SIM Method Research Articles

N-AlKanes Base Exploration as Potential Petroleum Source Rocks in ILullemmeden Basin (Sokoto Basin) North west Nigeria

The aim of this work is to investigate the potential petroleum shales of Dukamaje formation in Sokoto basin for their petroleum potentials. A total of sixteen samples were obtained from different parts of the basin. The samples were subjected to sohxlet extraction to extract the bitumen. The bitumen was subjected to column chromatography and aliphatic and aromatic fractions were collected from each sample by using DCM and n-hexane as solvents. The fractions were subjected to GC/MS analyses with the application of SIM method (selected ion monitoring) which revealed the wide variety of hydrocarbons compounds including n-alkanes, hopanes, sterenes, phenanthrenes, methyl-phenanthrenes and triaromatic steroids. Interpretation biomarker parameters revealed that the rocks under studies are endowed with organic matter. Also biomarker correlation parameters were employed to compute the quantity of organic matter, type of organic matter, thermal maturity of the organic matter and to assess the depositional environment of the rocks samples. The biomarker parameters indicated that the source organic matter is mostly from marine environment, the depositional condition found to be anoxic reducing condition. The shales are reach in organic matter and the shales are found to be partially matured.

Quality Control of Oleum Cinnamomi Assisted by Network Pharmacology Strategy.

Oleum Cinnamomi is a traditional medicine used by the Hmong, the essential oil obtained from Fructus Cinnamomi, for the treatment of coronary heart disease. Information regarding the efficient quality control markers of it is lacking, which has become a bottleneck restricting its development and utilization. Here, an integrated qualitative analysis approach based on a GC-MS and network pharmacology strategy was applied to explore quality control markers for the assessment of Oleum Cinnamomi. Firstly, the compounds of Oleum Cinnamomi were detected by GC-MS. In total, 57 chemical components were identified, mainly monoterpenes and sesquiterpenes, accounting for 83.05% of total essential oil components. Secondly, network pharmacology was adopted to explore the compounds linked to target genes of coronary heart disease. Fifty-two compounds were found, indicating the effectiveness of Oleum Cinnamomi in the treatment of coronary heart disease. Among them, 10 compounds, including eucalyptol, were chosen as potential effective compounds in Oleum Cinnamomi. Thirdly, an established GC-MS SIM method was validated and applied for the simultaneous determination of the contents of these 10 compounds using 20 sample batches of Oleum Cinnamomi. It was preliminarily found that the contents of these 10 compounds differed in Oleum Cinnamomi from different origins. Finally, quantitative analyte data were analyzed using multivariate statistical analysis to determine Oleum Cinnamomi quality. Four compounds (eucalyptol, p-cymene, sabinene, β-pinene) were identified as chemical markers for quality control. Accordingly, this study provides new strategies to explore the quality control markers and develops a novel method for the quality assessment of Oleum Cinnamomi.

Analisis Portofolio Optimal CAPM dan Single Index Model pada Perusahaan IDX30

The purpose of this study is to analyze the optimal stock portfolio using the Capital Asset Pricing Model and Single Index Model, then look at the portfolio performance formed on IDX30 stocks for the period February 2017 – July 2021 with a sample of 16 stocks. This research includes quantitative descriptive. The results showed: (1) CAPM method, obtained 2 stocks, namely: BBCA and ICBP. With a portfolio return rate of 0.26%, and a portfolio risk level of 5.32%. (2) SIM method, only one share is obtained, namely: BBCA. With a portfolio return rate of 1.38%, and a portfolio risk level of 0.57%. (3) the performance of the CAPM portfolio is worth 0.0485 Sharpe index, 0.0034 Treynor, and 0.00515 Jensen. (4) SIM portfolio performance has an index of Sharpe 2.4280, Treynor 0.0154, and Jensen 0.01690. (5) stock performance in CAPM, namely BBCA and ICBP with Sharpe indexes 1.09286 and 0.17500, Treynor 0.00342 and 0.00319, and Jensen 0.00615 and 0.00116. (6) stock performance on SIM, namely BBCA with Sharpe index of 0.07857, Treynor 0.00025, and Jensen 0.00331

Identification of Influential Nodes in Industrial Networks Based on Structure Analysis

Industrial network systems are facing various new challenges, such as increasing functional failure factors, the accelerating penetration of information threats, and complex and diverse attack methods. Industrial networks are often vulnerable to natural or intentional disasters; therefore, it is highly invaluable to research to identify the influential nodes. Most of the state-of-the-art evaluates the importance of the nodes according to one or more network metrics. Moreover, there are no metrics reflecting all the properties of the network. In this paper, a novel method (Structure-based Identification Method, SIM) to identify the influential nodes in industrial networks is proposed based on the network structure, which goes beyond the use of network metrics. The SIM method extracts the weakly connected components, which are more likely to survive after the important nodes are attacked in the network. Evaluation results show that the SIM method obtains better results than the state-of-the-art methods to identify influential nodes in real-world industrial networks and has a good prospect to be applied in industrial application.

Textile Museum Collections. SIM Method Validation for the Assessment of Pesticides

In time the environmental conditions could damage textiles (materials/ artifacts) causing the need to develop better non-destructive or at least micro-destructive analysis techniques of the samples. There are ethnographic textile artifacts that were treated in the past with various pesticides, that have not been mentioned in any document. These are often re-treated with chemicals by museum staff as a method of preventing pest infestation. Due to the progressive use of many pesticides, this paper was focused on the detection and quantification of three pesticides: malathion, methoxychlor, and permethrin (cis- and trans- isomers). Gas chromatography is one of the most widely used analytical techniques for characterizing volatile organic compounds and therefore was the analytical method of choice for the present study. Because these analytes are found at trace levels, the detection and quantification limits of analytes are very small and it is necessary to optimize and validate a SIM method - that allows the mass spectrometer to detect specific compounds with high sensitivity. In SIM mode, the instrument is set to collect data at selected masses of interest, thus increasing the accuracy and precision of the quantitative results. The present paper is aimed to develop this type of method with specificity and selectivity, high precision (expressed in terms of repeatability and intermediate accuracy), accuracy, suitable working range and linearity, and high degree of series� homogenity.

Development and Validation of a GC-MS with SIM Method for the simultaneous estimation of 13 docosenamide, n-tetracosanol-1 and squalene from the leaf extracts of Wagatea spicata

Development and Validation of a GC-MS with SIM Method for the simultaneous estimation of 13 docosenamide, n-tetracosanol-1 and squalene from the leaf extracts of Wagatea spicata

Simultaneous phase-inversion and crosslinking in organic coagulation bath to prepare organic solvent forward osmosis membranes

Organic solvent forward osmosis (OSFO) is an emerging separation process, which can realize simultaneous concentration of pharmaceutical ingredients and solvent recovery. In this work, a time-saving preparation process for solvent-resistant support layers was proposed by a simultaneous phase-inversion and crosslinking (SIM) method. The SIM method combines the formation of porous polyimide (PI) support layer and crosslinking between the PI and hexanediamine (HDA) in the coagulating baths, thus avoiding an extra need of solvent-based synthesis step. Furthermore, isopropanol (IPA) was used as coagulation bath for solvent-resistant PI support layers preparation, which can more effectively retarding the phase-inversion process compared with the DI-water. In addition, the morphologies and properties of these support layers with different synthesis time were prepared and characterized. After interfacial polymerization reaction using the as-prepared solvent-resistant PI support layers, the resultant OSFO membranes exhibited reasonable ethanol fluxes, lower reverse salt fluxes, and excellent pharmaceutical (oxytetracycline, OTC) rejections in both forward and reverse osmosis modes. Moreover, the long-term tests of as-prepared OSFO membranes indicated an excellent stability in 10 h operation with ethanol. After 10 h activation using DMF, the ethanol fluxes of OSFO18h membranes with different thickness of solvent-resistant support layers were significantly improved without sacrificing OTC rejection, which furtherly demonstrated the timeliness of SIM method and potential application of OSFO process in both concentrate the pharmaceutical and solvent recovery.

Evaluation of Extrapolation Methods to Predict Trough Concentrations to Guide Therapeutic Drug Monitoring of Oral Anticancer Drugs.

For oral anticancer drugs, trough concentration (Cmin) is usually used as a target in therapeutic drug monitoring (TDM). Recording of Cmin is highly challenging in outpatients, in whom there is typically a variability in sample collection time after dosing. Various methods are used to estimate Cmin from the collected samples. This simulation study aimed to evaluate the performance of 3 different methods in estimating the Cmin of 4 oral anticancer drugs for which TDM is regularly performed. Plasma concentrations of abiraterone, dabrafenib, imatinib, and pazopanib at a random time (Ct,sim) and at the end of the dosing interval (Cmin,sim) were simulated from population pharmacokinetic models including 1000 patients, and the values were converted into simulated observed concentrations (Ct,sim,obs and Cmin,sim,obs) by adding a residual error. From Ct, sim,obs, Cmin was predicted (Cmin,pred) by the Bayesian estimation (method 1), taking the ratio of the Ct,sim,obs and typical population concentration and multiplying this ratio with the typical population value of Cmin,sim (method 2), and log-linear extrapolation (method 3). Target attainment was assessed by comparing Cmin,pred with the proposed pharmacokinetic targets related to efficacy and calculating the positive predictive and negative predictive values. The mean relative prediction error and root mean squared relative prediction error results showed that method 3 was out-performed by method 1 and 2. Target attainment was adequately predicted by all 3 methods (the respective positive predictive value of method 1, 2, and 3 was 92.1%, 92.5%, and 93.1% for abiraterone; 87.3%, 86.9%, and 99.1% for dabrafenib; 79.3%, 79.3%, and 75.9% for imatinib; and 72.5%, 73.5%, and 67.6% for pazopanib), indicating that dose adjustments were correctly predicted. Both method 1 and 2 provided accurate and precise individual Cmin,pred values. However, method 2 was easier to implement than method 1 to guide individual dose adjustments in TDM programs.

Detection of quantitative genes controlling of chlorophyll content in rice seedling under normal and salinity stress and comparison of different QTL mapping methods

شوری یک محدودیت عمده در توسعه کشت برنج می‌باشد. بهبود بخشیدن به تحمل به شوری در برنج ازنظر ژنتیکی یک مسئله بسیار مهم در برنامه‌های اصلاحی است. به‌منظور مکان یابی ژن های کنترل کننده محتوای کلروفیل، 96 لاین خالص نوترکیب برنج ایرانی حاصل تلاقی ارقام ندا × اهلمی-طارم تحت تنش شوری در مرحله گیاهچه‌ای آزمایشی به‌صورت مرکب در قالب طرح کاملا تصادفی با سه تکرار و دو شرایط کشت نرمال و تنش شوری در دانشگاه گنبد‌کاووس در سال 1395 در شرایط گیاهچه کشت شدند. مکان‌یابی ژن‌های کنترل‌کننده محتوای کلروفیل با استفاده از روش‌های مختلف مکان‌یابی شامل SIM-MEL، SIM، CIM، MIM، PMLE، ICIM و STSIM انجام گرفت و با استفاده از هر کدام از این روش‌ها QTL‌های مشابه و متفاوتی ردیابی شد. 40 نشانگر SSR و 16 نشانگر ISSR (76 آلل تکثیر‌شده چند شکل)، 2 نشانگر IRAP (7 آلل تکثیر‌شده چند شکل) و یک نشانگر iPBS (3 آلل تکثیر‌شده چند شکل) بر روی 12 کروموزوم برنج توزیع شدند. روش ICIM، CIM و SIM در شرایط نرمال و تنش شوری بیشترین تشابه مکان‌های ژنی ردیابی شده را دارا بودند. qCHL-6 در شش روش مکان‌یابی در موقعیت 52 سانتی‌مورگان از کروموزوم 6 شناسایی شد. بنابراین با استفاده از QTL‌های شناسایی شده می‌توان پس از تعیین اعتبار QTLها، ژنوتیپ‌های برتر از نظر محتوای کلروفیل برای برنامه‌های انتخاب به کمک نشانگر را شناسایی کرد.

Radiotherapy dose distribution prediction for breast cancer using deformable image registration

BackgroundRadiotherapy treatment planning dose prediction can be used to ensure plan quality and guide automatic plan. One of the dose prediction methods is incorporating historical treatment planning data into algorithms to estimate the dose–volume histogram (DVH) of organ for new patients. Although DVH is used extensively in treatment plan quality and radiotherapy prognosis evaluation, three-dimensional dose distribution can describe the radiation effects more explicitly. The purpose of this retrospective study was to predict the dose distribution of breast cancer radiotherapy by means of deformable registration into atlas images with historical treatment planning data that were considered to achieve expert level. The atlas cohort comprised 20 patients with left-sided breast cancer, previously treated by volumetric-modulated arc radiotherapy. The registration-based prediction technique was applied to 20 patients outside the atlas cohort. This study evaluated and compared three different approaches: registration to the most similar image from a dataset of individual atlas images (SIM), registration to all images from a database of individual atlas images with the average method (WEI_A), and the weighted method (WEI_F). The dose prediction performance of each strategy was quantified using nine metrics, including the region of interest dose error, 80% and 100% prescription area dice similarity coefficients (DSCs), and γ metrics. A Friedman test and a nonparametric exact Wilcoxon signed rank test were performed to compare the differences among groups. The clinical doses of all cases served as the gold standard.ResultsThe WEI_F method could achieve superior dose prediction results to those of WEI_A. WEI_F outperformed SIM in the organ-at-risk mean absolute difference (MAD). When using the WEI_F method, the MAD values for the ipsilateral lung, heart, and whole lung were 197.9 ± 42.9, 166 ± 55.1, 122.3 ± 25.5, and 55.3 ± 42.2 cGy, respectively. Moreover, SIM exhibited superior prediction in the DSC and γ metrics. When using the SIM method, the means of the 80% and 100% prescription area DSCs, 33γ metric, and 55γ metric were 0.85 ± 0.05, 0.84 ± 0.05, 0.64 ± 0.13, and 0.84 ± 0.10, respectively. The plan target volume and spinal cord MAD when using SIM and WEI were 235.6 ± 158.4 cGy versus 227.4 ± 144.0 cGy (p > 0.05) and 61.4 ± 44.9 cGy versus 55.3 ± 42.2 cGy (p > 0.05), respectively.ConclusionsA predicted dose distribution that approximated the clinical plan could be generated using the methods presented in this study.

Inheritance of faba bean resistance to Broomrape, genetic diversity and QTL mapping analysis.

Six faba bean parents and their F1 and F2 generations were used in this investigation to study the genetic system controlling resistance of faba bean (Vicia faba L.) to broomrape (Orobanche crenata). Most of the F1 hybrids were tolerant to broomrape. In the F2 generation, the population P5×P6 (Assiut 125 × Romy 12) gave the highest value of relative yield and tolerance index. Heterosis and inbreeding depression were only positive in number of tillers/plant and seed yield/plant characters. The results indicated that the additive effect was more important than the dominance one (D>H1) only for No. of pods/plant in the F1 generation. Moreover, the narrow-sense heritability was low for most of the studied traits. Three molecular marker systems, namely RAPD, ISSR and SRAP were used for identification and estimation of the genetic diversity among the six faba bean genotypes. The three molecular markers generated DNA unique bands for all genotypes. Only, eight DNA fragments were related to Orobanche tolerance. Clearly and reproducible polymorphic markers were subjected to QTL analysis. The linkage analysis showed that, out of 34 marker loci segregated in the F2 population, 29 (85.29%) were mapped on three linkage groups. QTL analysis using SIM method performed for the 29 markers assigned to LG-1, LG-2 and LG-3 with the eight traits, number of tillers/plant, plant height, number of pods/plant, seed yield/plant, number of broomrape spikes per plant, height of broomrape spikes, relative yield and tolerance index, showing 12 putative QTLs for all traits except number of tillers/plant. From this study, it is clear that P5×P6 (Assiut 125 × Romy12) population could be considered promising for selection for resistance to broomrape infestation.

Classifying the integrated public safety areas (IPSAs): a multi-criteria based approach

PurposeThis study aims to focus on the application of a multiple criteria decision analysis (MCDA) method to compare results presented by the Integrated Goals System based on the 12th edition of the Integrated Public Safety Areas (IPSAs) Award, which achieved goals established for Strategic Crime Indicators for the state of Rio de Janeiro, Brazil. The main objective of this research was to limit the compensatory effects of classification criteria on IPSAs that have achieved goals established for crime indicators by applying the MCDA method.Design/methodology/approachThe methodology was based on the application of MCDA. The MCDA method selected and used was ELECTRE III, being implemented by J-Electre software.FindingsCompared to results of the current method, the results of the ELECTRE III method showed a 94.87 per cent change in ranking positions revealed via the SIM method. This finding denotes the elimination of compensatory effects of the criteria. As a consequence, it can be affirmed that the application of resources by IPSA managers to reduce the prevalence of a single strategic crime indicator is no longer a success factor for awarding in the established goal system.Research limitations/implicationsAs limitations, it is possible to indicate the time cut used to carry out the research. The research may be extended to other issues of the productivity award.Practical implicationsThe methodology applied with the use of ELECTRE III revealed that the government could reduce the cost with the incentive program to reduce criminal indices.Social implicationsAs the MCDA method is based on a binary pairwise comparison system, the methodology imposes a change of attitude on local managers fighting crime to reduce crime indicators and to consequently build a local sense of safety in IPSAs.Originality/valueThis research fills a gap in the literature because there are few studies using the MCDA method in the field of public security. The value of the work lies in the creation of a method that gives the decision-maker, of the law enforcement agency, an alternative to improve the process of rewarding by productividad of the integrated areas of public security.

Accurate Determination of Isotopic Abundance of Intracellular Metabolites of Saccharopolysporaerythraea Based on Ultra Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Abstract A method was established for measuring 13C isotopic abundance of intracellular metabolites of Saccharopolysporaerythraea by ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry. Under the optimized chromatographic conditions of UPLC, and the appropriate and unique tube lens voltage, collision energy and ion pair, one-to-one method, one-to-many method and SIM method were established for measuring 13C isotopic abundance based on the length of the parent and daughter ions carbon chains and whether the daughter ions contain 13C atoms. The three methods were then applied to measure naturally labeled intracellular metabolite standards and 13C labeled samples. According to the gap between the experimental value and the theoretical value, the best method was found for each metabolite of different characteristics. The results showed that one-to-one method was the most effective for measuring the metabolites of daughter ions not containing 13C atoms represented by sugar phosphates, one-to-many method was the best for measuring the metabolites of both parent and daughter ions containing 13C short carbon chains represented by carboxylic acids, SIM method could played a role in measuring the metabolites of both parent and daughter ions containing 13C long carbon chains represented by coenzyme A. These methods had a good measurement precision and could be applied to the measurement of Saccharopolysporaerythraea intracellular metabolites, which would contribute to consequent study of the metabolic mechanism and the efficient expression of erythromycin.

Experimental comparison of approaches for checking completeness of test suites from finite state machines

ContextMany approaches have been proposed for checking test suite completeness for Finite State Machines (FSMs). Some approaches provide sufficient conditions whereas others give necessary and sufficient conditions for test suite completeness. One method, called the CONF method, is based on sufficient conditions, and relies on a search for confirmed sets when checking completeness. If a confirmed set cannot be found, then the outcome is inconclusive. Another method, the SIM method, is based on the notion of simulation relations, and relies on necessary and sufficient conditions when checking test suite completeness. The SIM method always returns conclusive verdicts about suite completeness. ObjectiveIn this work, we describe experimental results comparing these two methods. We also investigate when both methods can be combined for checking completeness of test suites. MethodWe evaluate both strategies according to different parameters of the FSMs, such as the number of states and the number of transitions in the FSM models, the size of input and output alphabets of the FSM models, as well as the size of the test suites. We also report on the relative rates of conclusive and inconclusive verdicts when using both methods. ResultsWe see that these methods are complementary, which allows for a combined strategy: the CONF method is the fastest in terms of processing time, while the SIM method is not as scalable in terms of the size of the specifications. ConclusionThe experimental results indicated a substantial difference for the rate of positive verdicts obtained by the SIM method when compared with the number of positive answers returned by the CONF method.

Otimization of extraction solid phase method for determination of atrazine by gas chromatography

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-striazina), a herbicine from the family of s-triazine, widely used all over the world, has been detected in ground and surface waters in worrying levels of concentration. This compound has a low potential for bioaccumulation, moderate adsorption and mobility in soil. One way 1 Dra.; Fisica; Professora do Colegio Estadual do Parana; Endereco: Avenida Joao Gualberto, 250, Alto da Gloria, CEP: 80030-000, Curitiba, Parana, Brasil; E-mail: crisneiverth@yahoo.com.br Ambiencia Guarapuava (PR) v.11 n.2 p. 475 482 Jan./Abr. 2015 ISSN 1808 0251 Recebido para publicacao em 09/05/2012 e aceito em 16/10/2014 DOI:10.5935/ambiencia.2015.02.14nt Ambiencia Revista do Setor de Ciencias Agrarias e Ambientais V.11 N.2 Jan./Abr. 2015 476 is to determine atrazine is by Gas Chromatography coupled to Mass Spectrometry (CG-MS), using for the sample preparation the extraction in solid phase (SPE), which eliminates interferences and pre-concentrates the sample into a single step. This research aimed to develop a methodology for analysis of atrazine in water using Solid Phase Extraction in Gas Chromatography coupled with the Mass Spectrometry. The recovery was studied at two concentration levels (0.2 and 2.0 mg L-1), comparing the SIM and MS / MS. For quantification, the SIM method showed a better recovery (98% and 105%) and coefficient of variation (1.6%) at a concentration of 2.0 mg L-1. The detection limit of the SIM mode was 0.20 ng L-1 and the method was tested in surface water and leachate water of undisturbed soil columns of three headwaters. Only two samples of leachate water had concentrations of atrazine above those permitted by law (2.0 mg L-1).

Application of the GC–MS–SIM method for rapid determination of pesticide residues in medicinal herb samples used in pharmaceutical and cosmetic industries

Application of the GC–MS–SIM method for rapid determination of pesticide residues in medicinal herb samples used in pharmaceutical and cosmetic industries

Development and Validation of a Combined Methodology for Assessing the Total Quality Control of Herbal Medicinal Products – Application to Oleuropein Preparations

Oleuropein (OE) is a secoiridoid glycoside, which occurs mostly in the Oleaceae family presenting several pharmacological properties, including antioxidant, cardio-protective, anti-atherogenic effects etc. Based on these findings OE is commercially available, as Herbal Medicinal Product (HMP), claimed for its antioxidant effects. As there are general provisions of the medicine regulating bodies e.g. European Medicines Agency, the quality of the HMP’s must always be demonstrated. Therefore, a novel LC-MS methodology was developed and validated for the simultaneous quantification of OE and its main degradation product, hydroxytyrosol (HT), for the relevant OE claimed HMP’s. The internal standard (IS) methodology was employed and separation of OE, HT and IS was achieved on a C18 Fused Core column with 3.1 min overall run time employing the SIM method for the analytical signal acquisition. The method was validated according to the International Conference on Harmonisation requirements and the results show adequate linearity (r2 > 0.99) over a wide concentration range [0.1–15 μg/mL (n=12)] and a LLOQ value of 0.1 μg/mL, for both OE and HT. Furthermore, as it would be beneficial to control the quality taking into account all the substances of the OE claimed HMP’s; a metabolomics-like approach has been developed and applied for the total quality control of the different preparations employing UHPLC-HRMS-multivariate analysis (MVA). Four OE-claimed commercial HMP’s have been randomly selected and MVA similarity-based measurements were performed. The results showed that the examined samples could also be differentiated as evidenced according to their scores plot. Batch to batch reproducibility between the samples of the same brand has also been determined and found to be acceptable. Overall, the developed combined methodology has been found to be an efficient tool for the monitoring of the HMP’s total quality. Only one OE HMP has been found to be consistent to its label claim.

Enzyme-facilitated synthesis of 1-nonene oxide and simple GC-MS SIM method for rapid screening of epoxidation processes

Here, we describe an improved enzyme-facilitated epoxidation of 1-nonene using a conventional water bath shaker at ambient temperature. Enzymes were used to produce peroxy acids instantly from hydrogen peroxide (H2O2) and various perhydrolysis substrates. The peroxy acid generated was then utilised directly for in-situ oxidation of 1-nonene to 1-nonene oxide. Various parameters affecting the reaction were studied such as the nature of the peroxy acids, organic solvents, enzyme sources and enzyme concentrations. The highest conversion rate was achieved using phenylacetic acid as an oxygen carrier. 1-Nonene was converted most efficiently with 95% of the maximum yield by Novozym 435, an immobilised Candida antarctica lipase B, using dichloromethane as the reaction media. A minimum amount (16 mg, 1.4% w/w) of Novozym 435 was needed to maintain catalytic activity (160.0 Ug−1). In addition, a simple and rapid Gas chromatography mass spectroscopy selective ion monitoring (GC-MS SIM) method was developed using a HP-5ms column for determining 1-nonene oxide. The method was found to be linear in the range of 29.9 to 298.8 mg/L with R2 = 0.9981.

Application of robust optimization to automated test assembly

In automated test assembly (ATA), 0-1 linear programming (0-1 LP) methods are applied to select questions (items) from an item bank to assemble an optimal test. The objective in this 0-1 LP optimization problem is to assemble a test that measures, in as precise a way as possible, the ability of candidates. Item response theory (IRT) is commonly applied to model the relationship between the responses of candidates and their ability level. Parameters that describe the characteristics of each item, such as difficulty level and the extent to which an item differentiates between more and less able test takers (discrimination) are estimated in the application of the IRT model. Unfortunately, since all parameters in IRT models have to be estimated, they do have a level of uncertainty to them. Some of the other parameters in the test assembly model, such as average response times, have been estimated with uncertainty as well. General 0-1 LP methods do not take this uncertainty into account, and overestimate the predicted level of measurement precision. In this paper, alternative robust optimization methods are applied. It is demonstrated how the Bertsimas and Sim method can be applied to take this uncertainty into account in ATA. The impact of applying this method is illustrated in two numerical examples. Implications are discussed, and some directions for future research are presented.

Determination of siloxanes in silicone products and potential migration to milk, formula and liquid simulants

A pressurised solvent extraction procedure coupled with a gas chromatography–mass spectrometry–selective ion monitoring (GC–MS–SIM) method was developed to determine three cyclic siloxanes, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and three linear siloxanes, octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), in silicone products. Additionally, two different extraction methods were developed to measure these siloxanes migrating into milk, infant formula and liquid simulants (50 and 95% ethanol in water). The limits of quantification (LOQs) of the six siloxanes ranged from 6 ng/g (L3) to 15 ng/g (D6). Silicone nipples and silicone bakewares were extracted using pressurised solvent extraction (PSE) and analysed using the GC–MS–SIM method. No linear siloxanes were detected in the silicone nipple samples analysed. The three cyclic siloxanes (D4, D5 and D6) were detected in all silicone nipple samples with concentrations ranging from 0.5 to 269 µg/g. In the bakeware samples, except for L3, the other five siloxanes were detected with concentrations ranging from 0.2 µg/g (L4) to 7030 µg/g (D6). To investigate the potential migration of the six siloxanes from silicone nipples to milk and infant formula, a liquid extraction and dispersive clean-up procedure was developed for the two matrices. The procedure used a mix of hexane and ethyl acetate (1 : 1, v/v) as extraction solvent and C18 powder as the dispersive clean-up sorbent. For the liquid simulants, extraction of the siloxanes was achieved using hexane without any salting out or clean-up procedures. The recoveries of the six siloxanes from the milk, infant formula and simulants fortified at 50, 100, 200, 500 and 1000 µg/l ranged from 70 to 120% with a relative standard derivation (RSD) of less than 15% (n = 4). Migration tests were performed by exposing milk, infant formula and the liquid simulants to silicone baking sheets with known concentrations of the six siloxanes at 40°C. No siloxanes were detected in milk or infant formula after 6 h of direct contact with the silicone baking sheet plaques, indicating insignificant migration of the siloxanes to milk or infant formula. Migration tests in the two simulants lasted up to 72 h and the three cyclic siloxanes were detected in 50% ethanol after an 8-h exposure and after 2 h in 95% ethanol. The highest detected concentrations of D4, D5 and D6 were 42, 36 and 155 ng/ml, respectively, indicating very limited migration of D4, D5 or D6 into the two simulants.