Search results for "direct method"
showing 10 items of 51 documents
Green methodology for quality control of elemental content of infant milk powder
2019
Abstract A green methodology for the direct determination of elemental content in infant milk powder samples from 0 to 3 years was developed. A portable energy dispersive X-ray fluorescence (ED-XRF) tool has been used as a direct method for the quantification of five essential elements (Ca, K, Fe, Cu and Zn). For analysis pellets from 0.8 g of each sample weight were made and analyzed. Due to the high dependence of the ED-XRF signal with the sample matrix, external calibrations using cocoa powder diluted with glucose were performed. Infant milk samples were diluted with lactose and the signals were interpolated in the external calibrations. Concentrations obtained by ED-XRF were compared wi…
Reference interval of monocyte distribution width (MDW) in healthy blood donors.
2020
Abstract Background The aim of the study was to accurately establish the reference interval (RI) of monocyte distribution width (MDW) in healthy blood donors by the direct method using different statistical approaches. Methods MDW was measured in 486 subjects. RI of MDW was calculated by the non-parametric method, the robust method and, the Harrell-Davis bootstrap method and using different tests to identify potential outliers (Dixon-Reed and Tukey). Results Lower and upper reference limits of the RI calculated by the non-parametric method were, 16.22 (90%CI 15.78–16.47) – 23.15 (90%CI 22.80–24.10) (without outlier removal), and 16.44 (90%CI 16.21–16.67) – 22.99 (90%CI 22.33–23.22) (after o…
Learning from learners: a non-standard direct approach to the teaching of writing skills in EFL in a university context
2016
Corpora have been used in English as a foreign language materials for decades, and native corpora have been present in the classroom by means of direct approaches such as Data-Driven Learning (Johns, T., and P. King 1991. 'Should you be Persuaded'- Two Samples of Data-Driven Learning Materials. In Classroom Concordancing,1-16. Birmingham University. English Language Research Journal 4.). However, the suitability of using learners' output in classroom tasks remains controversial. This paper describes a pilot study in the application of a non-standard direct approach where Spanish university students are invited to reflect on their production. In the experiment, carried out in several sessions…
Multivariate standardisation for non-linear calibration range in the chemiluminescence determination of chromium.
2006
Multivariate standardisation is proposed for the successful chemiluminescence determination of chromium based on luminol-hydrogen peroxide reaction. In an extended concentration range, non-linear calibration model is needed. The studied instrumental situations were different detection cells, instruments, assemblies, time and their possible combinations. Chemiluminescence kinetic registers have been transferred using piecewise direct standardisation (PDS) method. The optimisation of transfer parameters has been carried out based on the prediction residual error criteria. Non-linear principal component regression (NL-PCR) and non-linear partial least square regression (NL-PLS) were chosen for…
Reference interval by the indirect approach of serum thyrotropin (TSH) in a Mediterranean adult population and the association with age and gender.
2019
Abstract Background The serum concentration of thyrotropin (TSH) represents a first-line test in diagnostic algorithms. The estimation of TSH reference intervals (RIs) is still a matter of debate due to the high prevalence of subclinical disease making difficult the definition of truly healthy subjects. The aim of this study was to estimate TSH RIs in healthy subjects and to evaluate the effect of age and gender on TSH concentration. Methods Forty-four thousand one hundred and fifty-six TSH data were collected between July 2012 and April 2018 at the Department of Laboratory Medicine, University-Hospital, Palermo. Common and sex-specific RIs were estimated by Arzideh’s indirect method after …
Uzdevumi sākumskolas skolēnu angļu valodas izrunas pilnveidei
2020
Izruna ir nozīmīga angļu valodas apguves daļa. Izrunas prasmes ietekmē spēju radīt skaņas, saprast valodu un uztvert teiktā nozīmi, kas ir būtiski faktori, lai veidotu veiksmīgu komunikāciju. Šī iemesla dēļ sākumskolas angļu valodas stundās vairāk uzmanības būtu jāvelta izrunas uzlabošanas vingrinājumiem. Izvēloties vingrinājumus, nepieciešams ņemt vērā izrunas apguves īpatnības jaunākā skolas vecuma skolēniem. Lai noteiktu metožu un vingrinājumu efektivitāti izrunas prasmju uzlabošanai sākumskolā, tika pielietotas divas mācību metodes, audiolingvālā mācību metode un tiešā metode, Tukuma 2. vidusskolas 4. klases skolēnu angļu valodas stundās. Noslēguma diagnosticējošais tests apstiprināja, …
Nanoscale ear drum: graphene based nanoscale sensors.
2012
The difficulty in determining the mass of a sample increases as its size diminishes. At the nanoscale, there are no direct methods for resolving the mass of single molecules or nanoparticles and so more sophisticated approaches based on electromechanical phenomena are required. More importantly, one demands that such nanoelectromechanical techniques could provide not only information about the mass of the target molecules but also about their geometrical properties. In this sense, we report a theoretical study that illustrates in detail how graphene membranes can operate as nanoelectromechanical mass-sensor devices. Wide graphene sheets were exposed to different types and amounts of molecul…
Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8 from electron diffraction data
2014
The crystal structure of the novel Al77Rh15Ru8phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8E-phase is orthorhombic [Pbma,a= 23.40 (5),b= 16.20 (4) andc= 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E…
Comparison of electron diffraction data from non-linear optically active organic DMABC crystals obtained at 100 and 300 kV
2000
During the recent past, we have synthesized a new class of molecules with intramolecular two-dimensional charge transfer upon excitation. The present report presents such a molecule, 2,6-bis(4-dimethylamino-benzylidene)-cyclohexanone (DMABC), with an unusually high value of the second-order non-linear optical (NLO) coefficients. In order to optimize the macroscopic NLO properties of the compounds, it is necessary to relate their first hyperpolarizability tensors at a molecular level to those at a crystal bulk level. This requires a complete structure determination and refinement. However, the growth of sufficiently large single crystals, which are needed for structural analysis and refineme…
Dynamic reaction cell inductively couple plasma-mass spectrometry optimization for seawater analysis
2018
Abstract A direct method for dynamic reaction cell inductively coupled plasma- mass spectrometry (DRC-ICP-MS) trace mineral elements determination in seawater was optimized by Experimental Statistical Design. Five instrumental parameters, such as radiofrequency, sample, nebulizer and reaction gas flows, rejection parameter q and axial field voltage were studied. A Plackett-Burman design was used for screening the most important parameters and the most significant ones were optimized with a Central composite design. Fifteen elements and different isotopes for some of these were considered through the study. The optimization was achieved by using three different reaction gases (NH3, CH4 and O…