Separating PIAAC competencies from general cognitive skills: A dimensionality and explanatory analysis

This study aims to investigate how test scores from PIAAC (Programme for the International Assessment of Adult Competencies) can be interpreted, by comparing the PIAAC competencies literacy and numeracy to reasoning and perceptual speed. Dimensionality analyses supported, that the PIAAC competencies can be separated into a common factor overlapping with reasoning and perceptual speed, and domain-specific factors. For the common and specific factors, relations to other variables were analyzed. The nested factor for PIAAC literacy was as expected unrelated to age, positively related to learning opportunities during one’s lifetime, and positively related to literacy skill use. The nested factor for PIAAC numeracy was also as expected unrelated to age, against expectation unrelated to learning opportunities during one’s lifetime, and as expected positively related to numeracy skill use. Results support the validity of the intended test score interpretation for PIAAC literacy, while results for PIAAC numeracy were less clear

Evaluating the Robustness of Learning Analytics Results Against Fake Learners

Massive Open Online Courses (MOOCs) collect large amounts of rich data. A primary objective of Learning Analytics (LA) research is studying these data in order to improve the pedagogy of interactive learning environments. Most studies make the underlying assumption that the data represent truthful and honest learning activity. However, previous studies showed that MOOCs can have large cohorts of users that break this assumption and achieve high performance through behaviors such as Cheating Using Multiple Accounts or unauthorized collaboration, and we therefore denote them fake learners. Because of their aberrant behavior, fake learners can bias the results of Learning Analytics (LA) models. The goal of this study is to evaluate the robustness of LA results when the data contain a considerable number of fake learners. Our methodology follows the rationale of ‘replication research’. We challenge the results reported in a well-known, and one of the first LA/PedagogicEfficacy MOOC papers, by replicating its results with and without the fake learners (identified using machine learning algorithms). The results show that fake learners exhibit very different behavior compared to true learners. However, even though they are a significant portion of the student population (∼15%), their effect on the results is not dramatic (does not change trends). We conclude that the LA study that we challenged was robust against fake learners. While these results carry an optimistic message on the trustworthiness of LA research, they rely on data from one MOOC. We believe that this issue should receive more attention within the LA research community, and can explain some ‘surprising’ research results in MOOCs. Keywords: Learning Analytics, Educational Data Mining, MOOCs, Fake Learners, Reliability, IR

Splitting of the pi - rho spectrum in a renormalized light-cone QCD-inspired model

We show that the splitting between the light pseudo-scalar and vector meson states is due to the strong short-range attraction in the ^1S_0 sector which makes the pion and the kaon light particles. We use a light-cone QCD-inspired model of the mass squared operator with harmonic confinement and a Dirac-delta interaction. We apply a renormalization method to define the model, in which the pseudo-scalar ground state mass fixes the renormalized strength of the Dirac-delta interaction.Comment: 9 pages, 2 figures, revtex, accepted by Phys. Rev. D; Corrected typo

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

We report the first experimental evidence for a metallic phase in fluid molecular oxygen. Our electrical conductivity measurements of fluid oxygen under dynamic quasi-isentropic compression show that a non-metal/metal transition occurs at 3.4 fold compression, 4500 K and 1.2 Mbar. We discuss the main features of the electrical conductivity dependence on density and temperature and give an interpretation of the nature of the electrical transport mechanisms in fluid oxygen at these extreme conditions.Comment: RevTeX, 4 figure

Experimental investigation on the controls of clumped isotopologue and hydrogen isotope ratios in microbial methane

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 237 (2018): 339-356, doi:10.1016/j.gca.2018.06.029.The abundance of methane isotopologues with two rare isotopes (e.g., 13CH3D) has been proposed as a tool to estimate the temperature at which methane is formed or thermally equilibrated. It has been shown, however, that microbial methane from surface environments and from laboratory cultures is characterized by low 13CH3D abundance, corresponding to anomalously high apparent 13CH3D equilibrium temperatures. We carried out a series of batch culture experiments to investigate the origin of the non-equilibrium signals in microbial methane by exploring a range of metabolic pathways, growth temperatures, and hydrogen isotope compositions of the media. We found that thermophilic methanogens (Methanocaldococcus jannaschii, Methanothermococcus thermolithotrophicus, and Methanocaldococcus bathoardescens) grown on H2+CO2 at temperatures between 60 and 80°C produced methane with Δ13CH3D values (defined as the deviation from stochastic abundance) of 0.5 to 2.5‰, corresponding to apparent 13CH3D equilibrium temperatures of 200 to 600°C. Mesophilic methanogens (Methanosarcina barkeri and Methanosarcina mazei) grown on H2+CO2, acetate, or methanol produced methane with consistently low Δ13CH3D values, down to -5.2‰. Closed system effects can explain part of the non-equilibrium signals for methane from thermophilic methanogens. Experiments with M. barkeri using D-spiked water or D-labeled acetate (CD3COO-) indicate that 1.6 to 1.9 out of four H atoms in methane originate from water, but Δ13CH3D values of product methane only weakly correlate with the D/H ratio of medium water. Our experimental results demonstrate that low Δ13CH3D values are not specific to the metabolic pathways of methanogenesis, suggesting that they could be produced during enzymatic reactions common in the three methanogenic pathways, such as the reduction of methyl-coenzyme M. Nonetheless C-H bonds inherited from precursor methyl groups may also carry part of non-equilibrium signals.Grants from the National Science Foundation (EAR-1250394 to S.O.), N. Braunsdorf and D. Smit of Shell PTI/EG (to S.O.), the Deep Carbon Observatory (to S.O., M.K., K.-U.H., D.S.G.), the Gottfried Wilhelm Leibniz Program of the Deutsche Forschungsgemeinschaft (HI 616-14-1 to K.- U.H.), and the Heisenberg Program (KO3651-3-1 to M.K.) of the Deutsche Forschungsgemeinschaft supported this study. D.S.G. was also supported by a National Science Foundation Graduate Research Fellowship, the Neil and Anna Rasmussen Foundation Fund, the Grayce B. Kerr Fellowship, and a Shell-MIT Energy Initiative Graduate Fellowship. D.T.W. was supported by a National Defense Science and Engineering Graduate Fellowship. L.C.S. was supported by a NASA Earth and Space Science Fellowship (grant NNX11AP78H)

Observing response processes with eye tracking in international large-scale assessments: evidence from the OECD PIAAC assessment

This paper reports on a pilot study that used eye tracking techniques to make detailed observations of item response processes in the OECD Programme for the International Assessment of Adult Competencies (PIAAC). The lab-based study also recorded physiological responses using measures of pupil diameter and electrodermal activity. The study tested 14 adult respondents as they individually completed the PIAAC computer-based assessment. The eye tracking observations help to fill an ‘explanatory gap’ by providing data on variation in item response processes that are not captured by other sources of process data such as think aloud protocols or computer-generated log files. The data on fixations and saccades provided detailed information on test item response strategies, enabling profiling of respondent engagement and response processes associated with successful performance. Much of that activity does not include the use of the keyboard and mouse, and involves ‘off-screen’ use of pen and paper (and calculator) that are not captured by assessment log-files. In conclusion, this paper points toward an important application of eye tracking in large-scale assessments. This includes insights into response processes in new domains such as adaptive problem-solving that aim to identify individuals’ ability to select and combine resources from the digital and physical environment

‘… a metal conducts and a non-metal doesn't’

In a letter to one of the authors, Sir Nevill Mott, then in his tenth decade, highlighted the fact that the statement ‘… a metal conducts, and a non-metal doesn’t’ can be true only at the absolute zero of temperature, T=0 K. But, of course, experimental studies of metals, non-metals and, indeed, the electronic and thermodynamic transition between these canonical states of matter must always occur above T=0 K, and, in many important cases, for temperatures far above the absolute zero. Here, we review the issues—theoretical and experimental—attendant on studies of the metal to non-metal transition in doped semiconductors at temperatures close to absolute zero (T=0.03 K) and fluid chemical elements at temperatures far above absolute zero (T>1000 K)

Intervention for depression among palliative care patients and their families: A study protocol for evaluation of a training program for professional care staff

Background: Clinical depression is highly prevalent yet under-detected and under-treated in palliative care settings and is associated with a number of adverse medical and psychological outcomes for patients and their family members. This article presents a study protocol to evaluate a training intervention for non-physician palliative care staff to improve the recognition of depression and provide support for depressed patients and their family members. Details of the hypotheses and expected outcomes, study design, training program development and evaluation measures are described.Methods and Design: A randomised controlled trial will be implemented across two palliative care services to evaluate the &ldquo;Training program for professional carers to recognise and manage depression in palliative care settings&rdquo;. Pre-, post- and three-month follow-up data will be collected to assess: the impact of the training on the knowledge, attitudes, self-efficacy and perceived barriers of palliative care staff when working with depression; referral rates for depression; and changes to staff practices. Quantitative and qualitative methods, in the form of self-report questionnaires and interviews with staff and family members, will be used to evaluate the effectiveness of the intervention.Discussion: This study will determine the effectiveness of an intervention that aims to respond to the urgent need for innovative programs to target depression in the palliative care setting. The expected outcome of this study is the validation of an evidence-based training program to improve staff recognition and appropriate referrals for depression, as well as improve psychosocial support for depressed patients and their family members.<br /

A hierarchical latent response model for inferences about examinee engagement in terms of guessing and item‐level non‐response

In low‐stakes assessments, test performance has few or no consequences for examinees themselves, so that examinees may not be fully engaged when answering the items. Instead of engaging in solution behaviour, disengaged examinees might randomly guess or generate no response at all. When ignored, examinee disengagement poses a severe threat to the validity of results obtained from low‐stakes assessments. Statistical modelling approaches in educational measurement have been proposed that account for non‐response or for guessing, but do not consider both types of disengaged behaviour simultaneously. We bring together research on modelling examinee engagement and research on missing values and present a hierarchical latent response model for identifying and modelling the processes associated with examinee disengagement jointly with the processes associated with engaged responses. To that end, we employ a mixture model that identifies disengagement at the item‐by‐examinee level by assuming different data‐generating processes underlying item responses and omissions, respectively, as well as response times associated with engaged and disengaged behaviour. By modelling examinee engagement with a latent response framework, the model allows assessing how examinee engagement relates to ability and speed as well as to identify items that are likely to evoke disengaged test‐taking behaviour. An illustration of the model by means of an application to real data is presented

Deep sequencing of subseafloor eukaryotic rRNA reveals active fungi across marine subsurface provinces

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e56335, doi:10.1371/journal.pone.0056335.The deep marine subsurface is a vast habitat for microbial life where cells may live on geologic timescales. Because DNA in sediments may be preserved on long timescales, ribosomal RNA (rRNA) is suggested to be a proxy for the active fraction of a microbial community in the subsurface. During an investigation of eukaryotic 18S rRNA by amplicon pyrosequencing, unique profiles of Fungi were found across a range of marine subsurface provinces including ridge flanks, continental margins, and abyssal plains. Subseafloor fungal populations exhibit statistically significant correlations with total organic carbon (TOC), nitrate, sulfide, and dissolved inorganic carbon (DIC). These correlations are supported by terminal restriction length polymorphism (TRFLP) analyses of fungal rRNA. Geochemical correlations with fungal pyrosequencing and TRFLP data from this geographically broad sample set suggests environmental selection of active Fungi in the marine subsurface. Within the same dataset, ancient rRNA signatures were recovered from plants and diatoms in marine sediments ranging from 0.03 to 2.7 million years old, suggesting that rRNA from some eukaryotic taxa may be much more stable than previously considered in the marine subsurface.This work was performed with funding from the Center for Dark Energy Biosphere Investigations (C-DEBI) to William Orsi (OCE-0939564) and The Ocean Life Institute (WHOI) to Virginia Edgcomb (OLI-27071359)