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Optical parametric chirped-pulse amplification (OPCPA) [Dubietis et al., Opt. Commun. 88, 437 (1992)] implemented by multikilojoule Nd:glass pump lasers is a promising approach to produce ultraintense pulses (
). Technologies are being developed to upgrade the OMEGA EP Laser System with the goal to pump an optical parametric amplifier line (EP OPAL) with two of the OMEGA EP beamlines. The resulting ultraintense pulses (1.5 kJ, 20 fs,
) would be used jointly with picosecond and nanosecond pulses produced by the other two beamlines. A midscale OPAL pumped by the Multi-Terawatt (MTW) laser is being constructed to produce 7.5-J, 15-fs pulses and demonstrate scalable technologies suitable for the upgrade. MTW OPAL will share a target area with the MTW laser (50 J, 1 to 100 ps), enabling several joint-shot configurations. We report on the status of the MTW OPAL system, and the technology development required for this class of all-OPCPA laser system for ultraintense pulses.
To identify modifiable risk factors for acquisition of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae (KPC) colonization among long-term acute-care hospital (LTACH) patients.
Multicenter, matched case-control study.
Four LTACHs in Chicago, Illinois.
Each case patient included in this study had a KPC-negative rectal surveillance culture on admission followed by a KPC-positive surveillance culture later in the hospital stay. Each matched control patient had a KPC-negative rectal surveillance culture on admission and no KPC isolated during the hospital stay.
From June 2012 to June 2013, 2,575 patients were admitted to 4 LTACHs; 217 of 2,144 KPC-negative patients (10.1%) acquired KPC. In total, 100 of these patients were selected at random and matched to 100 controls by LTACH facility, admission date, and censored length of stay. Acquisitions occurred a median of 16.5 days after admission. On multivariate analysis, we found that exposure to higher colonization pressure (OR, 1.02; 95% CI, 1.01–1.04; P=.002), exposure to a carbapenem (OR, 2.25; 95% CI, 1.06–4.77; P=.04), and higher Charlson comorbidity index (OR, 1.14; 95% CI, 1.01–1.29; P=.04) were independent risk factors for KPC acquisition; the odds of KPC acquisition increased by 2% for each 1% increase in colonization pressure.
Higher colonization pressure, exposure to carbapenems, and a higher Charlson comorbidity index independently increased the odds of KPC acquisition among LTACH patients. Reducing colonization pressure (through separation of KPC-positive patients from KPC-negative patients using strict cohorts or private rooms) and reducing carbapenem exposure may prevent KPC cross transmission in this high-risk patient population.
Prevalence of blaKPC-encoding Enterobacteriaceae (KPC) in Chicago long-term acute care hospitals (LTACHs) rose rapidly after the first recognition in 2007. We studied the epidemiology and transmission capacity of KPC in LTACHs and the effect of patient cohorting.
Data were available from 4 Chicago LTACHs from June 2012 to June 2013 during a period of bundled interventions. These consisted of screening for KPC rectal carriage, daily chlorhexidine bathing, medical staff education, and 3 cohort strategies: a pure cohort (all KPC-positive patients on 1 floor), single rooms for KPC-positive patients, and a mixed cohort (all KPC-positive patients on 1 floor, supplemented with KPC-negative patients). A data-augmented Markov chain Monte Carlo (MCMC) method was used to model the transmission process.
Average prevalence of KPC colonization was 29.3%. On admission, 18% of patients were colonized; the sensitivity of the screening process was 81%. The per admission reproduction number was 0.40. The number of acquisitions per 1,000 patient days was lowest in LTACHs with a pure cohort ward or single rooms for colonized patients compared with mixed-cohort wards, but 95% credible intervals overlapped.
Prevalence of KPC in LTACHs is high, primarily due to high admission prevalence and the resultant impact of high colonization pressure on cross transmission. In this setting, with an intervention in place, patient-to-patient transmission is insufficient to maintain endemicity. Inclusion of a pure cohort or single rooms for KPC-positive patients in an intervention bundle seemed to limit transmission compared to use of a mixed cohort.
Infect Control Hosp Epidemiol 2015;36(10):1148–1154
To identify differences in organizational culture and better understand motivators to implementation of abundle intervention to control Klebsiella pneumoniae carbapenemase–producing Enterobacteriaceae (KPC).
Four long-term acute care hospitals (LTACHs) in Chicago.
LTACH staff across 3 strata of employees (administration, midlevel management, and frontline clinical workers).
Qualitative interviews or focus groups and completion of a quantitative questionnaire.
Eighty employees (frontline, 72.5%; midlevel, 17.5%; administration, 10%) completed surveys and participated in qualitative discussions in August 2012. Although 82.3% of respondents felt that quality improvement was a priority at their LTACH, there were statistically significant differences in organizational culture between staff strata, with administrative-level having higher organizational culture scores (ie, more favorable responses) than midlevel or frontline staff. When asked to rank the success of the KPC control program, mean response was 8.0 (95% confidence interval, 7.6–8.5), indicating a high level of agreement with the perception that the program was a success. Patient safety and personal safety were reported most often as personal motivators for intervention adherence. The most convergent theme related to prevention across groups was that proper hand hygiene is vital to prevention of KPC transmission.
Despite differences in organizational culture across 3 strata of LTACH employees, the high degree of convergence in motivation, understanding, and beliefs related to implementation of a KPC control bundle suggests that all levels of staff may be able to align perspectives when faced with a key infection control problem and quality improvement initiative.
We evaluated the effectiveness of daily chlorhexidine gluconate (CHG) bathing in decreasing skin carriage of Klebsiella pneumoniae carbapenemase–producing Enterobacteriaceae (KPC) among long-term acute care hospital patients. CHG bathing reduced KPC skin colonization, particularly when CHG skin concentrations greater than or equal to 128 μg/mL were achieved.
Diversity within Shigella dysenteriae (n=40) and Shigella boydii (n=30) isolates from children living in Egypt aged <5 years was investigated. Shigella-associated diarrhoea occurred mainly in summer months and in children aged <3 years, it commonly presented with vomiting and fever. Serotypes 7 (30%), 2 (28%), and 3 (23%) accounted for most of S. dysenteriae isolates; 50% of S. boydii isolates were serotype 2. S. dysenteriae and S. boydii isolates were often resistant to ampicillin, chloramphenicol and tetracycline (42%, 17%, respectively), although resistance varied among serotypes. Pulsed-field gel electrophoresis separated the isolates into distinct clusters correlating with species and serotype. Genetic differences in trimethoprim/sulfamethoxazole and β-lactam-encoding resistance genes were also evident. S. dysenteriae and S. boydii are genetically diverse pathogens in Egypt; the high level of multidrug resistance associated with both pathogens and resistance to the most available inexpensive antibiotics underlines the importance of continuing surveillance.
An MOCVD grown InP based optothyristor has been fabricated and tested for high power pulsed switching applications. To increase the power handling capability, the thyristor structure has a 250 μm thick Fe doped semi-insulating (SI) InP sandwiched between two pn junctions of a conventional thyristor. The turn-on of the thyristor is controlled by optical illumination on the SI-InP which creates a high concentration of electron and hole pairs. More than 1,100 V device hold-off voltage has been observed and over 66 A switched current has been realized with a di/dt rating of 1.38×1010 A/s. The switched current as a function of switch voltage and of optical illumination power has also been studied. Comparison with the switching characteristics of a bulk SI-InP photoconductive switch clearly indicates the advantage of this optothyristor in terms of power handling capability.
Recent progress of GaAs-on-Si technology is reviewed and the importance of initial nucleation is emphasized. Growth initiation with a Ga prelayer at a suitable low temperature combined with migration enhanced epitaxy and in-situ thermal annealing has a prospect of giving substantially improved material quality. During the initial growth, use of the minimum necessary As4/Ga flux ratio is found to be critical. The random alignment of the major axis of the oval defects is suggested to be an alternative simple technique to detect the presence of antiphase domains. Patterned growth or post growth patterning releases tensile stress only if the growth edges are free. GaAs-on-Si was completely relaxed from stress by post-growth patterning to 5 μm × 5 μm size patterns. Steps on the surface due to substrate misorientation do not affect the two dimensional electron gas (2DEG) transport properties in AlGaAs/GaAs selectively doped heterojunction transistor (SDHT) structures. For a sheet density of 1012 cm−2, the 2DEG mobility >50,000 cm2V−1s−1 at 77 K was obtained on Si substrates, which is sufficient for fabrication of high performance SDHTs. The study shows that GaAs-on-Si has a great potential for SDHT technology.
A high performance, Al0.3Ga0.7As/GaAs based, optically gated thyristor with a bulk semi-insulating(SI) GaAs 650 μm in thickness as the voltage blocking layer has been fabricated and characterized for high power pulsed switching applications. Low temperature(LT) GaAs was used to passivate the device surface and was found to greatly improve the switch hold-off voltage. The switched current as a function of bias up to 2,200 V (34 kV/cm) has been tested and the maximum switched current was 240 A with a di/dt equal to 2.02×1010 A/s. The forward dynamic current-voltage characteristics have been measured and the dissipated energy per switching determined. It was found that very sensitive triggering of the switch is possible, even with a light emitting diode operating in the sub-mW range, when the thyristor is reverse biased. The sensitive triggering is a result of the carrier tunneling through the reverse biased pn junctions.
Static quantum ab initio and quantum semiempirical molecular dynamics calculations were employed to study reconstructions of (100) diamond surfaces in presence of hydrogen and oxygen. The results indicate that the energetically most favorable structures of oxygenated surfaces are those with chemisorbed hydroxyl groups. It was found that hydrogen bonds are formed among chemisorbed oxygenated species. The formation of these hydrogen bonds is shown to be an important factor in stabilization of adlayers. A number of important vibrational modes characteristic of oxygenated diamond surfaces were identified. The analysis of surface vibrational spectra demonstrates the influence of the local environment on the position of vibrational modes and can be useful for interpretation of experimental data.
The mechanism of action of electroconvulsive therapy (ECT) in treating major depression is unknown. We studied two candidate mechanisms through inhibiting simultaneously the synthesis of noradrenaline and serotonin in patients immediately after successful treatment with ECT using a randomised, placebo-controlled, double-blind crossover design. There were no significant changes in depression scores under any experimental conditions, or between the amine-depleted and placebo groups despite reductions of 61% in serum homovanillic acid, 47% in 3-methoxy-4-hydroxyenylethyleneglycol, and 89% in serum tryptophan. Catecholamine and serotonin availability may not be necessary for maintaining the initial antidepressant response to ECT.
The characteristics of fluoroquinolone use that increase the risk of selecting for fluoroquinolone resistance remain unclear. Exposure to subtherapeutic levels of fluoroquinolone promotes bacterial development of fluoroquinolone resistance. Oral fluoroquinolone absorption is significantly impaired by coadministration with many common di- or tri-valent cation-containing compounds (DTCCs), and this interaction has been associated with therapeutic failure. However, the prevalence of, and risk factors for, in-hospital coadministration of oral fluoroquinolones with DTCCs is unknown.
A 625-bed, tertiary-care medical center.
All inpatients who were dispensed oral levofloxacin from July 1, 1999, to June 30, 2001, were included. Coadministration was defined by documented administration of any DTCC within 2 hours of levofloxacin. Complete coadministration was defined as coadministration complicating every dose of a course of levofloxacin.
A subset of 3,227 (41.0%) of 7,871 doses of levofloxacin that occurred during the same calendar day as any DTCC was selected for further review. Overall, 1,904 (77.1%) of 2,470 doses of oral levofloxacin reviewed were complicated by coadministration with at least one DTCC. On multivariable analysis, an increased number of prescribed medications was significantly associated with complete coadministration (per increase of one medication: OR, 1.05; CI95, 1.01–1.10; P = .036), whereas patient location in an ICU was protective (OR, 0.51; CI95, 0.30–0.87; P = .013). If our prevalence results are extrapolated to all patients receiving oral levofloxacin at our hospital, approximately one in three doses was complicated by coadministration.
Coadministration of fluoroquinolones with DTCCs is extremely common and significantly associated with polypharmacy.