Systematic Variation Research Articles

Enrichment and Quantitation of Dipeptidyl Peptidase IV Inhibitory Peptides in Quinoa upon Systematic Malting.

Food-derived peptides with an inhibitory effect on dipeptidyl peptidase IV (DPP-IV) can be used as an additive treatment for type 2 diabetes. The inhibitory potential of food depends on technological protein hydrolysis and gastrointestinal digestion, as the peptides only act after intestinal resorption. The effect of malting as a hydrolytic step on the availability of these peptides in grains has yet to be investigated. In this study, quinoa was malted under systematic temperature, moisture, and time variations. In the resulting malts, the DPP-IV inhibition reached a maximum of 45.02 (±10.28) %, whereas the highest overall concentration of literature-known inhibitory peptides was 4.07 μmol/L, depending on the malting parameters. After in vitro gastrointestinal digest, the inhibition of most malts, as well as the overall concentration of inhibitory peptides, could be increased significantly. Additionally, the digested malts showed higher values in both the inhibition and the peptide concentration than the unmalted quinoa. Concerning the malting parameters, germination time had the highest impact on the inhibition and the peptide concentration after digest. An analysis of the protein sizes before and after malting gave first hints toward the origin of these peptides, or their precursors, in quinoa.

An Observational View of Structure in Protostellar Systems

The envelopes and disks that surround protostars reflect the initial conditions of star and planet formation and govern the assembly of stellar masses. Characterizing these structures requires observations that span the near-IR to centimeter wavelengths. Consequently, the past two decades have seen progress driven by numerous advances in observational facilities across this spectrum, including the Spitzer Space Telescope, Herschel Space Observatory, the Atacama Large Millimeter/submillimeter Array, and a host of other ground-based interferometers and single-dish radio telescopes. ▪ Nearly all protostars have well-formed circumstellar disks that are likely to be rotationally supported; the ability to detect a disk around a protostar is more a question of spatial resolution rather than whether or not a disk is present. ▪ The disks around protostars have inherently higher millimeter/submillimeter luminosities as compared to disks around more-evolved pre-main-sequence stars, though there may be systematic variations between star-forming regions. ▪ The envelopes around protostars are inherently asymmetric, and streamers emphasize that mass flow through the envelopes to the disks may not be homogeneous. ▪ The current mass distribution of protostars may be impacted by selection bias given that it is skewed toward solar-mass protostars, which is inconsistent with the stellar initial mass function.

Modulating Spin Current Induced Effective Damping in β-W/Py Heterostructures by a Systematic Variation in Resistivity of the Sputtered Deposited β-W films

Abstract Utilizing the spin-induced pumping from a ferromagnet (FM) into a heavy metal (HM) under the ferromagnetic resonance (FMR) condition, we report an enhancement in effective damping in β- W/Py bilayers by systematically varying resistivity (ρW) of β-W films. Different resistivity ranging from 100 μΩ-cm to 1400 μΩ-cm with a thickness of 8 nm can be achieved by varying the argon pressure (PAr) during the growth by the method of sputtering. The coefficient of effective damping αeff is observed to increase from 0.010 to 0.025 with ρW, which can be modulated by PAr. We observe a modest dependence of αeff on the sputtering power (pS) while keeping the PAr constant. αeff dependence on both PAr and pS suggests that there exists a strong correlation between αeff and ρW. It is thus possible to utilize ρW as a tuning parameter to regulate the αeff, which can be advantageous for faster magnetization dynamics switching. The thickness dependence study of Py in the aforementioned bilayers manifests a higher spin mixing conductance (g↑↓ eff) which suggests a strong spin pumping from Py into the β-W layer. The effective spin current (JS(eff)) is also evaluated by considering the spin-back flow in this process. Intrinsic spin mixing conductance (g↑↓ W) and spin diffusion length (λSD) of β-W are additionally investigated using thickness variations in β-W. Furthermore, the low-temperature study in β-W/Py reveals an intriguing temperature dependence in αeff, which is quite different from αb of single Py layer and the enhancement in αeff at low temperature can be attributed to the spin-induced pumping from Py layer into β-W.

A comparison of RNA-Seq data preprocessing pipelines for transcriptomic predictions across independent studies

BackgroundRNA sequencing combined with machine learning techniques has provided a modern approach to the molecular classification of cancer. Class predictors, reflecting the disease class, can be constructed for known tissue types using the gene expression measurements extracted from cancer patients. One challenge of current cancer predictors is that they often have suboptimal performance estimates when integrating molecular datasets generated from different labs. Often, the quality of the data is variable, procured differently, and contains unwanted noise hampering the ability of a predictive model to extract useful information. Data preprocessing methods can be applied in attempts to reduce these systematic variations and harmonize the datasets before they are used to build a machine learning model for resolving tissue of origins.ResultsWe aimed to investigate the impact of data preprocessing steps—focusing on normalization, batch effect correction, and data scaling—through trial and comparison. Our goal was to improve the cross-study predictions of tissue of origin for common cancers on large-scale RNA-Seq datasets derived from thousands of patients and over a dozen tumor types. The results showed that the choice of data preprocessing operations affected the performance of the associated classifier models constructed for tissue of origin predictions in cancer.ConclusionBy using TCGA as a training set and applying data preprocessing methods, we demonstrated that batch effect correction improved performance measured by weighted F1-score in resolving tissue of origin against an independent GTEx test dataset. On the other hand, the use of data preprocessing operations worsened classification performance when the independent test dataset was aggregated from separate studies in ICGC and GEO. Therefore, based on our findings with these publicly available large-scale RNA-Seq datasets, the application of data preprocessing techniques to a machine learning pipeline is not always appropriate.

Facile synthesis of acrylamide derivative copolymers with side urethane groups for systematic variation of the thermoresponsive behavior

Facile synthesis of acrylamide derivative copolymers with side urethane groups for systematic variation of the thermoresponsive behavior

Beaconet: A Reference-Free Method for Integrating Multiple Batches of Single-Cell Transcriptomic Data in Original Molecular Space.

Integrating multiple single-cell datasets is essential for the comprehensive understanding of cell heterogeneity. Batch effect is the undesired systematic variations among technologies or experimental laboratories that distort biological signals and hinder the integration of single-cell datasets. However, existing methods typically rely on a selected dataset as a reference, leading to inconsistent integration performance using different references, or embed cells into uninterpretable low-dimensional feature space. To overcome these limitations, a reference-free method, Beaconet, for integrating multiple single-cell transcriptomic datasets in original molecular space by aligning the global distribution of each batch using an adversarial correction network is presented. Through extensive comparisons with 13 state-of-the-art methods, it is demonstrated that Beaconet can effectively remove batch effect while preserving biological variations and is superior to existing unsupervised methods using all possible references in overall performance. Furthermore, Beaconet performs integration in the original molecular feature space, enabling the characterization of cell types and downstream differential expression analysis directly using integrated data with gene-expression features. Additionally, when applying to large-scale atlas data integration, Beaconet shows notable advantages in both time- and space-efficiencies. In summary, Beaconet serves as an effective and efficient batch effect removal tool that can facilitate the integration of single-cell datasets in a reference-free and molecular feature-preserved mode.

Low-density lipoprotein cholesterol response to statins according to comorbidities and co-medications: a population-based study.

The response of low-density lipoprotein cholesterol (LDL-C) to statin therapy is variable, and may be affected by the presence of co-morbid conditions or the use of concomitant medications. Systematic variation in the response to statins based on these factors could affect the selection of the statin treatment regimen in population subgroups. We investigated whether common comorbidities and co-medications had clinically important effects on statin responses in individual patients. This register-based cohort study included 89,006 simvastatin or atorvastatin initiators with measurements of pre-statin and on-statin LDL-C levels, in Denmark, 2008-2018. We defined statin response as the percentage reduction in LDL-C, and used linear regression to estimate percentage reduction differences (PRD) according to 175 chronic comorbidities and 99 co-medications. We evaluated both the statistical significance (p-values corrected for multiple testing) and the clinical importance (PRD of 5 percentage points or more) of the observed associations. Concomitant use of oral blood-glucose lowering drugs, which included metformin in 96% of treated individuals, was associated with a greater response to statin therapy that was both statistically significant and clinically important, with a PRD of 5.18 (95% confidence interval: 4.79 to 5.57). No other comorbidity or co-medication reached the prespecified thresholds for a significant, clinically important effect on statin response. Overall, comorbidities and co-medications had little effect on statin response, and altogether explained only 1.7% of the total observed population variance. Most of the studied comorbidities and co-medications did not have a clinically important effect on statin response, suggesting no need to modify treatment regimens. However, use of metformin was associated with a significantly enhanced LDL-C response to statins, suggesting that lower statin doses may be effective in patients taking metformin.

Age-bias in assessments of medical decision-making capacity: a cross-sectional experimental vignette study

Accurate assessments about medical decision-making capacity (DMC) are vital but could be susceptible to age-bias. We examined if client age impacts on DMC likelihood assessment. One hundred and forty-seven adults were trained to identify four cognitive abilities (i.e., understanding, appreciation, reasoning, expression). Six experimental vignettes described a person making a diabetes treatment decision with systematic variation of client age (unspecified, 50-, or 95-years-old) and abilities (demonstrated vs uncertain). The dependent variable was DMC likelihood. Standardised tests of explicit (Kogan’s Attitudes Toward Old People scale) and implicit age-bias (IAT) were administered. There was a statistically significant effect of abilities on DMC likelihood. DMC was judged more likely when cognitive abilities were demonstrated. There were no other significant effects. Age-bias, measured implicitly and explicitly, did not influence DMC likelihood. Contrary to the hypothesis, DMC likelihood was unaffected by client age. This suggests that training can mitigate age-bias in simulated clinical DMC evaluation.

Palynology of strata associated with the Hercynian unconformity across the Arabian plate, from the Levant to southern Arabia

Abstract A survey of the palynostratigraphy of the strata above and below the Hercynian Unconformity (HU) indicates that the range of its associated hiatus, due to either non-deposition or erosion (or both), varies considerably across the Arabian Plate depending on the position of the succession in relation to the three main highs or arches, the Levant, Al Batin, and Oman-Hadhramaut arches, and any Hercynian faulting or other uplift in basinal regions, for example in the Ghawar region. As expected, the succession spanning the HU is most complete in basinal areas, for example in the Faydah-Jafurah and Nafud-Ma'aniya basins. The well with the shortest hiatus corresponding approximately to a maximum duration of part of the Serpukhovian and Bashkirian, appears to be KH-5/1, close to the axis of the Nafud-Ma'aniya Basin. Palynological assemblages in rocks above the HU indicate the diachronous onset of the basal Khuff clastics northwest through the Arabian Plate over a period of around 15 my. The oldest strata above the HU across the Arabian Plate also indicate systematic variation, probably due to palaeoclimate, with assemblages of similar age in Iraq and northern Saudi Arabia showing some similarities to those of Oman, but differences probably due to a strong climatic gradient at the time.

The recent star formation histories of nearby galaxies on resolved scales

Abstract Star formation histories (SFHs) of galaxies are affected by a variety of factors, both external (field vs. cluster/group) and internal (presence of a bar and AGN, morphological type). In this work, we extend our previous study and apply the $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ metric to a sample of eleven nearby galaxies with MUSE observations. Based on a combination of Hα and UV photometry, $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ is sensitive to star formation timescales of ∼5–200 Myr and therefore measures the present-day rate of change in the star formation rate, dSFR/dt. Within this limited galaxy sample, we do not observe systematic variations between the global value of $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ and the presence of an active galactic nucleus, stellar bar, nor with group or cluster membership. Within some of the individual galaxies, we however observe significant differences in $\langle SFR_{\rm {5}} \rangle \big / \langle SFR_{\rm {200}} \rangle$ between the arm and interarm regions. In half of the galaxies, the recent SFH of both arm and interarm regions has been very similar. However, in the galaxies with higher bulge-to-total light ratios and earlier morphological type, the SFR is declining more rapidly in the interarm regions. This decline in SFR is not a result of low molecular gas surface density or a decrease in the star formation efficiency, implying that other factors are responsible for this SFR decrease.

Three-dimensional Effects on Gap-Resonances in Twin-Hull Vessels in Time-Harmonic Vertical Oscillations

Three-dimensional effects induced by dimensional ratios on the gap resonances happening in twin hull vessels oscillating in forced vertical motion have been analyzed. They can lead to relevant consequences, such as the amplification of the inner radiated waves or the generation of standing waves in between the demi-hulls, that can have a direct effect on the operating profile of the vessel. The response of twin hull vessels in waves can be strongly affected by these resonant phenomena. Also, some of these behaviors can be exploited in the framework of wave energy conversion systems. The present analysis is carried out by using an open-source, linear, Boundary Element Method (BEM), based on the Green function approach. Mathematical backgrounds of the added mass and damping coefficients computation for a floating body under harmonic vertical oscillation are provided as well as details of the numerical discretization used in the BEM. A panel mesh sensitivity study is carried out and the numerical prediction is validated by comparison against available experimental data, another CFD solution obtained by a high-fidelity viscous solver based on the open-source libraries Open-FOAM and approximate analytic formulations. The effect of the beam ratio and the length-to-beam ratio on the resonant phenomena has been analyzed. This has been achieved by systematic variations of the geometric dimensions of the hull, focusing on the trends of the hydrodynamic coefficients, the amplitude of the radiated waves, and the location of the resonant frequencies over the analyzed range.

The frontiers of the Paleo-Tethys Ocean in the western Mediterranean: Isotopic constraints (Sm-Nd) on sources of Devonian units from Menorca Island

The c. 1000-m-thick pre-orogenic Devonian mainly metapelitic sequence of North Menorca Island shows a fairly complete stratigraphic succession. The rocks of this sequence indicate gradually increasing deeper marine conditions of sedimentation towards its uppermost levels. Furthermore, the obtained sedimentary characteristics resemble those related to a deep and narrow basin-associated deposit. Thin sills of Ti-augite-bearing alkaline gabbros occur within the Devonian sequence. The intensity of Variscan deformation increases downwards through the structure. According to the characteristics of the Devonian sequence and its location within the Variscan Orogen, a correlation with similar units located in the southern sectors of the Central Iberian Zone (Iberian Massif) is suggested. The Devonian metapelitic rocks have geochemical characteristics suggesting that they represent moderately recycled mature siliciclastic sediments, generated from erosion of distant source areas belonging to an upper continental crust. The relatively narrow range of variation observed in initial 143Nd/144Nd ratios supports a similar source for the Menorcan slates (0.51165–0.51182). However, a marked trend is observed in these isotope ratios, from lower values at the base of the stratigraphic column (minimum value of 0.511941) to higher values at the top (maximum value of 0.512131). The 147Sm/144Nd ratios vary between 0.1074 and 0.1238, within the range defined for siliciclastic rocks with felsic crustal provenance. The Nd model ages define a narrow range between 1496 Ma and 1754 Ma (Late Paleoproterozoic–Early Mesoproterozoic), and they are consistently younger up-section. These data rule out a provenance from the erosion of the West Africa Craton, as they are more compatible with a provenance from regions located in the Trans-Saharan Belt or Sahara Metacraton. The characteristics of the Menorcan Devonian sequence are compatible with its deposition in a narrow and deep peri-Gondwanan transtensional basin, generated to the south of an advancing Variscan orogenic wedge. Systematic variations in the Nd isotopic composition indicate the progressive and continuous denudation of increasingly more easterly North African sectors in a collisional context between Laurussia and Gondwana with a marked dextral component. These data must be interpreted in the sense that there was not a large oceanic domain during Devonian times to the south of Iberia, able to block the arrival of detrital material from North Africa. A large tract of the Paleo-Tethys Ocean would therefore not have existed during the Devonian south of Iberia. This ocean must therefore have had limited extent in this period towards the westernmost sectors. The Devonian peri-Gondwanan shelf was apparently continuous around Iberia. This platform was progressively affected by Variscan deformation advancing from north to south and incorporated into the Variscan orogenic wedge with the same vergence.

From laboratory to industrial use: Understanding process variation during enzymatic protein hydrolysis with dry film Fourier-Transform Infrared spectroscopy

Industries are continuously looking for dedicated sensor solutions for evaluating the chemical composition of products that can provide valuable insights into process control, process optimization, and product quality. A rapid and robust analytical method, Fourier-Transform Infrared (FTIR) spectroscopy, holds significant potential in this regard as it provides detailed compositional values of food nutrients. The main aim of the present study was to use dry film FTIR spectroscopy as an analytical tool to characterize products from an industrial enzymatic protein hydrolysis process and link this to understand industrial process variations. For this purpose, 463 protein hydrolysate samples were obtained from an industrial enzymatic protein hydrolysis plant. In the same period, systematic variations in process parameters such as raw material composition, enzyme type, and water addition, were performed. All samples were analyzed using dry film FTIR spectroscopy. Two subsets containing 200 and 68 hydrolysate samples were chosen for measuring average molecular weight (AMW) and collagen content respectively, providing reference data for constructing calibration models based on partial least squares regression (PLSR). The percentage of low molecular weight constituents was derived from the molecular weight distribution of size exclusion chromatograms of protein hydrolysates and also used in the modeling. Calibration models for the prediction of AMW, low molecular weight constituents, and collagen content were obtained with a good fit and lower estimation errors. Principal component analysis (PCA) of protein hydrolysates’ FTIR spectra effectively differentiated process variations (enzyme types and raw materials) without extensive reference analysis. One-factor analysis of variance (ANOVA) tests was used to observe the impact of process variation on product quality. FTIR proved to be a sensitive method for liquid protein analysis and process control with a significant potential in process optimization approaches. To the authors’ knowledge, this is the first time dry film FTIR spectroscopy has been used to evaluate an industrial bioprocess with designed process variations.

Investigating the Drivers of Electron Temperature Variations in H ii Regions with Keck-KCWI and VLT-MUSE

H ii region electron temperatures are a critical ingredient in metallicity determinations, and recent observations have revealed systematic variations in the temperatures measured using different ions. We present electron temperatures (T e ) measured using the optical auroral lines ([N ii]λ5756, [O ii]λ λ7320, 7330, [S ii]λ λ4069, 4076, [O iii]λ4363, and [S iii]λ6312) for a sample of H ii regions in seven nearby galaxies. We use observations from the Physics at High Angular resolution in Nearby Galaxies survey (PHANGS) obtained with integral field spectrographs on Keck (Keck Cosmic Web Imager) and the Very Large Telescope (Multi-Unit Spectroscopic Explorer). We compare the different T e measurements with H ii region and ISM environmental properties such as electron density, ionization parameter, molecular gas velocity dispersion, and stellar association/cluster mass and age obtained from PHANGS. We find that the temperatures from [O ii] and [S ii] are likely overestimated due to the presence of electron density inhomogeneities in H ii regions. We measure high [O iii] temperatures in a subset of regions with high molecular gas velocity dispersion and low ionization parameter, which may be explained by the presence of low-velocity shocks. In agreement with previous studies, the T e–T e between [N ii] and [S iii] temperatures have the lowest observed scatter and follow predictions from photoionization modeling, which suggests that these tracers reflect H ii region temperatures across the various ionization zones better than [O ii], [S ii], and [O iii].

Single-shot frequency offset measurement with HASTE using the selective parity approach.

Measurements of frequency offset are commonly required in MRI. The standard method measures the signal phase as a function of evolution time. Here we use a single shot turbo-spin-echo acquisition method to measure frequency offset at a single evolution time. After excitation the transverse magnetisation evolves during the evolution time, and is then repeatedly refocused. The phase is conjugated between alternate echoes. Using partial parallel acquisition techniques we obtain separate odd- and even- echo images. An iterative procedure ensures self-consistency between them. The difference in phase between the two images yields frequency offset maps. The technique was implemented at 3 Tesla and tested on a healthy human volunteer for a range of evolution times between 6 and 42ms. A standard method using a similar readout train and multiple evolution times was used as a gold-standard measure. In a statistical comparison with the gold standard no evidence for bias or offset was found. There was no systematic variation in precision or accuracy as a function of evolution time. We conclude that the presented approach represents a viable method for the rapid generation of frequency offset maps with a high image quality and minimal distortion.

Financial scarcity, psychological well-being and perceptions: an evaluation of the Nigerian currency redesign policy outcomes

BackgroundThe relationship between insufficient financial resources and psychological health has been extensively studied and established in various contexts. However, there remains uncertainty regarding the potential impact of the Nigerian naira currency redesign policy on the psychological well-being of Nigerians. This policy, which aimed to demonetize the economy and promote economic stability, involved changes to the physical appearance of some naira denominations (200, 500 and 1000). Understanding the effects of this policy on psychological health is essential for evaluating its overall societal impact and identifying potential areas for improvement in future currency redesign initiatives.MethodsThe study is a cross-sectional mixed-methods study involving 2237 respondents across the six geopolitical zones of Nigeria. Utilizing the simple random, snowball and convenience sampling technique, social media platforms (Facebook and WhatsApp) were used to recruit respondents. Variables were analyzed at descriptive and inferential levels. The qualitative component comprised seven (7) in-depth interviews with participants across the geo-political zones.ResultsThe perceptions of respondents towards the policy were diverse across different demographic groups. It was widely perceived that the timing of the policy was inappropriate, considering the challenges faced in utilizing online payment platforms and the significant inaccessibility of cash. Furthermore, the analysis revealed that demographic variables played a role in explaining systematic variations in the experience of financial scarcity and its effect on psychological health during the cash crunch that ensued as a result of the Nigerian naira currency redesign policy.ConclusionsThis study identified a significant association between the psychological inventory of financial scarcity and psychological well-being among residents in Nigeria during the cash crunch resulting from the Naira redesign policy. The findings suggest that the financial scarcity experienced by Nigerians due to the policy had a substantial impact on individuals’ psychological well-being. We recommend that a holistic approach be undertaken by policymakers to ensure that policy actions not only address economic objectives but also safeguard the mental health and overall well-being of the population.

Comparative study of surface roughness between electropolishing process and traditional sanding for low carbon steel

Steel is a versatile material utilized across various sectors, encompassing both industrial and decorative applications. AISI (American Iron and Steel Institute) 1005 steel, recognized for its low carbon content (approximately 0.05% carbon), is commonly referred to as mild steel and finds extensive use in society. This study aims to investigate the influence of electropolishing parameters, specifically current density, and time, on the surface roughness of steel. The methodology involved the preparation of samples for electropolishing tests, systematic variation of the parameters, and subsequent analysis of the resulting surface finish through roughness measurements. Samples subjected to higher current densities for shorter durations exhibited substantial reductions in roughness, while longer durations resulted in minimal or negligible changes in roughness regardless of the current density employed. This comparative analysis between electropolishing and tradi-tional sanding techniques provides valuable insights into optimizing surface finishing processes for low carbon steel applications.

Tailoring electrical properties of PVC/PEC/Co3O4 nanocomposites by electron beam irradiation for advanced medium voltage cable applications

This study aimed to investigate the effects of electron beam irradiation on the structural, optical, and electrical properties of polyvinyl chloride/pectin (PVC/PEC) nanocomposites incorporating hexagonal nanoplate Co3O4. Hexagonal nanoplate Co3O4 was synthesized and incorporated into PVC/PEC blends at 5 wt%. The nanocomposites were subjected to electron beam irradiation at varying doses (0, 10, 20, and 30 kGy). Various characterization techniques, including XRD, UV–Vis spectroscopy, AC conductivity, and dielectric measurements, were employed to analyze the irradiated samples. Additionally, electric field distribution simulations were performed for a 33 kV cable model. XRD analysis revealed the retention of Co3O4 crystallinity up to 30 kGy, while the polymer matrix showed degradation above 10 kGy. The optical bandgap decreased from 2.25 eV to 1.90 eV with increasing irradiation dose, indicating changes in the electronic structure. The optimized AC conductivity (37.17 × 10−6 S m−1) and minimum relative permittivity (2.28) were achieved for the 30 kGy irradiated sample with 5 wt% Co3O4. The electric potential distribution gradually decreased from 33,000 V to zero V. The systematic variations in structural, optical, and electrical properties demonstrated controlled tuning of charge transport mechanisms, making these nanocomposites potentially suitable for advanced cable systems. The simulation results showed that the inclusion of Co3O4 at 30 kGy helped maintain a uniform electric field distribution in the 33 kV cable model compared to an unfilled cable.

Difficulty-Generating Features of Text-based Physics Tasks

Influencing the difficulty of performance tasks is of great interest in science education as in several other subjects. In the context of the VAMPS project, difficulty-generating features with respect to the cognitive demand of text-based physics tasks were systematically varied at three levels. Based on preliminary work and two pilot studies presented here briefly, a model was developed by which cognitive requirement was varied according to three features. The viability of this model was empirically tested with a sample of n = 414 secondary school students. The feature <i>cognitive activity</i> proved to be a significant factor influencing the empirically measured difficulty of tasks. With the help of the feature <i>number of information obtained from task stem</i> and <i>number of subject-specific mental procedures</i>, no systematic influence on task difficulty could be shown. The influence of the test persons’ individual prior knowledge on the actual task difficulty is generally assumed to be a confounding factor. Overall, the present study contributes to a better understanding of construct representation in assessments of subject-specific proficiency and empirically confirms that a systematic variation of the task feature <i>cognitive activity</i> on three levels affects task difficulty

Mandrel diameter effect on ring-pull testing of nuclear fuel cladding

Inconsistencies in ring-pull testing methods for thin-walled tubes make it difficult to compare a material's mechanical properties in the hoop direction presented in past publications. The effect of test setup, specifically mandrel diameter, was investigated for nuclear fuel cladding tubes of the iron-chromium-aluminium (FeCrAl) alloy, C26M (Fe-12Cr-6Al-2Mo). Mandrel diameter for ring-pull testing can change how the ring deforms and friction effects, further convoluting the results from testing. To address the impact of mandrel size in relation to ring diameter, gaugeless ring-pull samples were tested across a range of mandrel diameters and compared to uniaxial tensile tests from the same tube of material. Two groups of samples were tested: an as-received, low ductility sample set and an annealed, high ductility sample set, both cut from the same extruded tube. By pairing systematic variation of mandrel geometry with analysis of local strain gradients using digital image correlation, this study investigates the effect of test fixture geometry on apparent mechanical properties and effective strain fields and provides guidance for comparing previously published data. Certain features in uniaxial stress-strain curves (namely the yield strength, ultimate tensile strength, and uniform elongation) appeared to have analogies in the effective stress-strain curves from ring-pull testing. These corresponding features are compared to expose biases in the analysis of material properties using gaugeless ring-pull and to provide novel guidance on test setup during experimental design.