1,322 research outputs found
Cost Effective Quality Assurance Practices in Highway Construction
The estimated value of the U.S. transportation infrastructure is over $7.0 trillion. The challenge is preserving the quality of the investment. State and federal departments of transportation have methods and procedures for best quality, but vary significantly. With the variations comes opportunity to assess the cost-effectiveness of different strategies and make recommendation on practices that are most successful.
A survey was created and sent to all 50 states and the District of Columbia. The survey was aimed to capture information on construction finished product testing methods, optimized/reduced sampling techniques, innovative QA practices that measure multiple performance criteria and QA processes that are rapid and cost effective.
There are many testing methods and procedures being used throughout the U.S. This thesis will allow state and federal transportation agencies to look at the findings and possibly implement them into their own agency with hopes of saving time and money for future projects
Current state of antimicrobial stewardship in children’s hospital emergency departments
BACKGROUND Antimicrobial stewardship programs (ASPs) effectively optimize antibiotic use for inpatients; however, the extent of emergency department (ED) involvement in ASPs has not been described. OBJECTIVE To determine current ED involvement in children's hospital ASPs and to assess beliefs and preferred methods of implementation for ED-based ASPs. METHODS A cross-sectional survey of 37 children's hospitals participating in the Sharing Antimicrobial Resistance Practices collaboration was conducted. Surveys were distributed to ASP leaders and ED medical directors at each institution. Items assessed included beliefs regarding ED antibiotic prescribing, ED prescribing resources, ASP methods used in the ED such as clinical decision support and clinical care guidelines, ED participation in ASP activities, and preferred methods for ED-based ASP implementation. RESULTS A total of 36 ASP leaders (97.3%) and 32 ED directors (86.5%) responded; the overall response rate was 91.9%. Most ASP leaders (97.8%) and ED directors (93.7%) agreed that creation of ED-based ASPs was necessary. ED resources for antibiotic prescribing were obtained via the Internet or electronic health records (EHRs) for 29 hospitals (81.3%). The main ASP activities for the ED included production of antibiograms (77.8%) and creation of clinical care guidelines for pneumonia (83.3%). The ED was represented on 3 hospital ASP committees (8.3%). No hospital ASPs actively monitored outpatient ED prescribing. Most ASP leaders (77.8%) and ED directors (81.3%) preferred implementation of ED-based ASPs using clinical decision support integrated into the EHR. CONCLUSIONS Although ED involvement in ASPs is limited, both ASP and ED leaders believe that ED-based ASPs are necessary. Many children's hospitals have the capability to implement ED-based ASPs via the preferred method: EHR clinical decision support. Infect Control Hosp Epidemiol 2017;38:469-475
Southern hemispheric halon trends and global halon emissions, 1978–2011
The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania, between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s, but those of H-1301 continue to increase up to mid-2011. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The observations suggest that the contribution of the halons to total tropospheric bromine at Cape Grim has begun to decline from a peak in 2008 of about 8.1 ppt. An extrapolation of halon mixing ratios to 2060, based on reported banks and predicted release factors, shows this decline becoming more rapid in the coming decades, with a contribution to total tropospheric bromine of about 3 ppt in 2060. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid-1990s, but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA (University of East Anglia) top-down model-derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). The implications of an alternative set of steady-state atmospheric lifetimes are discussed. Using a lifetime of 14 yr or less for H-1211 to calculate top-down emissions estimates would lead to small, or even negative, estimated banks given reported production data. Finally emissions of H-1202, a product of over-bromination during the production process of H-1211, have continued despite reported production of H-1211 ceasing in 2010. This raises questions as to the source of these H-1202 emissions
The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO2 oxidation : experiment, theory and modelling
The gas-phase reaction of alkenes with ozone is known to produce stabilised
Criegee intermediates (SCIs). These biradical/zwitterionic species have the
potential to act as atmospheric oxidants for trace pollutants such as
SO<sub>2</sub>, enhancing the formation of sulfate aerosol with impacts on air
quality and health, radiative transfer and climate. However, the importance
of this chemistry is uncertain as a consequence of limited understanding of
the abundance and atmospheric fate of SCIs. In this work we apply
experimental, theoretical and numerical modelling methods to quantify the
atmospheric impacts, abundance and fate of the structurally diverse SCIs
derived from the ozonolysis of monoterpenes, the second most abundant group
of unsaturated hydrocarbons in the atmosphere. We have investigated the
removal of SO<sub>2</sub> by SCIs formed from the ozonolysis of three
atmospherically important monoterpenes (<i>α</i>-pinene, <i>β</i>-pinene and
limonene) in the presence of varying amounts of water vapour in large-scale
simulation chamber experiments that are representative of boundary layer conditions.
The SO<sub>2</sub> removal displays a clear dependence on water vapour
concentration, but this dependence is not linear across the range of
[H<sub>2</sub>O] explored. At low [H<sub>2</sub>O] a strong dependence of SO<sub>2</sub>
removal on [H<sub>2</sub>O] is observed, while at higher [H<sub>2</sub>O] this dependence
becomes much weaker. This is interpreted as being caused by the production of
a variety of structurally (and hence chemically) different SCIs in each of the
systems studied, which displayed different rates of reaction with water and
of unimolecular rearrangement or decomposition. The determined rate constants,
<i>k</i>(SCI+H<sub>2</sub>O), for those SCIs that react primarily with H<sub>2</sub>O range
from 4 to 310  ×  10<sup>−15</sup> cm<sup>3</sup> s<sup>−1</sup>. For those SCIs that
predominantly react unimolecularly, determined rates range from
130 to 240 s<sup>−1</sup>. These values are in line with previous results for the
(analogous) stereo-specific SCI system of <i>syn</i>-/<i>anti</i>-CH<sub>3</sub>CHOO. The experimental results are
interpreted through theoretical studies of the SCI unimolecular reactions and
bimolecular reactions with H<sub>2</sub>O, characterised for <i>α</i>-pinene and
<i>β</i>-pinene at the M06-2X/aug-cc-pVTZ level of theory. The theoretically
derived rates agree with the experimental results within the uncertainties. A
global modelling study, applying the experimental results within the
GEOS-Chem chemical transport model, suggests that > 97 % of
the total monoterpene-derived global SCI burden is comprised of SCIs with a
structure that determines that they react slowly with water and that their atmospheric
fate is dominated by unimolecular reactions. Seasonally averaged boundary
layer concentrations of monoterpene-derived SCIs reach up to
1.4  ×  10<sup>4</sup> cm<sup>−3</sup> in regions of elevated monoterpene
emissions in the tropics. Reactions of monoterpene-derived SCIs with SO<sub>2</sub>
account for < 1 % globally but may account for up to 60 % of
the gas-phase SO<sub>2</sub> removal over areas of tropical forests, with
significant localised impacts on the formation of sulfate aerosol and hence
the lifetime and distribution of SO<sub>2</sub>
Two isomers of a bis(diphenylphosphino)phosphinine, and the synthesis and reactivity of Ru arene / Cp* phosphinophosphinine complexes
Reversible temperature-induced polymorphic phase transitions of [Y(OAr)<sub>3</sub>] and [Ce(OAr)<sub>3</sub>] (Ar=2,6-<sup>T</sup>Bu<sub>2</sub>-4-MeC<sub>6</sub>H<sub>2</sub>): Interconversions between pyramidal and planar geometries
Atmospheric isoprene ozonolysis: impacts of stabilised Criegee intermediate reactions with SO<sub>2</sub>, H<sub>2</sub>O and dimethyl sulfide
Isoprene is the dominant global biogenic volatile organic compound (VOC) emission. Reactions of isoprene with ozone are known to form stabilised Criegee intermediates (SCIs), which have recently been shown to be potentially important oxidants for SO2 and NO2 in the atmosphere; however the significance of this chemistry for SO2 processing (affecting sulfate aerosol) and NO2 processing (affecting NOx levels) depends critically upon the fate of the SCIs with respect to reaction with water and decomposition. Here, we have investigated the removal of SO2 in the presence of isoprene and ozone, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity, confirming a significant reaction for isoprene-derived SCIs with H2O. Under excess SO2 conditions, the total isoprene ozonolysis SCI yield was calculated to be 0.56 (+/-0.03). The observed SO2 removal kinetics are consistent with a relative rate constant, k (SCI + H2O) = k (SCI + SO2), of 3.1 (+/-0.5) x 10(-5) for isoprene-derived SCIs. The relative rate constant for k (SCI decomposition) = k (SCI + SO2) is 3.0 (+/-3.2) x 10(11) cm(-3). Uncertainties are +/-2 sigma and represent combined systematic and precision components. These kinetic parameters are based on the simplification that a single SCI species is formed in isoprene ozonolysis, an approximation which describes the results well across the full range of experimental conditions. Our data indicate that isoprenederived SCIs are unlikely to make a substantial contribution to gas-phase SO2 oxidation in the troposphere. We also present results from an analogous set of experiments, which show a clear dependence of SO2 removal in the isopreneozone system as a function of dimethyl sulfide concentration. We propose that this behaviour arises from a rapid reaction between isoprene-derived SCIs and dimethyl sulfide (DMS); the observed SO2 removal kinetics are consistent with a relative rate constant, k (SCI + DMS) = k (SCI + SO2), of 3.5 (+/-1.8). This result suggests that SCIs may contribute to the oxidation of DMS in the atmosphere and that this process could therefore influence new particle formation in regions impacted by emissions of unsaturated hydrocarbons and DMS
Level Crossing Analysis of Growing surfaces
We investigate the average frequency of positive slope ,
crossing the height in the surface growing processes. The
exact level crossing analysis of the random deposition model and the
Kardar-Parisi-Zhang equation in the strong coupling limit before creation of
singularities are given.Comment: 5 pages, two column, latex, three figure
Antibiotic prophylaxis is associated with subsequent resistant infections in children with an initial extended-spectrum-cephalosporin-resistant Enterobacteriaceae infection
ABSTRACT
The objective of this study was to assess the association between previous antibiotic use, particularly long-term prophylaxis, and the occurrence of subsequent resistant infections in children with index infections due to extended-spectrum-cephalosporin-resistant
Enterobacteriaceae
. We also investigated the concordance of the index and subsequent isolates. Extended-spectrum-cephalosporin-resistant
Escherichia coli
and
Klebsiella
spp. isolated from normally sterile sites of patients aged <22 years were collected along with associated clinical data from four freestanding pediatric centers. Subsequent isolates were categorized as concordant if the species, resistance determinants, and
fumC-fimH
(
E. coli
) or
tonB
(
Klebsiella pneumoniae
) type were identical to those of the index isolate. In total, 323 patients had 396 resistant isolates; 45 (14%) patients had ≥1 subsequent resistant infection, totaling 73 subsequent resistant isolates. The median time between the index and first subsequent infections was 123 (interquartile range, 43 to 225) days. In multivariable Cox proportional hazards analyses, patients were 2.07 times as likely to have a subsequent resistant infection (95% confidence interval, 1.11 to 3.87) if they received prophylaxis in the 30 days prior to the index infection. In 26 (58%) patients, all subsequent isolates were concordant with their index isolate, and 7 (16%) additional patients had at least 1 concordant subsequent isolate. In 12 of 17 (71%) patients with
E. coli
sequence type 131 (ST131)-associated type 40-30, all subsequent isolates were concordant. Subsequent extended-spectrum-cephalosporin-resistant infections are relatively frequent and are most commonly due to bacterial strains concordant with the index isolate. Further study is needed to assess the role prophylaxis plays in these resistant infections.
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