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1.
J Environ Qual ; 49(5): 1110-1125, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016464

RESUMO

Certain aspects in the collection, handling, storage, and subsequent analysis of discrete air samples from non-steady-state flux chambers are critical to generating accurate and unbiased estimates of nitrous oxide (N2 O) fluxes. The focus of this paper is on air sample collection and storage in small vials (<12 ml) primarily for gas chromatography (GC) analysis. Sample integrity is assured through following simple procedures including storage under pressure and analysis within a few months of collection. Concurrent storage of standards in an identical manner to samples is recommended and allows the storage period to be reliably extended. In the laboratory, an autosampler is typically used in batch analysis of ∼200 sequentially analyzed samples by GC with an electron capture detector (ECD). Some comparisons are given between GC and alternatives including optical N2 O detectors that are increasingly being used for high-precision N2 O measurement. The importance of calibration and traceability of gas standards is discussed, where high-quality standards ensure the most accurate assessment of N2 O concentration and comparability between laboratories. The calibration allows a consistent and best estimate of flux to be derived.


Assuntos
Óxido Nitroso , Calibragem , Cromatografia Gasosa
2.
Water Sci Technol ; 82(5): 927-939, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33031071

RESUMO

UV/Vis spectrometers are powerful tools for online monitoring of wastewater constituents and processes. However, most studies only focus on typical parameters such as chemical oxygen demand (COD) and total suspended solids. This work presents a multi-parameter approach for calibration of a UV/Vis spectrometer for online monitoring of sewer systems. Parameters studied include soluble and total COD, nitrate, ammonium, sulphate and orthophosphate, as well as total dissolved sulphide, bisulphide and hydrogen sulphide, because they are one of the main causes for odour and corrosion in sewer systems. Two calibration methods are compared: multiple linear regression included in the manufacturer's software, and partial least square (PLS) computed using the pls package of the R library. Performance of the methods is evaluated for calibration and validation data sets employing four different criteria: relative root mean square error (RMSErel), RMSE-observations standard deviation ratio, Nash-Sutcliffe efficiency and percentage bias. A method-parameter dependency was revealed during the calibration phase but, when predicting new data, the PLS method showed higher robustness for almost all parameters. Both methods were able to predict concentration trends associated with sewer processes, some of which are strongly correlated to the sulphide species.


Assuntos
Águas Residuárias , Análise da Demanda Biológica de Oxigênio , Calibragem , Análise dos Mínimos Quadrados , Espectrofotometria Ultravioleta
3.
Nan Fang Yi Ke Da Xue Xue Bao ; 40(6): 799-805, 2020 Jun 30.
Artigo em Chinês | MEDLINE | ID: mdl-32895192

RESUMO

ObjectiveTo explore a method for calculating water equivalent diameter (Dw) based on localizer CT images for calculation of the size specific dose estimates (SSDE).MethodGE Revolution CT and LightSpeed VCT were used to scan CT dose index phantoms 16 cm and 32 cm in diameter at the tube voltages of 80, 100 and 120 kV to obtain the axial image and anteroposterior localizer radiograph. According to the definition of CT Hounsfield unit, the axial images were used to calculate the conversion factors that convert the phantom thickness to water equivalent thickness. The gray value of the localizer radiograph and the water equivalent thickness were calibrated with a linear equation, and the parameters of the calibration were used to calculate the water equivalent thickness. The method was verified using 2 CT dose index phantoms and in 22 patients undergoing chest and abdominal CT examination.ResultComparison of the water equivalent diameter (Dw) based on the localizer radiograph and axial image of the 2 phantoms showed that the percentage difference between Dw from the axial images and from the localizer radiograph was below 3%. The trend of Dw variations with location in the two methods was sonsistent. The difference in Dw in intermediate region of interest between the axial image and the localizer radiograph from the 22 patients was below 6.6%. With the mean Dw in the ROI, the maximum percentage difference was 7.5%.ConclusionCalibration of the gray value of the localizer radiograph and the water equivalent thickness using the axial image and localizer radiograph of CT dose index phantoms allows quick calculation of the SSDE based on the parameters of calibration.


Assuntos
Tomografia Computadorizada por Raios X , Calibragem , Humanos , Imagens de Fantasmas , Doses de Radiação , Água
4.
Am J Bot ; 107(8): 1165-1176, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32864740

RESUMO

PREMISE: Within closed-canopy forests, vertical gradients of light and atmospheric CO2 drive variations in leaf carbon isotope ratios, leaf mass per area (LMA), and the micromorphology of leaf epidermal cells. Variations in traits observed in preserved or fossilized leaves could enable inferences of past forest canopy closure and leaf function and thereby habitat of individual taxa. However, as yet no calibration study has examined how isotopic, micro- and macromorphological traits, in combination, reflect position within a modern closed-canopy forest or how these could be applied to the fossil record. METHODS: Leaves were sampled from throughout the vertical profile of the tropical forest canopy using the 48.5 m crane at the Daintree Rainforest Observatory, Queensland, Australia. Carbon isotope ratios, LMA, petiole metric (i.e., petiole-width2 /leaf area, a proposed proxy for LMA that can be measured from fossil leaves), and leaf micromorphology (i.e., undulation index and cell area) were compared within species across a range of canopy positions, as quantified by leaf area index (LAI). RESULTS: Individually, cell area, δ13 C, and petiole metric all correlated with both LAI and LMA, but the use of a combined model provided significantly greater predictive power. CONCLUSIONS: Using the observed relationships with leaf carbon isotope ratio and morphology to estimate the range of LAI in fossil floras can provide a measure of canopy closure in ancient forests. Similarly, estimates of LAI and LMA for individual taxa can provide comparative measures of light environment and growth strategy of fossil taxa from within a flora.


Assuntos
Floresta Úmida , Árvores , Austrália , Calibragem , Fósseis , Fotossíntese , Folhas de Planta , Queensland
5.
Value Health ; 23(9): 1163-1170, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32940234

RESUMO

OBJECTIVES: The cardiovascular outcomes challenge examined the predictive accuracy of 10 diabetes models in estimating hard outcomes in 2 recent cardiovascular outcomes trials (CVOTs) and whether recalibration can be used to improve replication. METHODS: Participating groups were asked to reproduce the results of the Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME) and the Canagliflozin Cardiovascular Assessment Study (CANVAS) Program. Calibration was performed and additional analyses assessed model ability to replicate absolute event rates, hazard ratios (HRs), and the generalizability of calibration across CVOTs within a drug class. RESULTS: Ten groups submitted results. Models underestimated treatment effects (ie, HRs) using uncalibrated models for both trials. Calibration to the placebo arm of EMPA-REG OUTCOME greatly improved the prediction of event rates in the placebo, but less so in the active comparator arm. Calibrating to both arms of EMPA-REG OUTCOME individually enabled replication of the observed outcomes. Using EMPA-REG OUTCOME-calibrated models to predict CANVAS Program outcomes was an improvement over uncalibrated models but failed to capture treatment effects adequately. Applying canagliflozin HRs directly provided the best fit. CONCLUSIONS: The Ninth Mount Hood Diabetes Challenge demonstrated that commonly used risk equations were generally unable to capture recent CVOT treatment effects but that calibration of the risk equations can improve predictive accuracy. Although calibration serves as a practical approach to improve predictive accuracy for CVOT outcomes, it does not extrapolate generally to other settings, time horizons, and comparators. New methods and/or new risk equations for capturing these CV benefits are needed.


Assuntos
Modelos Econômicos , Avaliação de Resultados em Cuidados de Saúde/métodos , Compostos Benzidrílicos/uso terapêutico , Calibragem , Canagliflozina/uso terapêutico , Doenças Cardiovasculares/complicações , Doenças Cardiovasculares/tratamento farmacológico , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/tratamento farmacológico , Glucosídeos/uso terapêutico , Humanos , Medição de Risco , Inibidores do Transportador 2 de Sódio-Glicose/uso terapêutico
6.
Chaos ; 30(7): 071101, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32752627

RESUMO

The ongoing novel coronavirus epidemic was announced a pandemic by the World Health Organization on March 11, 2020, and the Government of India declared a nationwide lockdown on March 25, 2020 to prevent community transmission of the coronavirus disease (COVID)-19. Due to the absence of specific antivirals or vaccine, mathematical modeling plays an important role in better understanding the disease dynamics and in designing strategies to control the rapidly spreading infectious disease. In our study, we developed a new compartmental model that explains the transmission dynamics of COVID-19. We calibrated our proposed model with daily COVID-19 data for four Indian states, namely, Jharkhand, Gujarat, Andhra Pradesh, and Chandigarh. We study the qualitative properties of the model, including feasible equilibria and their stability with respect to the basic reproduction number R0. The disease-free equilibrium becomes stable and the endemic equilibrium becomes unstable when the recovery rate of infected individuals increases, but if the disease transmission rate remains higher, then the endemic equilibrium always remains stable. For the estimated model parameters, R0>1 for all four states, which suggests the significant outbreak of COVID-19. Short-time prediction shows the increasing trend of daily and cumulative cases of COVID-19 for the four states of India.


Assuntos
Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/transmissão , Pneumonia Viral/epidemiologia , Pneumonia Viral/transmissão , Algoritmos , Número Básico de Reprodução , Betacoronavirus , Calibragem , Simulação por Computador , Surtos de Doenças , Previsões , Humanos , Índia/epidemiologia , Modelos Lineares , Pandemias
7.
Chaos ; 30(7): 071102, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32752644

RESUMO

We uncover and highlight the importance of social distancing duration and intensity in lowering hospitalization demand-to-supply during the coronavirus disease 2019 (COVID-19) epidemic in the USA. We have developed an epidemic progression model involving the susceptible-exposed-infected-recovered dynamics, the age-stratified disease transmissibility, and the possible large-scale undocumented (i.e., asymptomatic and/or untested) transmission of COVID-19 taking place in the USA. Our analysis utilizes COVID-19 observational data in the USA between March 19 and 28, corresponding to the early stage of the epidemic when the impacts of social distancing on disease progression were yet to manifest. Calibrating our model using epidemiological data from this time period enabled us to unbiasedly address the question "How long and with what intensity does the USA need to implement social distancing intervention during the COVID-19 pandemic?" For a short (i.e., up to two weeks) duration, we find a near-linear decrease in hospital beds demand with increasing intensity (φ) of social distancing. For a duration longer than two weeks, our findings highlight the diminishing marginal benefit of social distancing, characterized by a linear decrease in medical demands against an exponentially increasing social distancing duration. Long-term implementation of strict social distancing with φ>50% could lead to the emergence of a second wave of infections due to a large residual susceptible population which highlights the need for contact tracing and isolation before re-opening of the economy. Finally, we investigate the scenario of intermittent social distancing and find an optimal social-to-no-distancing duration ratio of 5:1 corresponding to a sustainable reduction in medical demands.


Assuntos
Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Hospitalização/estatística & dados numéricos , Pandemias/prevenção & controle , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Quarentena , Isolamento Social , Algoritmos , Betacoronavirus , Calibragem , Progressão da Doença , Epidemias , Humanos , Modelos Teóricos , Informática em Saúde Pública , Estados Unidos/epidemiologia
8.
BMJ ; 370: m2614, 2020 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-32732303

RESUMO

OBJECTIVE: To evaluate the performance of diagnostic prediction models for ovarian malignancy in all patients with an ovarian mass managed surgically or conservatively. DESIGN: Multicentre cohort study. SETTING: 36 oncology referral centres (tertiary centres with a specific gynaecological oncology unit) or other types of centre. PARTICIPANTS: Consecutive adult patients presenting with an adnexal mass between January 2012 and March 2015 and managed by surgery or follow-up. MAIN OUTCOME MEASURES: Overall and centre specific discrimination, calibration, and clinical utility of six prediction models for ovarian malignancy (risk of malignancy index (RMI), logistic regression model 2 (LR2), simple rules, simple rules risk model (SRRisk), assessment of different neoplasias in the adnexa (ADNEX) with or without CA125). ADNEX allows the risk of malignancy to be subdivided into risks of a borderline, stage I primary, stage II-IV primary, or secondary metastatic malignancy. The outcome was based on histology if patients underwent surgery, or on results of clinical and ultrasound follow-up at 12 (±2) months. Multiple imputation was used when outcome based on follow-up was uncertain. RESULTS: The primary analysis included 17 centres that met strict quality criteria for surgical and follow-up data (5717 of all 8519 patients). 812 patients (14%) had a mass that was already in follow-up at study recruitment, therefore 4905 patients were included in the statistical analysis. The outcome was benign in 3441 (70%) patients and malignant in 978 (20%). Uncertain outcomes (486, 10%) were most often explained by limited follow-up information. The overall area under the receiver operating characteristic curve was highest for ADNEX with CA125 (0.94, 95% confidence interval 0.92 to 0.96), ADNEX without CA125 (0.94, 0.91 to 0.95) and SRRisk (0.94, 0.91 to 0.95), and lowest for RMI (0.89, 0.85 to 0.92). Calibration varied among centres for all models, however the ADNEX models and SRRisk were the best calibrated. Calibration of the estimated risks for the tumour subtypes was good for ADNEX irrespective of whether or not CA125 was included as a predictor. Overall clinical utility (net benefit) was highest for the ADNEX models and SRRisk, and lowest for RMI. For patients who received at least one follow-up scan (n=1958), overall area under the receiver operating characteristic curve ranged from 0.76 (95% confidence interval 0.66 to 0.84) for RMI to 0.89 (0.81 to 0.94) for ADNEX with CA125. CONCLUSIONS: Our study found the ADNEX models and SRRisk are the best models to distinguish between benign and malignant masses in all patients presenting with an adnexal mass, including those managed conservatively. TRIAL REGISTRATION: ClinicalTrials.gov NCT01698632.


Assuntos
Neoplasias das Tubas Uterinas/diagnóstico , Neoplasias das Tubas Uterinas/patologia , Modelos Logísticos , Neoplasias Ovarianas/diagnóstico , Neoplasias Ovarianas/patologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Antígeno Ca-125/sangue , Calibragem , Tratamento Conservador , Neoplasias das Tubas Uterinas/terapia , Feminino , Humanos , Proteínas de Membrana/sangue , Pessoa de Meia-Idade , Neoplasias Ovarianas/terapia , Ovariectomia , Estudos Prospectivos , Medição de Risco/métodos , Ultrassonografia , Adulto Jovem
9.
Water Sci Technol ; 81(11): 2422-2431, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784285

RESUMO

This paper presents a methodology based on Bayesian networks (BN) to prioritize and select the minimal number of variables that allows predicting the structural condition of sewer assets to support the strategies in proactive management. The integration of BN models, statistical measures of agreement (Cohen's Kappa coefficient) and a statistical test (Wilcoxon test) were useful for a robust and straightforward selection of a minimum number of variables (qualitative and quantitative) that ensure a suitable prediction level of the structural conditions of sewer pipes. According to the application of the methodology to a specific case study (Bogotás sewer network, Colombia), it found that with only two variables (age and diameter) the model could achieve the same capacity of prediction (Cohen's Kappa coefficient = 0.43) as a model considering several variables. Furthermore, the methodology allows finding the calibration and validation percentage subsets that best fit (80% for calibration and 20% for validation data in the case study) in the model to increase the capacity of prediction with low variations. Furthermore, it found that a model, considering only pipes in critical and excellent conditions, increases the capacity of successful predictions (Cohen's Kappa coefficient from 0.2 to 0.43) for the proposed case study.


Assuntos
Gerenciamento de Resíduos , Águas Residuárias , Teorema de Bayes , Calibragem , Colômbia , Análise Custo-Benefício
10.
Nucl Med Commun ; 41(9): 965-976, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32796486

RESUMO

OBJECTIVES: The aim of this study was to characterize national variation in radionuclide calibrator activity response to a single National Institute of Standards and Technology (NIST) traceable reference Ge source used as a surrogate for F at clinical PET centres in England using National Physical Laboratory approved techniques. METHODS: Readings from 20 instruments at 13 centres using local F and Ge factor settings were recorded with the source located in vial and syringe positions. Ten repeat measurements were conducted to investigate repeatability using % coefficient of variability (COV). Comparison ratios to investigate accuracy were made between calibrator responses and decay-corrected NISTref reference activity for syringe and vial position measurements. RESULTS: The maximum %COV was 0.79%, while 90, 95 and 80% of calibrators conformed to 5% accuracy for F syringe, Ge syringe and Ge vial position readings, respectively. We revealed a trend towards reduced bias in measurements using Veenstra devices for F and using Capintec devices for Ge factor settings. CONCLUSIONS: This study demonstrated good repeatability in local device measurements. In total, 70% of English calibrators tested and 88% of all measurements performed achieved 5% accuracy. While statistically significant bias was exhibited between different vendor equipment dependent upon radioisotope selected, our study recommends regular traceability checks for optimum instrument performance conducted within National Metrology Institutes guidelines.


Assuntos
Germânio , Tomografia por Emissão de Pósitrons/normas , Radioisótopos , Compostos Radiofarmacêuticos/análise , Algoritmos , Calibragem , Inglaterra , Radioisótopos de Flúor/análise , Humanos , Imagens de Fantasmas , Padrões de Referência , Reprodutibilidade dos Testes , Seringas
11.
J Chromatogr A ; 1626: 461377, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797853

RESUMO

This study reports the use ofa natural deep eutectic solvent (NADES) with hollow fiber-microporous membrane liquid-liquid microextraction (HF-MMLLE) for the multiclass determination of 11 compounds classified as emerging contaminantsin water. Different deep eutectic solvents were synthetized and Thymol: Camphor (1:1 molar fraction) wasused as extraction solvent. The Thymol:Camphor was impregnated into the polypropylene membrane porous for 10 min, replacing commonly used solvents (ex. hexane and octanol). The optimized parameters were obtained by multi and univariate models. Extractions were carried out for 50 min using 1.5 mL of water sample at pH 6 and without addition of salt while desorption was made in a mixture of acetone: methanol (3:1, v/v) for 15 min. Separation/quantification was conducted by HPLC with a diode array detection (DAD)and calibration curves were obtained for each analyte. Determination coefficients higher than 0.9906 and limits of detection ranged from 0.3 to 6.1 µg L-1. Intraday precision (n = 3) ranged from 1.6 to 18.4% and inter day from 5.0 to 21.3%. Relative recoveries were performed in tap and stream water and ranged from 64 to 123%.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Microextração em Fase Líquida/métodos , Solventes/química , Poluentes Químicos da Água/análise , Calibragem , Cromatografia Líquida de Alta Pressão/normas , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais , Polipropilenos/química , Porosidade , Espectrofotometria , Poluentes Químicos da Água/isolamento & purificação , Poluentes Químicos da Água/normas
12.
J Chromatogr A ; 1626: 461347, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797827

RESUMO

Phthalate diesters are a group of plasticizers extensively used in the manufacturing and processing of plastics. Phthalate monoesters are the primary degradation products of the diesters. Accumulation of endocrine disruptive diesters and monoesters in soil is of great concern because of the extensive use of plastic mulching and misdisposal of plastics. Accurate determination of their levels in soil is critical to assess the occurrence, exposure, and risks of phthalate diesters and monoesters. In this study, we aimed to develop a robust and environmentally friendly method for the simultaneous determination of phthalate diesters and monoesters in soil. Ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry was used for quantification, combined with accelerated solvent extraction and in-line cleanup for sample preparation. The method detection limits for the 14 diesters and 11 monoesters were in the range of 0.59 to 10.08 ng g-1 d.w. Acceptable recoveries (69%-131%) for these analytes were obtained when four deuterated analogs were used for internal calibration, and intra- and inter-day variations were less than 15%. This method was later successfully applied to five soil samples, and 8 diesters and 7 monoesters were detected with the maximum concentration up to 1142.2 ng g-1 d.w. The method developed in this study can be used for screening and accurate quantification of phthalate diesters and monoesters in soil and possibly in other environmental matrices.


Assuntos
Ácidos Ftálicos/análise , Plastificantes/análise , Solo/química , Calibragem , Cromatografia Líquida de Alta Pressão/normas , Disruptores Endócrinos/análise , Disruptores Endócrinos/normas , Ésteres/química , Limite de Detecção , Ácidos Ftálicos/química , Ácidos Ftálicos/normas , Plastificantes/normas , Espectrometria de Massas em Tandem/normas , Temperatura
13.
J Environ Manage ; 274: 111191, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32798849

RESUMO

Sulphide is one of the inhibitors in the nitrification process in WWTP in regions with sulphate rich soils. As little information is currently available on sulphide nitrification inhibition, the aim of this study was to develop a method based on a modification of the Successive Additions Method to calibrate the effect of sulphide on the activity of ammonia-oxidising bacteria (AOB) and nitrite-oxidising bacteria (NOB). The developed method was then applied to activated sludge samples from two WWTPs with different influent sulphide concentrations. In both cases, sulphide had a greater inhibitory effect on NOB than AOB activity. The sulphide inhibition was found to be lower in the activated sludge fed with sulphide-rich wastewater. The AOB and NOB activity measured at different sulphide concentrations could be accurately modelled with the Hill inhibition equation.


Assuntos
Amônia , Nitrificação , Reatores Biológicos , Calibragem , Nitritos , Oxirredução , Esgotos , Sulfetos
14.
Cochrane Database Syst Rev ; 7: CD012022, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32735048

RESUMO

BACKGROUND: Chronic lymphocytic leukaemia (CLL) is the most common cancer of the lymphatic system in Western countries. Several clinical and biological factors for CLL have been identified. However, it remains unclear which of the available prognostic models combining those factors can be used in clinical practice to predict long-term outcome in people newly-diagnosed with CLL. OBJECTIVES: To identify, describe and appraise all prognostic models developed to predict overall survival (OS), progression-free survival (PFS) or treatment-free survival (TFS) in newly-diagnosed (previously untreated) adults with CLL, and meta-analyse their predictive performances. SEARCH METHODS: We searched MEDLINE (from January 1950 to June 2019 via Ovid), Embase (from 1974 to June 2019) and registries of ongoing trials (to 5 March 2020) for development and validation studies of prognostic models for untreated adults with CLL. In addition, we screened the reference lists and citation indices of included studies. SELECTION CRITERIA: We included all prognostic models developed for CLL which predict OS, PFS, or TFS, provided they combined prognostic factors known before treatment initiation, and any studies that tested the performance of these models in individuals other than the ones included in model development (i.e. 'external model validation studies'). We included studies of adults with confirmed B-cell CLL who had not received treatment prior to the start of the study. We did not restrict the search based on study design. DATA COLLECTION AND ANALYSIS: We developed a data extraction form to collect information based on the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Independent pairs of review authors screened references, extracted data and assessed risk of bias according to the Prediction model Risk Of Bias ASsessment Tool (PROBAST). For models that were externally validated at least three times, we aimed to perform a quantitative meta-analysis of their predictive performance, notably their calibration (proportion of people predicted to experience the outcome who do so) and discrimination (ability to differentiate between people with and without the event) using a random-effects model. When a model categorised individuals into risk categories, we pooled outcome frequencies per risk group (low, intermediate, high and very high). We did not apply GRADE as guidance is not yet available for reviews of prognostic models. MAIN RESULTS: From 52 eligible studies, we identified 12 externally validated models: six were developed for OS, one for PFS and five for TFS. In general, reporting of the studies was poor, especially predictive performance measures for calibration and discrimination; but also basic information, such as eligibility criteria and the recruitment period of participants was often missing. We rated almost all studies at high or unclear risk of bias according to PROBAST. Overall, the applicability of the models and their validation studies was low or unclear; the most common reasons were inappropriate handling of missing data and serious reporting deficiencies concerning eligibility criteria, recruitment period, observation time and prediction performance measures. We report the results for three models predicting OS, which had available data from more than three external validation studies: CLL International Prognostic Index (CLL-IPI) This score includes five prognostic factors: age, clinical stage, IgHV mutational status, B2-microglobulin and TP53 status. Calibration: for the low-, intermediate- and high-risk groups, the pooled five-year survival per risk group from validation studies corresponded to the frequencies observed in the model development study. In the very high-risk group, predicted survival from CLL-IPI was lower than observed from external validation studies. Discrimination: the pooled c-statistic of seven external validation studies (3307 participants, 917 events) was 0.72 (95% confidence interval (CI) 0.67 to 0.77). The 95% prediction interval (PI) of this model for the c-statistic, which describes the expected interval for the model's discriminative ability in a new external validation study, ranged from 0.59 to 0.83. Barcelona-Brno score Aimed at simplifying the CLL-IPI, this score includes three prognostic factors: IgHV mutational status, del(17p) and del(11q). Calibration: for the low- and intermediate-risk group, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of four external validation studies (1755 participants, 416 events) was 0.64 (95% CI 0.60 to 0.67); 95% PI 0.59 to 0.68. MDACC 2007 index score The authors presented two versions of this model including six prognostic factors to predict OS: age, B2-microglobulin, absolute lymphocyte count, gender, clinical stage and number of nodal groups. Only one validation study was available for the more comprehensive version of the model, a formula with a nomogram, while seven studies (5127 participants, 994 events) validated the simplified version of the model, the index score. Calibration: for the low- and intermediate-risk groups, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of the seven external validation studies for the index score was 0.65 (95% CI 0.60 to 0.70); 95% PI 0.51 to 0.77. AUTHORS' CONCLUSIONS: Despite the large number of published studies of prognostic models for OS, PFS or TFS for newly-diagnosed, untreated adults with CLL, only a minority of these (N = 12) have been externally validated for their respective primary outcome. Three models have undergone sufficient external validation to enable meta-analysis of the model's ability to predict survival outcomes. Lack of reporting prevented us from summarising calibration as recommended. Of the three models, the CLL-IPI shows the best discrimination, despite overestimation. However, performance of the models may change for individuals with CLL who receive improved treatment options, as the models included in this review were tested mostly on retrospective cohorts receiving a traditional treatment regimen. In conclusion, this review shows a clear need to improve the conducting and reporting of both prognostic model development and external validation studies. For prognostic models to be used as tools in clinical practice, the development of the models (and their subsequent validation studies) should adapt to include the latest therapy options to accurately predict performance. Adaptations should be timely.


Assuntos
Leucemia Linfocítica Crônica de Células B/mortalidade , Modelos Teóricos , Adulto , Fatores Etários , Viés , Biomarcadores Tumorais , Calibragem , Intervalos de Confiança , Análise Discriminante , Intervalo Livre de Doença , Feminino , Genes p53/genética , Humanos , Cadeias Pesadas de Imunoglobulinas/genética , Região Variável de Imunoglobulina/genética , Leucemia Linfocítica Crônica de Células B/patologia , Masculino , Estadiamento de Neoplasias , Prognóstico , Intervalo Livre de Progressão , Receptores de Antígenos de Linfócitos B/genética , Reprodutibilidade dos Testes , Proteína Supressora de Tumor p53/genética
15.
J Chromatogr A ; 1625: 461309, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709351

RESUMO

The adsorption behavior of the model proteins: alpha-Lactalbumin, Bovine Serum Albumin, Lysozyme, and a monoclonal antibody, in single component and in binary mixtures, was investigated on two different hydrophobic interaction chromatography resins using both static and dynamic methods. A kinetic model of the adsorption process was developed, which accounted for protein unfolding and intermolecular interactions in the adsorbed phase. The latter incorporated positive cooperative interactions, resulting from preferred and multilayer adsorption on the adsorbent surface, as well as negative cooperative interactions attributed to exclusion effects due to size exclusion and repulsion. Cooperative adsorption resulted in negative or positive deviations from the Langmuir model for both single and multicomponent isotherms. The model was used to assess possible contributions of different adsorption mechanisms of proteins and their structurally different forms to the overall adsorption pattern, as well as to simulate chromatographic band profiles under different loading conditions. For proteins with unstable structure, the overall adsorption isotherm was dominated by binding of unfolded species at low surface coverage and by positive cooperative adsorption at high surface coverage. Furthermore, regardless of structural stability, exclusion effects influenced strongly adsorption equilibrium, particularly at low surface coverages. In case of chromatographic elution, i.e. under dynamic conditions, unfolding, negative cooperative adsorption, and kinetic effects governed the retention behavior and determined peak shapes, whereas the effect of positive cooperative adsorption was negligible.


Assuntos
Cromatografia/métodos , Interações Hidrofóbicas e Hidrofílicas , Proteínas/isolamento & purificação , Adsorção , Animais , Calibragem , Galinhas , Cinética , Lactalbumina/isolamento & purificação , Muramidase/isolamento & purificação , Ligação Proteica , Soroalbumina Bovina/isolamento & purificação , Temperatura
16.
J Chromatogr A ; 1625: 461325, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709354

RESUMO

We derive a model of band broadening in multiple-open-tubular columns enabling transverse diffusion (MOTTD). In MOTTD columns, the flow channels are straight, parallel, cylindrical tubes arranged in a hexagonal compact array. A mesoporous material or stationary phase (130 Å bridged-ethyl hybrid (BEH) silica support) is filling the volume between the flow channels. The model is based on Giddings' random-walk theory of non-equilibrium chromatography. It is calibrated for the unknown configuration factor, qs, related to the specific geometry of the stationary phase in MOTTD columns. qs values are found based on the best fit of the model to simulated dispersion data obtained by the lattice-Boltzmann method for modelling fluid flow and a random-walk particle-tracking technique to address advective-diffusive transport of the analytes. For the model calibration, simulations are performed for different ratios, ρ, of the average inner diameter of the flow channels to their closest center-to-center distance under retained and non-retained conditions. The model is successfully validated (average relative errors below 10%) under both retained and non-retained conditions. For the same column format (4.6 mm i.d.  ×  150 mm), external porosity, zone retention factor, and relative standard deviation of the distribution of the inner diameters of the flow channels, the derived model reveals the intrinsic advantage of MOTTD columns (center-to-center distance between flow channels of 5 µm and ρ = 0.62) over a conventional column packed with 5 µm 130 Å BEH silica particles and the same multiple porous-layer open-tubular column (MPLOT) disabling transverse dispersion. MOTTD columns are weakly affected by the polydispersity of the inner diameter of the flow channels. Provided MOTTD columns could be prepared at a small feature size of 5 µm or less, they are expected to deliver a significant improvement in column technology relative to current particulate and silica monolithic columns.


Assuntos
Cromatografia/métodos , Modelos Químicos , Calibragem , Simulação por Computador , Difusão , Porosidade , Reprodutibilidade dos Testes , Dióxido de Silício/química
17.
J Chromatogr A ; 1625: 461267, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709320

RESUMO

We describe the design and performance evaluation of a portable gas chromatograph suitable for the analysis of volatile organic and odorous compounds at trace levels. The system comprises a carbon nanotube sponge preconcentrator, an electronic pressure control (EPC) unit, a temperature-programmable column module, and a fast-response photoionization detector. A built-in tablet computer controls instrumental parameters and chromatogram display functions. The compact GC with dimensions of 35 cm (l) × 26 cm (w) × 15 cm (h) is self-contained, weighing less than 5 kg without a battery pack, and uses no auxiliary compressed gases. Our design has three main advantages over conventional portable GCs: recharging configuration of ambient air as the carrier gas using a miniature diaphragm pump, precise control of column flow by the built-in canister and EPC system, and rapid thermal desorption of the preconcentrator facilitated by intrinsic resistivity of the carbon nanotube sponge. A 30 m, 0.28 mm I.D. capillary column operated at a head pressure of 14 psi provided a peak capacity of 55 for a 10 min isothermal analysis. The temperature-programmability feature could decrease the analysis time of less than 5 min for vapor mixture of benzene, toluene, ethylbenzene, and o-xylene. More than a 100-fold increase in sensitivity by preconcentrating a sample adsorption volume of 90 mL resulted in improved detection limits of 0.13 (benzene), 0.20 (toluene), 0.23 (ethylbenzene), and 0.28 (o-xylene) ppb (v/v). Our instrument displayed good stability and reproducibility of retention times (< 0.14% RSD) and intensities (< 4.5% RSD) for continuous measurements using the preconcentrator over 10 h. Thus, continuous and on-site determinations of trace volatile organic compounds in air samples with this instrument appear feasible.


Assuntos
Poluentes Atmosféricos/análise , Cromatografia Gasosa/métodos , Sistemas Computacionais , Hidrocarbonetos Aromáticos/análise , Compostos Orgânicos Voláteis/análise , Calibragem , Gases/análise , Limite de Detecção , Nanotubos de Carbono/química , Odorantes/análise , Pressão , Reprodutibilidade dos Testes , Temperatura , Fatores de Tempo
18.
Toxicol Lett ; 332: 36-41, 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-32629075

RESUMO

The study examined the degradation of riot control agents (RCAs): 2-chloroacetophenone (CN), 2-chlorobenzalmalononitrile (CS), and capsaicin, using the Reactive Skin Decontamination Lotion Kit (RSDL®) lotion and evaluated the the direct liquid phase reactivity of the RSDL lotion component with each RCA. RSDL lotion was mixed with the selected RCAs at different molar ratios. Reactivity of the active ingredient potassium 2,3-butanedione monoximate (KBDO) with the RCA was observed for one hour. Samples of 10 µL were taken and quenched, analyzed for residual RCA using LC-MS. CN, was degraded at molar ratios of two and above in less than 2 min. At a molar ratio of 1:1 KBDO:CN, ∼90 % of CN was degraded within 2 min, the remaining 10 % residual CN was observed for one hour without any change. CS, degradation of more than 68 % of CS was achieved at 20:1 M ratio of KBDO:CS within 1 h of reaction time. For capsaicin, no degradation was observed regardless of the higher molar ratios of up to 20:1 and longer reaction times of up to one hour. This study provides evaluation of neutralizing action of the RSDL lotion without assessment of the physical removal component by the RSDL Kit.


Assuntos
Capsaicina/isolamento & purificação , Descontaminação/métodos , Irritantes/isolamento & purificação , Fármacos do Sistema Sensorial/isolamento & purificação , Pele/química , ômega-Cloroacetofenona/isolamento & purificação , Calibragem , Capsaicina/análise , Substâncias para a Guerra Química , Cromatografia Líquida de Alta Pressão , Humanos , Irritantes/análise , Fármacos do Sistema Sensorial/análise , ômega-Cloroacetofenona/análise
20.
Br J Radiol ; 93(1114): 20200228, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32726141

RESUMO

OBJECTIVES: Software re-calculation of proton pencil beam scanning plans provides a method of verifying treatment planning system (TPS) dose calculations prior to patient treatment. This study describes the implementation of AutoMC, a Geant4 v10.3.3/Gate v8.1 (Gate-RTion v1.0)-based Monte-Carlo (MC) system for automated plan re-calculation, and presents verification results for 153 patients (730 fields) planned within year one of the proton service at The Christie NHS Foundation Trust. METHODS: A MC beam model for a Varian ProBeam delivery system with four range-shifter options (none, 2 cm, 3 cm, 5 cm) was derived from beam commissioning data and implemented in AutoMC. MC and TPS (Varian Eclipse v13.7) calculations of 730 fields in solid-water were compared to physical plan-specific quality assurance (PSQA) measurements acquired using a PTW Octavius 1500XDR array and PTW 31021 Semiflex 3D ion chamber. RESULTS: TPS and MC showed good agreement with array measurements, evaluated using γ analyses at 3%, 3 mm with a 10% lower dose threshold:>94% of fields calculated by the TPS and >99% of fields calculated by MC had γ ≤ 1 for>95% of measurement points within the plane. TPS and MC also showed good agreement with chamber measurements of absolute dose, with systematic differences of <1.5% for all range-shifter options. CONCLUSIONS: Reliable independent verification of the TPS dose calculation is a valuable complement to physical PSQA and may facilitate reduction of the physical PSQA workload alongside a thorough delivery system quality assurance programme. ADVANCES IN KNOWLEDGE: A Gate/Geant4-based MC system is thoroughly validated against an extensive physical PSQA dataset for 730 clinical fields, showing that clinical implementation of MC for PSQA is feasible.


Assuntos
Terapia com Prótons/métodos , Garantia da Qualidade dos Cuidados de Saúde , Planejamento da Radioterapia Assistida por Computador , Algoritmos , Calibragem , Inglaterra , Humanos , Método de Monte Carlo , Dosagem Radioterapêutica , Reprodutibilidade dos Testes
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