E variant contains a covalently bound galactosyl moiety. Liquid chromatographic/mass spectrometric analysis of fragmented proteolytic digests identified the site of labeling not as Glu-189 but, surprisingly, as the sequentially adjacent Asp-190. However, the side chain carboxylate of Asp-190 is located 8.9 A away from the donor substrate in the available crystal structure. Kinetic analysis of a D190N mutant at this position revealed a k(cat) value 3000-fold lower than that of the wild type enzyme. A 2.6-A crystal structure of the Q189E mutant with bound uridine 5'-diphospho-2-deoxy-2-fluoro-alpha-d-galactopyranose revealed no significant perturbation of the mode of donor sugar binding nor of active site configuration. This is the first trapping of an intermediate in the active site of a retaining glycosyltransferase and, although not conclusive, implicates Asp-190 as an alternative candidate catalytic nucleophile, thereby rekindling a longstanding mechanistic debate
Platinum nanoparticles on reduced graphene oxide as peroxidase mimetics for the colorimetric detection of specific DNA sequence
2015-2016 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Diarrhoea in critical care is rarely infective in origin, associated with increased length of stay and higher mortality
Diarrhoea, defined as > 3 loose or liquid stools per day, affects 9.7â41% of intensive care unit patients, negatively impacting on patient dignity, intensifying nursing workload and increasing morbidity. Its pathogenesis is poorly understood, but infective agents, intensive care unit therapies (such as enteral feed) and critical illness changes in the gut microbiome are thought to play a role. We analysed a consecutive cohort of 3737 patients admitted to a mixed general intensive care unit. Diarrhoea prevalence was lower than previously reported (5.3%), rarely infective in origin (6.5%) and associated with increased length of stay (median (inter-quartile range) 2.3 (1.0â5.0) days vs. 10 days (5.0â22.0), p < 0.001, sub-distribution hazard ratio 0.55 (95% CI 0.48â0.63), p < 0.001) and mortality (9.5% vs. 18.1%, p = 0.005, sub-distribution hazard ratio 1.20 (95% CI 0.79â1.81), p = 0.40), compared to patients without diarrhoea. In addition, 17.1% of patients received laxatives <24 h prior to diarrhoea onset. Further research on diarrhoea's pathogenesis in critical care is required; robust treatment protocols, investigation rationalisation and improved laxative prescribing may reduce its incidence and improve related outcomes
Measurement of the Branching Fraction of J/psi --> pi+ pi- pi0
Using 58 million J/psi and 14 million psi' decays obtained by the BESII
experiment, the branching fraction of J/psi --> pi+ pi- pi0 is determined. The
result is (2.10+/-0.12)X10^{-2}, which is significantly higher than previous
measurements.Comment: 9 pages, 8 figures, RevTex
First observation of psi(2S)-->K_S K_L
The decay psi(2S)-->K_S K_L is observed for the first time using psi(2S) data
collected with the Beijing Spectrometer (BESII) at the Beijing Electron
Positron Collider (BEPC); the branching ratio is determined to be
B(psi(2S)-->K_S K_L) = (5.24\pm 0.47 \pm 0.48)\times 10^{-5}. Compared with
J/psi-->K_S K_L, the psi(2S) branching ratio is enhanced relative to the
prediction of the perturbative QCD ``12%'' rule. The result, together with the
branching ratios of psi(2S) decays to other pseudoscalar meson pairs
(\pi^+\pi^- and K^+K^-), is used to investigate the relative phase between the
three-gluon and the one-photon annihilation amplitudes of psi(2S) decays.Comment: 5 pages, 4 figures, 2 tables, submitted to Phys. Rev. Let
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