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  • 1
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    Online Resource
    Validation of the OAKS prognostic model for acute kidney injury after gastrointestinal surgery
    Oxford University Press (OUP) ; 2022
    In:  BJS Open Vol. 6, No. 1 ( 2022-01-06)
    Details
    In: BJS Open, Oxford University Press (OUP), Vol. 6, No. 1 ( 2022-01-06)
    Abstract: Postoperative acute kidney injury (AKI) is a common complication of major gastrointestinal surgery with an impact on short- and long-term survival. No validated system for risk stratification exists for this patient group. This study aimed to validate externally a prognostic model for AKI after major gastrointestinal surgery in two multicentre cohort studies. Methods The Outcomes After Kidney injury in Surgery (OAKS) prognostic model was developed to predict risk of AKI in the 7 days after surgery using six routine datapoints (age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker). Validation was performed within two independent cohorts: a prospective multicentre, international study (‘IMAGINE’) of patients undergoing elective colorectal surgery (2018); and a retrospective regional cohort study (‘Tayside’) in major abdominal surgery (2011–2015). Multivariable logistic regression was used to predict risk of AKI, with multiple imputation used to account for data missing at random. Prognostic accuracy was assessed for patients at high risk (greater than 20 per cent) of postoperative AKI. Results In the validation cohorts, 12.9 per cent of patients (661 of 5106) in IMAGINE and 14.7 per cent (106 of 719 patients) in Tayside developed 7-day postoperative AKI. Using the OAKS model, 558 patients (9.6 per cent) were classified as high risk. Less than 10 per cent of patients classified as low-risk developed AKI in either cohort (negative predictive value greater than 0.9). Upon external validation, the OAKS model retained an area under the receiver operating characteristic (AUC) curve of range 0.655–0.681 (Tayside 95 per cent c.i. 0.596 to 0.714; IMAGINE 95 per cent c.i. 0.659 to 0.703), sensitivity values range 0.323–0.352 (IMAGINE 95 per cent c.i. 0.281 to 0.368; Tayside 95 per cent c.i. 0.253 to 0.461), and specificity range 0.881–0.890 (Tayside 95 per cent c.i. 0.853 to 0.905; IMAGINE 95 per cent c.i. 0.881 to 0.899). Conclusion The OAKS prognostic model can identify patients who are not at high risk of postoperative AKI after gastrointestinal surgery with high specificity. Presented to Association of Surgeons in Training (ASiT) International Conference 2018 (Edinburgh, UK), European Society of Coloproctology (ESCP) International Conference 2018 (Nice, France), SARS (Society of Academic and Research Surgery) 2020 (Virtual, UK).
    Type of Medium: Online Resource
    ISSN: 2474-9842
    URL: Article
    DOI: 10.1093/bjsopen/zrab150
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
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  • 2
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    Estimating collision–coalescence rates from in situ observations of marine stratocumulus
    Wiley ; 2017
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 143, No. 708 ( 2017-10), p. 2755-2763
    Details
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 143, No. 708 ( 2017-10), p. 2755-2763
    Abstract: Precipitation forms in warm clouds via collision–coalescence. This process is difficult to observe directly in situ and its implementation in numerical models is uncertain. We use aircraft observations of the drop‐size distribution (DSD) near marine stratocumulus tops to estimate collision–coalescence rates. Marine stratocumulus is a useful system to study collisional growth because it is initiated near the cloud top and the clouds evolve slowly enough to obtain statistically useful data from aircraft. We compare rate constants estimated from observations with reference rate constants derived from a collision–coalescence box model, the result of which is termed the enhancement factor (EF). We evaluate two hydrodynamic collision–coalescence kernels, one quiescent and one including the effects of small‐scale turbulence. Due to sampling volume limitations, DSDs must be averaged over length‐scales much greater than those relevant to the underlying physics, such that we also examine the role of averaging length‐scale with respect to process representation. Averaging length‐scales of 1.5 and 30 km are used, corresponding roughly to the horizontal grid lengths of cloud‐resolving models and high‐resolution climate models, respectively. EF values range from 0.1 to 40, with the greatest EFs associated with small mode diameter cases and a generally decreasing trend with drop size. For any given drop size or averaging length‐scale, there is about an order of magnitude variability in EFs. These results suggest that spatial variability on length‐scales smaller than 1.5 km prevents accurate retrieval of rate constants from large‐scale average DSDs. Large‐scale models must therefore account for small‐scale variability to represent cloud microphysical processes accurately. The turbulent kernel reduces EFs for all drop sizes, but can only account for at most half of the calculated EFs in marine stratocumulus.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    URL: Article
    DOI: 10.1002/qj.2017.143.issue-708
    DOI: 10.1002/qj.3124
    RVK:
    UA 1000
    RVK:
    UA 7650
    Language: English
    Publisher: Wiley
    Publication Date: 2017
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  • 3
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    Kinetic limitations on cloud droplet formation and impact on cloud albedo
    Stockholm University Press ; 2001
    In:  Tellus B Vol. 53, No. 2 ( 2001-04), p. 133-149
    Details
    In: Tellus B, Stockholm University Press, Vol. 53, No. 2 ( 2001-04), p. 133-149
    Type of Medium: Online Resource
    ISSN: 0280-6509 , 1600-0889
    URL: Article
    DOI: 10.1034/j.1600-0889.2001.d01-12.x
    RVK:
    RA 1000
    RVK:
    UA 8382.2
    Language: English
    Publisher: Stockholm University Press
    Publication Date: 2001
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    SSG: 16,13
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  • 4
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    Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation
    American Geophysical Union (AGU) ; 2018
    In:  Journal of Geophysical Research: Atmospheres Vol. 123, No. 7 ( 2018-04-16), p. 3704-3723
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 123, No. 7 ( 2018-04-16), p. 3704-3723
    Abstract: Three characteristic in‐cloud vertical concentration profiles are identified: those that peak at the base, middle, and top of cloud Nonreactive surface‐derived species present the in‐cloud vertical concentration profiles that are most influenced by rainout Rainout loss frequency is greatest at cloud base for moderate‐drizzling thick clouds, and at cloud top for light‐drizzling thin clouds
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrd.v123.7
    DOI: 10.1002/2017JD027900
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2018
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  • 5
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    Comparison of Observed and Simulated Drop Size Distributions from Large-Eddy Simulations with Bin Microphysics
    American Meteorological Society ; 2019
    In:  Monthly Weather Review Vol. 147, No. 2 ( 2019-02-01), p. 477-493
    Details
    In: Monthly Weather Review, American Meteorological Society, Vol. 147, No. 2 ( 2019-02-01), p. 477-493
    Abstract: Two case studies of marine stratocumulus (one nocturnal and drizzling, the other daytime and nonprecipitating) are simulated by the UCLA large-eddy simulation model with bin microphysics for comparison with aircraft in situ observations. A high-bin-resolution variant of the microphysics is implemented for closer comparison with cloud drop size distribution (DSD) observations and a turbulent collision–coalescence kernel to evaluate the role of turbulence on drizzle formation. Simulations agree well with observational constraints, reproducing observed thermodynamic profiles (i.e., liquid water potential temperature and total moisture mixing ratio) as well as liquid water path. Cloud drop number concentration and liquid water content profiles also agree well insofar as the thermodynamic profiles match observations, but there are significant differences in DSD shape among simulations that cause discrepancies in higher-order moments such as sedimentation flux, especially as a function of bin resolution. Counterintuitively, high-bin-resolution simulations produce broader DSDs than standard resolution for both cases. Examination of several metrics of DSD width and percentile drop sizes shows that various discrepancies of model output with respect to the observations can be attributed to specific microphysical processes: condensation spuriously creates DSDs that are too wide as measured by standard deviation, which leads to collisional production of too many large drops. The turbulent kernel has the greatest impact on the low-bin-resolution simulation of the drizzling case, which exhibits greater surface precipitation accumulation and broader DSDs than the control (quiescent kernel) simulations. Turbulence effects on precipitation formation cannot be definitively evaluated using bin microphysics until the artificial condensation broadening issue has been addressed.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    URL: Article
    DOI: 10.1175/MWR-D-18-0242.1
    RVK:
    RA 1000
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2019
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    SSG: 14
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  • 6
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    New Observations of Precipitation Initiation in Warm Cumulus Clouds
    American Meteorological Society ; 2008
    In:  Journal of the Atmospheric Sciences Vol. 65, No. 9 ( 2008-09-01), p. 2972-2982
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 65, No. 9 ( 2008-09-01), p. 2972-2982
    Abstract: The mechanism responsible for formation of rain in warm clouds has been debated for over six decades. Here, the authors analyze new measurements of shallow cumulus made with a phase Doppler interferometer during the Rain in Cumulus over the Ocean (RICO) experiment. These observations show that drops sufficiently large ( & gt;55-μm diameter) to initiate precipitation (termed collision–coalescence initiators or CCIs) are found preferentially at cloud top, tend to cluster with each other, and are found in environments that are thermodynamically, dynamically, and microphysically distinct from those of smaller drops. The CCI environments exhibit cloud spectra that are shifted to larger sizes, with enhanced broadening toward larger drop sizes. Increased entrainment is also associated with CCIs, suggesting that it is an important process in CCI production. A simple model combining inhomogeneous mixing and condensation is inadequate to explain these observations. It is hypothesized that CCIs are produced in cloud-top regions where turbulence generated by entrainment mixing locally enhances collision–coalescence rates.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/2008JAS2600.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2008
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    SSG: 16,13
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  • 7
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    Stratocumulus Cloud Clearings and Notable Thermodynamic and Aerosol Contrasts across the Clear–Cloudy Interface
    American Meteorological Society ; 2016
    In:  Journal of the Atmospheric Sciences Vol. 73, No. 3 ( 2016-03-01), p. 1083-1099
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 73, No. 3 ( 2016-03-01), p. 1083-1099
    Abstract: Data from three research flights, conducted over water near the California coast, are used to investigate the boundary between stratocumulus cloud decks and clearings of different sizes. Large clearings exhibit a diurnal cycle with growth during the day and contraction overnight and a multiday life cycle that can include oscillations between growth and decay, whereas a small coastal clearing was observed to be locally confined with a subdiurnal lifetime. Subcloud aerosol characteristics are similar on both sides of the clear–cloudy boundary in the three cases, while meteorological properties exhibit subtle, yet important, gradients, implying that dynamics, and not microphysics, is the primary driver for the clearing characteristics. Transects, made at multiple levels across the cloud boundary during one flight, highlight the importance of microscale (~1 km) structure in thermodynamic properties near the cloud edge, suggesting that dynamic forcing at length scales comparable to the convective eddy scale may be influential to the larger-scale characteristics of the clearing. These results have implications for modeling and observational studies of marine boundary layer clouds, especially in relation to aerosol–cloud interactions and scales of variability responsible for the evolution of stratocumulus clearings.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-15-0137.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
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    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 8
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    Statistical comparison of properties of simulated and observed cumulus clouds in the vicinity of Houston during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)
    American Geophysical Union (AGU) ; 2008
    In:  Journal of Geophysical Research Vol. 113, No. D13 ( 2008-07-03)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 113, No. D13 ( 2008-07-03)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2007JD009304
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2008
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    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 9
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    Inertial Clustering of Particles in High-Reynolds-Number Turbulence
    American Physical Society (APS) ; 2008
    In:  Physical Review Letters Vol. 100, No. 21 ( 2008-5-28)
    Details
    In: Physical Review Letters, American Physical Society (APS), Vol. 100, No. 21 ( 2008-5-28)
    Type of Medium: Online Resource
    ISSN: 0031-9007 , 1079-7114
    URL: Article
    DOI: 10.1103/PhysRevLett.100.214501
    RVK:
    UA 1000
    RVK:
    UA 6520
    Language: English
    Publisher: American Physical Society (APS)
    Publication Date: 2008
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    detail.hit.zdb_id: 208853-8
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  • 10
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    Aerosol Impacts on Climate and Biogeochemistry
    Annual Reviews ; 2011
    In:  Annual Review of Environment and Resources Vol. 36, No. 1 ( 2011-11-21), p. 45-74
    Details
    In: Annual Review of Environment and Resources, Annual Reviews, Vol. 36, No. 1 ( 2011-11-21), p. 45-74
    Abstract: Aerosols are suspensions of solid and/or liquid particles in the atmosphere and modify atmospheric radiative fluxes and chemistry. Aerosols move mass from one part of the earth system to other parts of the earth system, thereby modifying biogeochemistry and the snow surface albedo. This paper reviews our understanding of the impacts of aerosols on climate through direct radiative changes, aerosol-cloud interactions (indirect effects), atmospheric chemistry, snow albedo, and land and ocean biogeochemistry. Aerosols play an important role in the preindustrial (natural) climate system and have been perturbed substantially over the anthropocene, often directly by human activity. The most important impacts of aerosols, in terms of climate forcing, are from the direct and indirect effects, with large uncertainties. Similarly large impacts of aerosols on land and ocean biogeochemistry have been estimated, but these have larger uncertainties.
    Type of Medium: Online Resource
    ISSN: 1543-5938 , 1545-2050
    URL: Issue
    URL: Article
    DOI: 10.1146/energy.2011.36.issue-1
    DOI: 10.1146/annurev-environ-042009-094507
    Language: English
    Publisher: Annual Reviews
    Publication Date: 2011
    detail.hit.zdb_id: 2182174-4
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