Iron homeostasis and its disruption in mouse lung in iron deficiency and overload.

PubMed

Giorgi, Gisela; D'Anna, María Cecilia; Roque, Marta Elena

2015-10-01

What is the central question of this study? The aim was to explore the role and hitherto unclear mechanisms of action of iron proteins in protecting the lung against the harmful effects of iron accumulation and the ability of pulmonary cells to mobilize iron in iron deficiency. What is the main finding and its importance? We show that pulmonary hepcidin appears not to modify cellular iron mobilization in the lung. We propose pathways for supplying iron to the lung in iron deficiency and for protecting the lung against iron excess in iron overload, mediated by the co-ordinated action of iron proteins, such as divalent metal transporter 1, ZRT-IRE-like-protein 14, transferrin receptor, ferritin, haemochromatosis-associated protein and ferroportin. Iron dyshomeostasis is associated with several forms of chronic lung disease, but its mechanisms of action remain to be elucidated. The aim of the present study was to determine the role of the lung in whole-animal models with iron deficiency and iron overload, studying the divalent metal transporter 1 (DMT1), ZRT-IRE-like protein 14 (ZIP14), transferrin receptor (TfR), haemochromatosis-associated protein (HFE), hepcidin, ferritin and ferroportin (FPN) expression. In each model, adult CF1 mice were divided into the following groups (six mice per group): (i) iron-overload model, iron saccharate i.p. and control group (iron adequate), 0.9% NaCl i.p.; and (ii) iron-deficiency model, induced by repeated bleeding, and control group (sham operated). Proteins were assessed by immunohistochemistry and Western blot. In control mice, DMT1 was localized in the cytoplasm of airway cells, and in iron deficiency and overload it was in the apical membrane. Divalent metal transporter 1 and TfR increased in iron deficiency, without changes in iron overload. ZRT-IRE-like protein 14 decreased in airway cells in iron deficiency and increased in iron overload. In iron deficiency, HFE and FPN were immunolocalized close to the apical membrane. Ferroportin increased in iron overload. Prohepcidin was present in control groups, with no changes in iron deficiency and iron overload. In iron overload, ferritin showed intracytoplasmic localization close to the apical membrane of airway cells and intense immunostaining in macrophage-like cells. The results show that pulmonary hepcidin does not appear to modify cellular iron mobilization in the lung. We propose the following two novel pathways in the lung: (i) for supplying iron in iron deficiency, mediated principally by DMT1 and TfR and regulated by the action of FPN and HFE; and (ii) for iron detoxification in order to protect the lung against iron overload, facilitated by the action of DMT1, ZIP14, FPN and ferritin. © 2015 The Authors. Experimental Physiology © 2015 The Physiological Society.

Influence of DNA-methylation on zinc homeostasis in myeloid cells: Regulation of zinc transporters and zinc binding proteins.

PubMed

Kessels, Jana Elena; Wessels, Inga; Haase, Hajo; Rink, Lothar; Uciechowski, Peter

2016-09-01

The distribution of intracellular zinc, predominantly regulated through zinc transporters and zinc binding proteins, is required to support an efficient immune response. Epigenetic mechanisms such as DNA methylation are involved in the expression of these genes. In demethylation experiments using 5-Aza-2'-deoxycytidine (AZA) increased intracellular (after 24 and 48h) and total cellular zinc levels (after 48h) were observed in the myeloid cell line HL-60. To uncover the mechanisms that cause the disturbed zinc homeostasis after DNA demethylation, the expression of human zinc transporters and zinc binding proteins were investigated. Real time PCR analyses of 14 ZIP (solute-linked carrier (SLC) SLC39A; Zrt/IRT-like protein), and 9 ZnT (SLC30A) zinc transporters revealed significantly enhanced mRNA expression of the zinc importer ZIP1 after AZA treatment. Because ZIP1 protein was also enhanced after AZA treatment, ZIP1 up-regulation might be the mediator of enhanced intracellular zinc levels. The mRNA expression of ZIP14 was decreased, whereas zinc exporter ZnT3 mRNA was also significantly increased; which might be a cellular reaction to compensate elevated zinc levels. An enhanced but not significant chromatin accessibility of ZIP1 promoter region I was detected by chromatin accessibility by real-time PCR (CHART) assays after demethylation. Additionally, DNA demethylation resulted in increased mRNA accumulation of zinc binding proteins metallothionein (MT) and S100A8/S100A9 after 48h. MT mRNA was significantly enhanced after 24h of AZA treatment also suggesting a reaction of the cell to restore zinc homeostasis. These data indicate that DNA methylation is an important epigenetic mechanism affecting zinc binding proteins and transporters, and, therefore, regulating zinc homeostasis in myeloid cells. Copyright © 2016 Elsevier GmbH. All rights reserved.

mRNA Regulation of Cardiac Iron Transporters and Ferritin Subunits in a Mouse Model of Iron Overload

PubMed Central

Brewer, Casey J.; Wood, Ruth I.; Wood, John C.

2014-01-01

Iron cardiomyopathy is the leading cause of death in iron overload. Men have twice the mortality rate of women, though the cause is unknown. In hemojuvelin-knockout mice, a model of the disease, males load more cardiac iron than females. We postulated that sex differences in cardiac iron import cause differences in cardiac iron concentration. RT-PCR was used to measure mRNA of cardiac iron transporters in hemojuvelin-knockout mice. No sex differences were discovered among putative importers of non-transferrin bound iron (L-type and T-type calcium channels, ZRT/IRT-like protein 14 zinc channels). Transferrin-bound iron transporters were also analyzed; these are controlled by the iron regulatory element/iron regulatory protein (IRE/IRP) system. There was a positive relationship between cardiac iron and ferroportin mRNA in both sexes, but it was significantly steeper in females (p<0.05). Transferrin receptor 1 and divalent metal transporter 1 were more highly expressed in females than males (p<0.01 and p<0.0001, respectively), consistent with their lower cardiac iron levels, as predicted by IRE/IRP regulatory pathways. Light-chain (L) ferritin showed a positive correlation with cardiac iron that was nearly identical in males and females (R2=0.41, p<0.01 and R2=0.56, p<0.05, respectively), while heavy-chain (H) ferritin was constitutively expressed in both sexes. This represents the first report of IRE/IRP regulatory pathways in the heart. Transcriptional regulation of ferroportin was suggested in both sexes, creating a potential mechanism for differential set points for iron export. Constitutive H-ferritin expression suggests a logical limit to cardiac iron buffering capacity at levels known to produce heart failure in humans. PMID:25220979

Zinc deficiency mediates alcohol-induced apoptotic cell death in the liver of rats through activating ER and mitochondrial cell death pathways

PubMed Central

Sun, Qian; Zhong, Wei; Zhang, Wenliang; Li, Qiong; Sun, Xiuhua; Tan, Xiaobing; Sun, Xinguo; Dong, Daoyin

2015-01-01

Hepatic zinc deficiency has been well documented in alcoholic patients, but the mechanisms by which zinc deficiency mediates cell death have not been well defined. The objectives of this study were to determine whether alcohol perturbs subcellular zinc homeostasis and how organelle zinc depletion may link with cell death pathways. Wistar rats were pair-fed with the Lieber-DeCarli control or ethanol diet for 5 mo. Chronic alcohol exposure significantly reduced zinc level in isolated hepatic endoplasmic reticulum (ER) and mitochondria. Among the detected zinc transporters, ER Zrt/Irt-like protein (ZIP)13 and mitochondrial ZIP8, which transport zinc from ER and mitochondria to cytosol, were significantly increased. Mitochondrial zinc transporter (ZnT) 4, which transports zinc from cytosol to mitochondria, was also increased. ER phosphorylated eukaryotic initiation factor 2α, activating transcription factor 4, and C/EBP homologous protein were significantly upregulated, and mitochondrial cytochrome c release and Bax insertion were detected in association with caspase-3 activation and apoptotic cell death. To define the role of zinc deficiency in ER and mitochondrial stress, H4IIEC3 cells were treated with 3 μM N,N,N′,N′-tetrakis (2-pyridylmethyl) ethylenediamine for 6 h with or without supplementation with zinc or N-acetylcysteine (NAC). The results demonstrated that zinc deprivation induced caspase-3 activation and apoptosis in association with ER and mitochondria dysfunction, which were inhibited by zinc as low as 10 μM but not by 2 mM NAC. These results suggest that chronic ethanol exposure induced in ER and mitochondrial zinc deficiency might activate intrinsic cell death signaling pathway, which could not be effectively rescued by antioxidant treatment. PMID:25767260

Comparison of cytotoxicity and expression of metal regulatory genes in zebrafish (Danio rerio) liver cells exposed to cadmium sulfate, zinc sulfate and quantum dots.

PubMed

Tang, Song; Allagadda, Vinay; Chibli, Hicham; Nadeau, Jay L; Mayer, Gregory D

2013-10-01

Recent advances in the ability to manufacture and manipulate materials at the nanometer scale have led to increased production and use of many types of nanoparticles. Quantum dots (QDs) are small, fluorescent nanoparticles composed of a core of semiconductor material (e.g. cadmium selenide, zinc sulfide) and shells or dopants of other elements. Particle core composition, size, shell, and surface chemistry have all been found to influence toxicity in cells. The aim of this study was to compare the toxicities of ionic cadmium (Cd) and zinc (Zn) and Cd- and Zn-containing QDs in zebrafish liver cells (ZFL). As expected, Cd(2+) was more toxic than Zn(2+), and the general trend of IC50-24 h values of QDs was determined to be CdTe < CdSe/ZnS or InP/ZnS, suggesting that ZnS-shelled CdSe/ZnS QDs were more cytocompatible than bare core CdTe crystals. Smaller QDs showed greater toxicity than larger QDs. Isolated mRNA from these exposures was used to measure the expression of metal response genes including metallothionein (MT), metal response element-binding transcription factor (MTF-1), divalent metal transporter (DMT-1), zrt and irt like protein (ZIP-1) and the zinc transporter, ZnT-1. CdTe exposure induced expression of these genes in a dose dependent manner similar to that of CdSO4 exposure. However, CdSe/ZnS and InP/ZnS altered gene expression of metal homeostasis genes in a manner different from that of the corresponding Cd or Zn salts. This implies that ZnS shells reduce QD toxicity attributed to the release of Cd(2+), but do not eliminate toxic effects caused by the nanoparticles themselves.

An uncleaved signal peptide directs the Malus xiaojinensis iron transporter protein Mx IRT1 into the ER for the PM secretory pathway.

PubMed

Zhang, Peng; Tan, Song; Berry, James O; Li, Peng; Ren, Na; Li, Shuang; Yang, Guang; Wang, Wei-Bing; Qi, Xiao-Ting; Yin, Li-Ping

2014-11-07

Malus xiaojinensis iron-regulated transporter 1 (Mx IRT1) is a highly effective inducible iron transporter in the iron efficient plant Malus xiaojinensis. As a multi-pass integral plasma membrane (PM) protein, Mx IRT1 is predicted to consist of eight transmembrane domains, with a putative N-terminal signal peptide (SP) of 1-29 amino acids. To explore the role of the putative SP, constructs expressing Mx IRT1 (with an intact SP) and Mx DsIRT1 (with a deleted SP) were prepared for expression in Arabidopsis and in yeast. Mx IRT1 could rescue the iron-deficiency phenotype of an Arabidopsis irt1 mutant, and complement the iron-limited growth defect of the yeast mutant DEY 1453 (fet3fet4). Furthermore, fluorescence analysis indicated that a chimeric Mx IRT1-eGFP (enhanced Green Fluorescent Protein) construct was translocated into the ER (Endoplasmic reticulum) for the PM sorting pathway. In contrast, the SP-deleted Mx DsIRT1 could not rescue either of the mutant phenotypes, nor direct transport of the GFP signal into the ER. Interestingly, immunoblot analysis indicated that the SP was not cleaved from the mature protein following transport into the ER. Taken together, data presented here provides strong evidence that an uncleaved SP determines ER-targeting of Mx IRT1 during the initial sorting stage, thereby enabling the subsequent transport and integration of this protein into the PM for its crucial role in iron uptake.

Expression of Malus xiaojinensis IRT1 (MxIRT1) protein in transgenic yeast cells leads to degradation through autophagy in the presence of excessive iron.

PubMed

Li, Shuang; Zhang, Xi; Zhang, Xiu-Yue; Xiao, Wei; Berry, James O; Li, Peng; Jin, Si; Tan, Song; Zhang, Peng; Zhao, Wei-Zhong; Yin, Li-Ping

2015-07-01

Iron is essential for plants, but highly toxic when present in excess. Consequently, iron uptake by root transporters must be finely tuned to avoid excess uptake from soil under iron excess. The iron-regulated transporter of Malus xiaojinensis (MxIRT1), induced in roots under iron deficiency, is a highly effective iron(II) transporter. Here, we investigated how the presence of excessive iron leads to MxIRT1 degradation in yeast expressing this plant iron transporter protein. To determine the relationship between iron abundance and MxIRT1 degradation, relative levels of autophagy-related gene-8 (ATG8) mRNA and the active ATG8-phosphatidylethanolamine-conjugated (PE) protein were measured in wild-type yeast and the autophagic mutant strains atg1∆, atg5∆, atg7∆, ypt7∆ and tor1∆ under normal and excessive iron conditions. The data showed that the exposure of MxIRT1-eGFP-transformed wild-type and tor1∆ strains to excessive iron led to significantly increased levels of ATG8 transcript and ATG8-PE protein, which resulted in enhanced MxIRT1 degradation. Co-localization of mCherry-ATG8 and MxIRT1-eGFP provided evidence that these proteins interact during autophagy in yeast. While inhibition of autophagic initiation, autophagosome formation and vacuole fusion all decreased MxIRT1 degradation. PMSF inhibition of autophagy prevented degradation, leading to the accumulation of MxIRT1-containing vesicles in the vacuoles. MxIRT1-vesicles were sorted into autophagosomes for iron-induced degradation in yeast, whereas the endogenous iron(II) transporter Fet4 was degraded in an autophagy-independent manner. Moreover, immunoprecipitation showed that multimono-ubiquitins provided MxIRT1 with the ubiquitination signal. Together, three factors, iron excess, autophagy and mono-ubiquitination, affect the functional activity and stability of exogenous MxIRT1 in yeast, thereby preventing iron uptake via this root transporter. Copyright © 2015 John Wiley & Sons, Ltd.

mRNA Levels of Placental Iron and Zinc Transporter Genes Are Upregulated in Gambian Women with Low Iron and Zinc Status.

PubMed

Jobarteh, Modou Lamin; McArdle, Harry J; Holtrop, Grietje; Sise, Ebrima A; Prentice, Andrew M; Moore, Sophie E

2017-07-01

Background: The role of the placenta in regulating micronutrient transport in response to maternal status is poorly understood. Objective: We investigated the effect of prenatal nutritional supplementation on the regulation of placental iron and zinc transport. Methods: In a randomized trial in rural Gambia [ENID (Early Nutrition and Immune Development)], pregnant women were allocated to 1 of 4 nutritional intervention arms: 1 ) iron and folic acid (FeFol) tablets (FeFol group); 2 ) multiple micronutrient (MMN) tablets (MMN group); 3 ) protein energy (PE) as a lipid-based nutrient supplement (LNS; PE group); and 4 ) PE and MMN (PE+MMN group) as LNS. All arms included iron (60 mg/d) and folic acid (400 μg/d). The MMN and PE+MMN arms included 30 mg supplemental Zn/d. In a subgroup of ∼300 mother-infant pairs, we measured maternal iron status, mRNA levels of genes encoding for placental iron and zinc transport proteins, and cord blood iron levels. Results: Maternal plasma iron concentration in late pregnancy was 45% and 78% lower in the PE and PE+MMN groups compared to the FeFol and MMN groups, respectively ( P < 0.001). The mRNA levels of the placental iron uptake protein transferrin receptor 1 were 30-49% higher in the PE and PE+MMN arms than in the FeFol arm ( P < 0.031), and also higher in the PE+MMN arm (29%; P = 0.042) than in the MMN arm. Ferritin in infant cord blood was 18-22% lower in the LNS groups ( P < 0.024). Zinc supplementation in the MMN arm was associated with higher maternal plasma zinc concentrations (10% increase; P < 0.001) than in other intervention arms. mRNA levels for intracellular zinc-uptake proteins, in this case zrt, irt-like protein (ZIP) 4 and ZIP8, were 96-205% lower in the PE+MMN arm than in the intervention arms without added zinc ( P < 0.025). Furthermore, mRNA expression of ZIP1 was 85% lower in the PE+MMN group than in the PE group ( P = 0.003). Conclusion: In conditions of low maternal iron and in the absence of supplemental zinc, the placenta upregulates the gene expression of iron and zinc uptake proteins, presumably in order to meet fetal demands in the face of low maternal supply. The ENID trial was registered at www.controlled-trials.com as ISRCTN49285450.

Mucolytic Agents Can Enhance HER2 Receptor Accessibility for [(89)Zr]Trastuzumab, Improving HER2 Imaging in a Mucin-Overexpressing Breast Cancer Xenograft Mouse Model.

PubMed

Wimana, Zéna; Gebhart, G; Guiot, T; Vanderlinden, B; Morandini, R; Doumont, G; Sherer, F; Van Simaeys, G; Goldman, S; Ghanem, G; Flamen, P

2015-10-01

Binding of trastuzumab to HER2 receptors can be impaired by steric hindrance caused by mucin MUC4. As mucolytic drugs can breakdown disulfide bonds of mucoproteins, we checked if this approach could positively affect zirconium-89-labeled trastuzumab ([(89)Zr]T) binding/uptake. The effect of N-acetylcysteine (NAC) and MUC4 knockdown/stimulation on [(89)Zr]T binding/uptake were evaluated in MCF7(HER2-), BT474 and SKBr3(HER2+/MUC4-), and JIMT1(HER2+/MUC4+) cell lines. The results were then validated in SKBR3 and JIMT1 tumor-bearing nude mice with a microPET-CT and ex vivo analysis. Significant increases in [(89)Zr]T binding/uptake were observed in JIMT1 cells following MUC4 knockdown (62.4 ± 6.5%) and exposure to NAC (62.8 ± 19.4%). Compared to controls, mice treated with NAC showed a significant increase in [(89)Zr]T uptake in MUC4 tumors on microPET-CT (SUVmean (18.3 ± 4.7%), SUVmax (41.7 ± 8.4%)) and individual organ counting (37.3 ± 18.3%). In contrast, no significant differences were observed in SKBr3. NAC can enhance [(89)Zr]T accumulation and improve the HER2 imaging of MUC4-overexpressing tumors. The potential positive impact on trastuzumab-based treatment deserves further investigation.

Polarization of IRON-REGULATED TRANSPORTER 1 (IRT1) to the plant-soil interface plays crucial role in metal homeostasis.

PubMed

Barberon, Marie; Dubeaux, Guillaume; Kolb, Cornelia; Isono, Erika; Zelazny, Enric; Vert, Grégory

2014-06-03

In plants, the controlled absorption of soil nutrients by root epidermal cells is critical for growth and development. IRON-REGULATED TRANSPORTER 1 (IRT1) is the main root transporter taking up iron from the soil and is also the main entry route in plants for potentially toxic metals such as manganese, zinc, cobalt, and cadmium. Previous work demonstrated that the IRT1 protein localizes to early endosomes/trans-Golgi network (EE/TGN) and is constitutively endocytosed through a monoubiquitin- and clathrin-dependent mechanism. Here, we show that the availability of secondary non-iron metal substrates of IRT1 (Zn, Mn, and Co) controls the localization of IRT1 between the outer polar domain of the plasma membrane and EE/TGN in root epidermal cells. We also identify FYVE1, a phosphatidylinositol-3-phosphate-binding protein recruited to late endosomes, as an important regulator of IRT1-dependent metal transport and metal homeostasis in plants. FYVE1 controls IRT1 recycling to the plasma membrane and impacts the polar delivery of this transporter to the outer plasma membrane domain. This work establishes a functional link between the dynamics and the lateral polarity of IRT1 and the transport of its substrates, and identifies a molecular mechanism driving polar localization of a cell surface protein in plants.

The probiotic mixture IRT5 ameliorates age-dependent colitis in rats.

PubMed

Jeong, Jin-Ju; Woo, Jae-Yeon; Ahn, Young-Tae; Shim, Jae-Hun; Huh, Chul-Sung; Im, Sin-Heog; Han, Myung Joo; Kim, Dong-Hyun

2015-06-01

To investigate the anti-inflammatory effect of probiotics, we orally administered IRT5 (1×10(9)CFU/rat) for 8 weeks to aged (16 months-old) Fischer 344 rats, and measured parameters of colitis. The expression levels of the inflammatory markers' inducible NO synthase (iNOS), cyclooxygenase-2 (COX2), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β were higher in the colons of normal aged rats (18 months-old) than in the colons of normal young rats (6 months-old). Treatment with IRT5 suppressed the age-associated increased expression of iNOS, COX2, TNF-α, and IL-1β, and activation of NF-κB and mitogen-activated protein kinases. In a similar manner, the expression of tight junction proteins in the colon of normal aged rats was suppressed more potently than in normal young rats, and treatment of aged rats with IRT5 decreased the age-dependent suppression of tight junction proteins ZO-1, occludin, and claudin-1. Treatment with IRT5 suppressed age-associated increases in expressions of senescence markers p16 and p53 in the colon of aged rats, but increased age-suppressed expression of SIRT1. However, treatment with IRT5 inhibited age-associated increased myeloperoxidase activity in the colon. In addition, treatment with IRT5 lowered the levels of LPS in intestinal fluid and blood of aged rats, as well as the reduced concentrations of reactive oxygen species, malondialdehyde, and C-reactive protein in the blood. These findings suggest that IRT5 treatment may suppress age-dependent colitis by inhibiting gut microbiota LPS production. Copyright © 2015 Elsevier B.V. All rights reserved.

The ZIP family zinc transporters support the virulence of Cryptococcus neoformans

PubMed Central

Do, Eunsoo; Hu, Guanggan; Caza, Mélissa; Kronstad, James W.; Jung, Won Hee

2016-01-01

Zinc is an essential element in living organisms and a cofactor for various metalloproteins. To disseminate and survive, a pathogenic microbe must obtain zinc from the host, which is an environment with extremely limited zinc availability. In this study, we investigated the roles of the ZIP family zinc transporters Zip1 and Zip2 in the human pathogenic fungus Cryptococcus neoformans. Zip1 and Zip2 are homologous to Zrt1 and Zrt2 of the model fungus, Saccharomyces cerevisiae, respectively. We found that the expression of ZIP1 was regulated by the zinc concentration in the environment. Furthermore, the mutant lacking ZIP1 displayed a severe growth defect under zinc-limited conditions, while the mutant lacking ZIP2 displayed normal growth. Inductively coupled plasma–atomic emission spectroscopy analysis showed that the absence of Zip1 expression significantly reduced total cellular zinc levels relative to that in the wild type, while overexpression of Zip1 was associated with increased cellular zinc levels. These findings suggested that Zip1 plays roles in zinc uptake in C. neoformans. We also constructed a Zip1-FLAG fusion protein and found, by immunofluorescence, not only that the protein was localized to the periphery implying it is a membrane transporter, but also that the protein was N-glycosylated. Furthermore, the mutant lacking ZIP1 showed attenuated virulence in a murine inhalation model of cryptococcosis and reduced survival within murine macrophages. Overall, our data suggest that Zip1 plays essential roles in zinc transport and the virulence of C. neoformans. PMID:27118799

Splicing factor SR34b mutation reduces cadmium tolerance in Arabidopsis by regulating iron-regulated transporter 1 gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wentao; Du, Bojing; Liu, Di

Highlights: • Arabidopsis splicing factor SR34b gene is cadmium-inducible. • SR34b T-DNA insertion mutant is sensitive to cadmium due to high cadmium uptake. • SR34b is a regulator of cadmium transporter IRT1 at the posttranscription level. • These results highlight the roles of splicing factors in cadmium tolerance of plant. - Abstract: Serine/arginine-rich (SR) proteins are important splicing factors. However, the biological functions of plant SR proteins remain unclear especially in abiotic stresses. Cadmium (Cd) is a non-essential element that negatively affects plant growth and development. In this study, we provided clear evidence for SR gene involved in Cd tolerancemore » in planta. Systemic expression analysis of 17 Arabidopsis SR genes revealed that SR34b is the only SR gene upregulated by Cd, suggesting its potential roles in Arabidopsis Cd tolerance. Consistent with this, a SR34b T-DNA insertion mutant (sr34b) was moderately sensitive to Cd, which had higher Cd{sup 2+} uptake rate and accumulated Cd in greater amounts than wild-type. This was due to the altered expression of iron-regulated transporter 1 (IRT1) gene in sr34b mutant. Under normal growth conditions, IRT1 mRNAs highly accumulated in sr34b mutant, which was a result of increased stability of IRT1 mRNA. Under Cd stress, however, sr34b mutant plants had a splicing defect in IRT1 gene, thus reducing the IRT1 mRNA accumulation. Despite of this, sr34b mutant plants still constitutively expressed IRT1 proteins under Cd stress, thereby resulting in Cd stress-sensitive phenotype. We therefore propose the essential roles of SR34b in posttranscriptional regulation of IRT1 expression and identify it as a regulator of Arabidopsis Cd tolerance.« less

The Components of the Unique Zur Regulon of Cupriavidus metallidurans Mediate Cytoplasmic Zinc Handling

PubMed Central

Bütof, Lucy; Schmidt-Vogler, Christopher; Herzberg, Martin; Große, Cornelia

2017-01-01

ABSTRACT Zinc is an essential trace element, yet it is toxic at high concentrations. In the betaproteobacterium Cupriavidus metallidurans, the highly efficient removal of surplus zinc from the periplasm is responsible for the outstanding metal resistance of the organism. Rather than having a typical Zur-dependent, high-affinity ATP-binding cassette transporter of the ABC protein superfamily for zinc uptake at low concentrations, C. metallidurans has the secondary zinc importer ZupT of the zinc-regulated transporter, iron-regulated transporter (ZRT/IRT)-like protein (ZIP) family. It is important to understand, therefore, how this zinc-resistant bacterium copes with exposure to low zinc concentrations. Members of the Zur regulon in C. metallidurans were identified by comparing the transcriptomes of a Δzur mutant and its parent strain. The consensus sequence of the Zur-binding box was derived for the zupTp promoter-regulatory region by use of a truncation assay. The motif was used to predict possible Zur boxes upstream of Zur regulon members. The binding of Zur to these boxes was confirmed. Two Zur boxes upstream of the cobW1 gene, encoding a putative zinc chaperone, proved to be required for complete repression of cobW1 and its downstream genes in cells cultivated in mineral salts medium. A Zur box upstream of each of zur-cobW2, cobW3, and zupT permitted both low expression levels of these genes and their upregulation under conditions of zinc starvation. This demonstrates a compartmentalization of zinc homeostasis in C. metallidurans, where the periplasm is responsible for the removal of surplus zinc, cytoplasmic components are responsible for the management of zinc as an essential cofactor, and the two compartments are connected by ZupT. IMPORTANCE Elucidating zinc homeostasis is necessary for understanding both host-pathogen interactions and the performance of free-living bacteria in their natural environments. Escherichia coli acquires zinc under conditions of low zinc concentrations via the Zur-controlled ZnuABC importer of the ABC superfamily, and this was also the paradigm for other bacteria. In contrast, the heavy-metal-resistant bacterium C. metallidurans achieves high tolerance to zinc through sophisticated zinc handling and efflux systems operating on periplasmic zinc ions, so that removal of surplus zinc is a periplasmic feature in this bacterium. It is shown here that this process is augmented by the management of zinc by cytoplasmic zinc chaperones, whose synthesis is controlled by the Zur regulator. This demonstrates a new mechanism, involving compartmentalization, for organizing zinc homeostasis. PMID:28808127

Two iron-regulated transporter (IRT) genes showed differential expression in poplar trees under iron or zinc deficiency.

PubMed

Huang, Danqiong; Dai, Wenhao

2015-08-15

Two iron-regulated transporter (IRT) genes were cloned from the iron chlorosis resistant (PtG) and susceptible (PtY) Populus tremula 'Erecta' lines. Nucleotide sequence analysis showed no significant difference between PtG and PtY. The predicted proteins contain a conserved ZIP domain with 8 transmembrane (TM) regions. A ZIP signature sequence was found in the fourth TM domain. Phylogenetic analysis revealed that PtIRT1 was clustered with tomato and tobacco IRT genes that are highly responsible to iron deficiency. The PtIRT3 gene was clustered with the AtIRT3 gene that was related to zinc and iron transport in plants. Tissue specific expression indicated that PtIRT1 only expressed in the root, while PtIRT3 constitutively expressed in all tested tissues. Under iron deficiency, the expression of PtIRT1 was dramatically increased and a significantly higher transcript level was detected in PtG than in PtY. Iron deficiency also enhanced the expression of PtIRT3 in PtG. On the other hand, zinc deficiency down-regulated the expression of PtIRT1 and PtIRT3 in both PtG and PtY. Zinc accumulated significantly under iron-deficient conditions, whereas the zinc deficiency showed no significant effect on iron accumulation. A yeast complementation test revealed that the PtIRT1 and PtIRT3 genes could restore the iron uptake ability under the iron uptake-deficiency condition. The results will help understand the mechanisms of iron deficiency response in poplar trees and other woody species. Copyright © 2015 Elsevier GmbH. All rights reserved.

Using iRT, a normalized retention time for more targeted measurement of peptides

PubMed Central

Escher, Claudia; Reiter, Lukas; MacLean, Brendan; Ossola, Reto; Herzog, Franz; Chilton, John; MacCoss, Michael J.; Rinner, Oliver

2014-01-01

Multiple reaction monitoring (MRM) has recently become the method of choice for targeted quantitative measurement of proteins using mass spectrometry. The method, however, is limited in the number of peptides that can be measured in one run. This number can be markedly increased by scheduling the acquisition if the accurate retention time (RT) of each peptide is known. Here we present iRT, an empirically derived dimensionless peptide-specific value that allows for highly accurate RT prediction. The iRT of a peptide is a fixed number relative to a standard set of reference iRT-peptides that can be transferred across laboratories and chromatographic systems. We show that iRT facilitates the setup of multiplexed experiments with acquisition windows more than 4 times smaller compared to in silico RT predictions resulting in improved quantification accuracy. iRTs can be determined by any laboratory and shared transparently. The iRT concept has been implemented in Skyline, the most widely used software for MRM experiments. PMID:22577012

Using iRT, a normalized retention time for more targeted measurement of peptides.

PubMed

Escher, Claudia; Reiter, Lukas; MacLean, Brendan; Ossola, Reto; Herzog, Franz; Chilton, John; MacCoss, Michael J; Rinner, Oliver

2012-04-01

Multiple reaction monitoring (MRM) has recently become the method of choice for targeted quantitative measurement of proteins using mass spectrometry. The method, however, is limited in the number of peptides that can be measured in one run. This number can be markedly increased by scheduling the acquisition if the accurate retention time (RT) of each peptide is known. Here we present iRT, an empirically derived dimensionless peptide-specific value that allows for highly accurate RT prediction. The iRT of a peptide is a fixed number relative to a standard set of reference iRT-peptides that can be transferred across laboratories and chromatographic systems. We show that iRT facilitates the setup of multiplexed experiments with acquisition windows more than four times smaller compared to in silico RT predictions resulting in improved quantification accuracy. iRTs can be determined by any laboratory and shared transparently. The iRT concept has been implemented in Skyline, the most widely used software for MRM experiments. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NOD promoter-controlled AtIRT1 expression functions synergistically with NAS and FERRITIN genes to increase iron in rice grains.

PubMed

Boonyaves, Kulaporn; Gruissem, Wilhelm; Bhullar, Navreet K

2016-02-01

Rice is a staple food for over half of the world's population, but it contains only low amounts of bioavailable micronutrients for human nutrition. Consequently, micronutrient deficiency is a widespread health problem among people who depend primarily on rice as their staple food. Iron deficiency anemia is one of the most serious forms of malnutrition. Biofortification of rice grains for increased iron content is an effective strategy to reduce iron deficiency. Unlike other grass species, rice takes up iron as Fe(II) via the IRON REGULATED TRANSPORTER (IRT) in addition to Fe(III)-phytosiderophore chelates. We expressed Arabidopsis IRT1 (AtIRT1) under control of the Medicago sativa EARLY NODULIN 12B promoter in our previously developed high-iron NFP rice lines expressing NICOTIANAMINE SYNTHASE (AtNAS1) and FERRITIN. Transgenic rice lines expressing AtIRT1 alone had significant increases in iron and combined with NAS and FERRITIN increased iron to 9.6 µg/g DW in the polished grains that is 2.2-fold higher as compared to NFP lines. The grains of AtIRT1 lines also accumulated more copper and zinc but not manganese. Our results demonstrate that the concerted expression of AtIRT1, AtNAS1 and PvFERRITIN synergistically increases iron in both polished and unpolished rice grains. AtIRT1 is therefore a valuable transporter for iron biofortification programs when used in combination with other genes encoding iron transporters and/or storage proteins.

Applying item response theory and computer adaptive testing: the challenges for health outcomes assessment.

PubMed

Fayers, Peter M

2007-01-01

We review the papers presented at the NCI/DIA conference, to identify areas of controversy and uncertainty, and to highlight those aspects of item response theory (IRT) and computer adaptive testing (CAT) that require theoretical or empirical research in order to justify their application to patient reported outcomes (PROs). IRT and CAT offer exciting potential for the development of a new generation of PRO instruments. However, most of the research into these techniques has been in non-healthcare settings, notably in education. Educational tests are very different from PRO instruments, and consequently problematic issues arise when adapting IRT and CAT to healthcare research. Clinical scales differ appreciably from educational tests, and symptoms have characteristics distinctly different from examination questions. This affects the transferring of IRT technology. Particular areas of concern when applying IRT to PROs include inadequate software, difficulties in selecting models and communicating results, insufficient testing of local independence and other assumptions, and a need of guidelines for estimating sample size requirements. Similar concerns apply to differential item functioning (DIF), which is an important application of IRT. Multidimensional IRT is likely to be advantageous only for closely related PRO dimensions. Although IRT and CAT provide appreciable potential benefits, there is a need for circumspection. Not all PRO scales are necessarily appropriate targets for this methodology. Traditional psychometric methods, and especially qualitative methods, continue to have an important role alongside IRT. Research should be funded to address the specific concerns that have been identified.

Newborn screening for cystic fibrosis in Wisconsin: comparison of biochemical and molecular methods.

PubMed

Gregg, R G; Simantel, A; Farrell, P M; Koscik, R; Kosorok, M R; Laxova, A; Laessig, R; Hoffman, G; Hassemer, D; Mischler, E H; Splaingard, M

1997-06-01

To evaluate neonatal screening for cystic fibrosis (CF), including study of the screening procedures and characteristics of false-positive infants, over the past 10 years in Wisconsin. An important objective evolving from the original design has been to compare use of a single-tier immunoreactive trypsinogen (IRT) screening method with that of a two-tier method using IRT and analyses of samples for the most common cystic fibrosis transmembrane regulator (CFTR) (DeltaF508) mutation. We also examined the benefit of including up to 10 additional CFTR mutations in the screening protocol. From 1985 to 1994, using either the IRT or IRT/DNA protocol, 220 862 and 104 308 neonates, respectively, were screened for CF. For the IRT protocol, neonates with an IRT >/=180 ng/mL were considered positive, and the standard sweat chloride test was administered to determine CF status. For the IRT/DNA protocol, samples from the original dried-blood specimen on the Guthrie card of neonates with an IRT >/=110 ng/mL were tested for the presence of the DeltaF508 CFTR allele, and if the DNA test revealed one or two DeltaF508 alleles, a sweat test was obtained. Both screening procedures had very high specificity. The sensitivity tended to be higher with the IRT/DNA protocol, but the differences were not statistically significant. The positive predictive value of the IRT/DNA screening protocol was 15.2% compared with 6.4% if the same samples had been screened by the IRT method. Assessment of the false-positive IRT/DNA population revealed that the two-tier method eliminates the disproportionate number of infants with low Apgar scores and also the high prevalence of African-Americans identified previously in our study of newborns with high IRT levels. We found that 55% of DNA-positive CF infants were homozygous for DeltaF508 and 40% had one DeltaF508 allele. Adding analyses for 10 more CFTR mutations has only a small effect on the sensitivity but is likely to add significantly to the cost of screening. Advantages of the IRT/DNA protocol over IRT analysis include improved positive predictive value, reduction of false-positive infants, and more rapid diagnosis with elimination of recall specimens.

New Method of Calibrating IRT Models.

ERIC Educational Resources Information Center

Jiang, Hai; Tang, K. Linda

This discussion of new methods for calibrating item response theory (IRT) models looks into new optimization procedures, such as the Genetic Algorithm (GA) to improve on the use of the Newton-Raphson procedure. The advantages of using a global optimization procedure like GA is that this kind of procedure is not easily affected by local optima and…

First and Higher Order Effects on Zero Order Radiative Transfer Model

NASA Astrophysics Data System (ADS)

Neelam, M.; Mohanty, B.

2014-12-01

Microwave radiative transfer model are valuable tool in understanding the complex land surface interactions. Past literature has largely focused on local sensitivity analysis for factor priotization and ignoring the interactions between the variables and uncertainties around them. Since land surface interactions are largely nonlinear, there always exist uncertainties, heterogeneities and interactions thus it is important to quantify them to draw accurate conclusions. In this effort, we used global sensitivity analysis to address the issues of variable uncertainty, higher order interactions, factor priotization and factor fixing for zero-order radiative transfer (ZRT) model. With the to-be-launched Soil Moisture Active Passive (SMAP) mission of NASA, it is very important to have a complete understanding of ZRT for soil moisture retrieval to direct future research and cal/val field campaigns. This is a first attempt to use GSA technique to quantify first order and higher order effects on brightness temperature from ZRT model. Our analyses reflect conditions observed during the growing agricultural season for corn and soybeans in two different regions in - Iowa, U.S.A and Winnipeg, Canada. We found that for corn fields in Iowa, there exist significant second order interactions between soil moisture, surface roughness parameters (RMS height and correlation length) and vegetation parameters (vegetation water content, structure and scattering albedo), whereas in Winnipeg, second order interactions are mainly due to soil moisture and vegetation parameters. But for soybean fields in both Iowa and Winnipeg, we found significant interactions only to exist between soil moisture and surface roughness parameters.

The IGF-1/cortisol ratio as a useful marker for monitoring training in young boxers

PubMed Central

Nassib, S; Moalla, W; Hammoudi-Nassib, S; Chtara, M; Hachana, Y; Tabka, Z; Chamari, K

2015-01-01

Training effects on plasma insulin-like growth factor-1 (IGF-1)/cortisol ratio were investigated in boxers. Thirty subjects were assigned to either the training or the control group (n = 15 in both). They were tested before the beginning of training (T0), after 5 weeks of intensive training (T1), and after 1 week of tapering (T2). Physical performances (Yo-Yo intermittent recovery test level-1), training loads, and blood sampling were obtained at T0, T1, and T2. Controls were only tested for biochemical and anthropometric parameters at T0 and T2. A significantly higher physical performance was observed at T2 compared to T1. At T1, cortisol levels were significantly increased whereas IGF-1 and insulin-like growth factor binding protein-3 (IGFBP-3) levels remained unchanged compared to baseline. At T2, cortisol levels decreased while IGF-1 and IGFBP-3 levels increased. The IGF-1/cortisol ratio decreased significantly at T1 and increased at T2, and its variations were significantly correlated with changes in training loads and Yo-Yo intermittent recovery test level 1 (IRT1) performance over the training period. Cortisol variations correlated with changes in training load (r = 0.64; p < 0.01) and Yo-Yo IRT1 performance (r = 0.78; p < 0.001) at T1 whereas IGF-1 variations correlated only with changes in Yo-Yo IRT1 performance at T2 (r = 0.71; p < 0.001). It is concluded that IGF-1/cortisol ratio could be a useful tool for monitoring training loads in young trained boxers. PMID:26985129

Variants in Solute Carrier SLC26A9 Modify Prenatal Exocrine Pancreatic Damage in Cystic Fibrosis

PubMed Central

Miller, Melissa R.; Soave, David; Li, Weili; Gong, Jiafen; Pace, Rhonda G.; Boëlle, Pierre-Yves; Cutting, Garry R.; Drumm, Mitchell L.; Knowles, Michael R.; Sun, Lei; Rommens, Johanna M.; Accurso, Frank; Durie, Peter R.; Corvol, Harriet; Levy, Hara; Sontag, Marci K.; Strug, Lisa J.

2015-01-01

Objectives To test the hypothesis that multiple constituents of the apical plasma membrane residing alongside the causal CF Transmembrane Conductance Regulator (CFTR) protein, including known cystic fibrosis (CF) modifiers SLC26A9, SLC6A14, and SLC9A3, would be associated with prenatal exocrine pancreatic damage as measured by newborn screened (NBS) IRT levels. Study design NBS IRT measures and genome-wide genotype data were available on 111 subjects from Colorado, 37 subjects from Wisconsin, and 80 subjects from France. Multiple linear regression was used to determine whether any of eight SNPs in SLC26A9, SLC6A14 and SLC9A3 were associated with IRT and whether other constituents of the apical plasma membrane contributed to IRT. Results In the Colorado sample, three SLC26A9 SNPs were associated with NBS IRT (min P = 1.16 × 10−3; rs7512462), but no SLC6A14 or SLC9A3 SNPs were associated (P > 0.05). The rs7512462 association replicated in the Wisconsin sample (P = 0.03) but not in the French sample (P = 0.76). Furthermore, rs7512462 was the top ranked apical membrane constituent in the combined Colorado and Wisconsin sample. Conclusions NBS IRT is a biomarker of prenatal exocrine pancreatic disease in patients with CF, and a SNP in SLC26A9 accounts for significant IRT variability. This suggests SLC26A9 as a potential therapeutic target to ameliorate exocrine pancreatic disease. PMID:25771386

Medical applications of infrared thermography: A review

NASA Astrophysics Data System (ADS)

Lahiri, B. B.; Bagavathiappan, S.; Jayakumar, T.; Philip, John

2012-07-01

Abnormal body temperature is a natural indicator of illness. Infrared thermography (IRT) is a fast, passive, non-contact and non-invasive alternative to conventional clinical thermometers for monitoring body temperature. Besides, IRT can also map body surface temperature remotely. Last five decades witnessed a steady increase in the utility of thermal imaging cameras to obtain correlations between the thermal physiology and skin temperature. IRT has been successfully used in diagnosis of breast cancer, diabetes neuropathy and peripheral vascular disorders. It has also been used to detect problems associated with gynecology, kidney transplantation, dermatology, heart, neonatal physiology, fever screening and brain imaging. With the advent of modern infrared cameras, data acquisition and processing techniques, it is now possible to have real time high resolution thermographic images, which is likely to surge further research in this field. The present efforts are focused on automatic analysis of temperature distribution of regions of interest and their statistical analysis for detection of abnormalities. This critical review focuses on advances in the area of medical IRT. The basics of IRT, essential theoretical background, the procedures adopted for various measurements and applications of IRT in various medical fields are discussed in this review. Besides background information is provided for beginners for better understanding of the subject.

Electronic signatures of dimerization in IrTe2

NASA Astrophysics Data System (ADS)

Dai, Jixia; Wu, Weida; Oh, Yoon Seok; Cheong, S.-W.; Yang, J. J.

2014-03-01

Recently, the mysterious phase transition around Tc ~ 260 K in IrTe2 has been intensively studied. A structural supermodulation with q =1/5 was identified below Tc. A variety of microscopic mechanisms have been proposed to account for this transition, including charge-density wave due to Fermi surface nesting, Te p-orbital driven structure instability, anionic depolymerization, ionic dimerization, and so on. However, there has not been an unified picture on the nature of this transition. To address this issue, we have performed low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) experiments on IrTe2 and IrTe2-xSex. Our STM data clearly shows a strong bias dependence in both topography and local density of states (STS) maps. High resolution spectroscopic data further confirms the stripe-like electronic states modulation, which provides insight to the ionic dimerization revealed by X-ray diffraction.

Stimulatory effects of bombesin on plasma trypsin release and exocrine pancreatic secretion in dogs.

PubMed

Kiriyama, S; Hayakawa, T; Kondo, T; Shibata, T; Kitagawa, M; Sakai, Y; Sobajima, H; Ikei, N; Kodaira, T; Hamaoka, T

1990-01-01

We examined the effect of bombesin on plasma trypsin release and exocrine pancreatic secretion in dogs. Bombesin significantly increased plasma immunoreactive trypsin (IRT). Atropine significantly inhibited the response of plasma IRT to bombesin. Pancreatic trypsin secretion was also increased by bombesin, as well as bicarbonate and protein outputs. Atropine failed to inhibit pancreatic trypsin secretion. In conclusion, bombesin has a stimulatory effect on plasma trypsin release mediated by a cholinergic mechanism and different from pancreatic secretion.

CRISPR/Cas9-Mediated Gene Disruption Reveals the Importance of Zinc Metabolism for Fitness of the Dimorphic Fungal Pathogen Blastomyces dermatitidis

PubMed Central

Kujoth, Gregory C.; Sullivan, Thomas D.; Merkhofer, Richard; Lee, Taek-Jin; Wang, Huafeng; Brandhorst, Tristan; Wüthrich, Marcel

2018-01-01

ABSTRACT Blastomyces dermatitidis is a human fungal pathogen of the lung that can lead to disseminated disease in healthy and immunocompromised individuals. Genetic analysis of this fungus is hampered by the relative inefficiency of traditional recombination-based gene-targeting approaches. Here, we demonstrate the feasibility of applying CRISPR/Cas9-mediated gene editing to Blastomyces, including to simultaneously target multiple genes. We created targeting plasmid vectors expressing Cas9 and either one or two single guide RNAs and introduced these plasmids into Blastomyces via Agrobacterium gene transfer. We succeeded in disrupting several fungal genes, including PRA1 and ZRT1, which are involved in scavenging and uptake of zinc from the extracellular environment. Single-gene-targeting efficiencies varied by locus (median, 60% across four loci) but were approximately 100-fold greater than traditional methods of Blastomyces gene disruption. Simultaneous dual-gene targeting proceeded with efficiencies similar to those of single-gene-targeting frequencies for the respective targets. CRISPR/Cas9 disruption of PRA1 or ZRT1 had a variable impact on growth under zinc-limiting conditions, showing reduced growth at early time points in low-passage-number cultures and growth similar to wild-type levels by later passage. Individual impairment of PRA1 or ZRT1 resulted in a reduction of the fungal burden in a mouse model of Blastomyces infection by a factor of ~1 log (range, up to 3 logs), and combined disruption of both genes had no additional impact on the fungal burden. These results underscore the utility of CRISPR/Cas9 for efficient gene disruption in dimorphic fungi and reveal a role for zinc metabolism in Blastomyces fitness in vivo. PMID:29615501

IRTs of the ABCs: Children's Letter Name Acquisition

PubMed Central

Piasta, Shayne B.; Anthony, Jason L.; Lonigan, Christopher J.; Francis, David J.

2015-01-01

We examined the developmental sequence of letter name knowledge acquisition by children from 2 to five years of age. Data from 2 samples representing diverse regions, ethnicity, and socioeconomic backgrounds (ns = 1074 & 500) were analyzed using item response theory (IRT) and differential item functioning techniques. Results from factor analyses indicated that letter name knowledge represented a unidimensional skill; IRT results yielded significant differences between letters in both difficulty and discrimination. Results also indicated an approximate developmental sequence in letter name learning for the simplest and most challenging to learn letters -- but with no clear sequence between these extremes. Findings also suggested that children were most likely to first learn their first initial. We discuss implications for assessment and instruction. PMID:22710016

Robust Measurement via A Fused Latent and Graphical Item Response Theory Model.

PubMed

Chen, Yunxiao; Li, Xiaoou; Liu, Jingchen; Ying, Zhiliang

2018-03-12

Item response theory (IRT) plays an important role in psychological and educational measurement. Unlike the classical testing theory, IRT models aggregate the item level information, yielding more accurate measurements. Most IRT models assume local independence, an assumption not likely to be satisfied in practice, especially when the number of items is large. Results in the literature and simulation studies in this paper reveal that misspecifying the local independence assumption may result in inaccurate measurements and differential item functioning. To provide more robust measurements, we propose an integrated approach by adding a graphical component to a multidimensional IRT model that can offset the effect of unknown local dependence. The new model contains a confirmatory latent variable component, which measures the targeted latent traits, and a graphical component, which captures the local dependence. An efficient proximal algorithm is proposed for the parameter estimation and structure learning of the local dependence. This approach can substantially improve the measurement, given no prior information on the local dependence structure. The model can be applied to measure both a unidimensional latent trait and multidimensional latent traits.

A Review of PROC IRT in SAS

ERIC Educational Resources Information Center

Choi, Jinnie

2017-01-01

This article reviews PROC IRT, which was added to Statistical Analysis Software in 2014. We provide an introductory overview of a free version of SAS, describe what PROC IRT offers for item response theory (IRT) analysis and how one can use PROC IRT, and discuss how other SAS macros and procedures may compensate the IRT functionalities of PROC IRT.

Is there a strategy I iron uptake mechanism in maize?

PubMed

Li, Suzhen; Zhou, Xiaojin; Chen, Jingtang; Chen, Rumei

2018-04-03

Iron is a metal micronutrient that is essential for plant growth and development. Graminaceous and nongraminaceous plants have evolved different mechanisms to mediate Fe uptake. Generally, strategy I is used by nongraminaceous plants like Arabidopsis, while graminaceous plants, such as rice, barley, and maize, are considered to use strategy II Fe uptake. Upon the functional characterization of OsIRT1 and OsIRT2 in rice, it was suggested that rice, as an exceptional graminaceous plant, utilizes both strategy I and strategy II Fe uptake systems. Similarly, ZmIRT1 and ZmZIP3 were identified as functional zinc and iron transporters in the maize genome, along with the determination of several genes encoding Zn and Fe transporters, raising the possibility that strategy I Fe uptake also occurs in maize. This mini-review integrates previous reports and recent evidence to obtain a better understanding of the mechanisms of Fe uptake in maize.

Improving the Sensitivity and Positive Predictive Value in a Cystic Fibrosis Newborn Screening Program Using a Repeat Immunoreactive Trypsinogen and Genetic Analysis.

PubMed

Sontag, Marci K; Lee, Rachel; Wright, Daniel; Freedenberg, Debra; Sagel, Scott D

2016-08-01

To evaluate the performance of a new cystic fibrosis (CF) newborn screening algorithm, comprised of immunoreactive trypsinogen (IRT) in first (24-48 hours of life) and second (7-14 days of life) dried blood spot plus DNA on second dried blood spot, over existing algorithms. A retrospective review of the IRT/IRT/DNA algorithm implemented in Colorado, Wyoming, and Texas. A total of 1 520 079 newborns were screened, 32 557 (2.1%) had abnormal first IRT; 8794 (0.54%) on second. Furthermore, 14 653 mutation analyses were performed; 1391 newborns were referred for diagnostic testing; 274 newborns were diagnosed; and 201/274 (73%) of newborns had 2 mutations on the newborn screening CFTR panel. Sensitivity was 96.2%, compared with sensitivity of 76.1% observed with IRT/IRT (105 ng/mL cut-offs, P < .0001). The ratio of newborns with CF to heterozygote carriers was 1:2.5, and newborns with CF to newborns with CFTR-related metabolic syndrome was 10.8:1. The overall positive predictive value was 20%. The median age of diagnosis was 28, 30, and 39.5 days in the 3 states. IRT/IRT/DNA is more sensitive than IRT/IRT because of lower cut-offs (∼97 percentile or 60 ng/mL); higher cut-offs in IRT/IRT programs (>99 percentile, 105 ng/mL) would not achieve sufficient sensitivity. Carrier identification and identification of newborns with CFTR-related metabolic syndrome is less common in IRT/IRT/DNA compared with IRT/DNA. The time to diagnosis is nominally longer, but diagnosis can be achieved in the neonatal period and opportunities to further improve timeliness have been enacted. IRT/IRT/DNA algorithm should be considered by programs with 2 routine screens. Copyright © 2016 Elsevier Inc. All rights reserved.

PROC IRT: A SAS Procedure for Item Response Theory

PubMed Central

Matlock Cole, Ki; Paek, Insu

2017-01-01

This article reviews the procedure for item response theory (PROC IRT) procedure in SAS/STAT 14.1 to conduct item response theory (IRT) analyses of dichotomous and polytomous datasets that are unidimensional or multidimensional. The review provides an overview of available features, including models, estimation procedures, interfacing, input, and output files. A small-scale simulation study evaluates the IRT model parameter recovery of the PROC IRT procedure. The use of the IRT procedure in Statistical Analysis Software (SAS) may be useful for researchers who frequently utilize SAS for analyses, research, and teaching.

Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar (Eifel, Germany)

NASA Astrophysics Data System (ADS)

Römer, Wolfgang; Lehmkuhl, Frank; Sirocko, Frank

2016-12-01

The study presents the results of a heavy mineral analysis from a 38 m long record of lacustrine Eifel maar sediments from a core section of the Dehner dry maar. The record encompasses the period from 29,000 to about 12,500 b2k. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size Index (GSI and CSI). The results indicate that during the early stages of MIS2 (39 to 30 m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by low GSI and CSI ratios resulting from a reduced mobility of material due to a vegetation cover. The period between 23,000 and 12,900 b2k is characterized by a higher supply of heavy minerals from regional and more distant sources. Changes in the provenance areas are indicated in inverse relationships between zircon, rutile, tourmaline (ZRT) and carbonate particles. Shifts in the wind direction are documented in pronounced peaks of carbonate particles indicating easterly winds that have crossed the limestone basins in the Eifeler North South Zone. ZRT-group minerals on the other hand suggest a westerly source area from Palaeozoic clastic sedimentary rocks. The heavy mineral assemblage of the LGM section at 23,000 to 15,000 b2k displays a close correspondence with the stratigraphic relationships that have been obtained for the Landscape Evolution Zone 4 of the ELSA-Vegetation Stack of Sirocko et al. (2016). From the Heinrich 2 event onwards the analyses indicate an increasing degree of mixing of heavy minerals from various provinces. This suggests the existence of a presumably incomplete, thin cover of deflated loess-like sediments that has been repeatedly reworked on the elevated surfaces of the Eifel.

Validity of the 30-15 Intermittent Fitness Test in Subelite Female Athletes.

PubMed

Bruce, Lyndell M; Moule, Simon J

2017-11-01

Bruce, LM and Moule, SJ. Validity of the 30-15 intermittent fitness test in subelite female athletes. J Strength Cond Res 31(11): 3077-3082, 2017-The purpose of this study was to assess the suitability of the 30-15 Intermittent Fitness Test (IFT) as a test in netball using female athletes. Twenty-six female subelite netballers (mean age = 19.7 ± 4.6 years, mean height = 176.0 ± 6.1 cm, mean body mass = 69.7 ± 9.3 kg) completed the yo-yo intermittent recovery test level 1 (yo-yo IRT1) and the 30-15 IFT. Participants performed both assessments 1 week apart before the intervention and both tests 1 week apart after the training intervention (for a total of 4 testing sessions). A 6-week training intervention occurred between the test occasions. Pearson's correlations revealed significant very strong relationships between the 30-15 IFT and yo-yo IRT on both test occasions (test occasion 1: r = 0.71, p = 0.003 [95% confidence interval {CI} 0.35-0.89], magnitude of effect, most likely; test occasion 2: r = 0.72, p = 0.001 [95% CI: 0.42-0.88], magnitude of effect, most likely). Repeated-measures analysis of variances examining the effect of position on performance changes revealed main effects for test occasion and a position × test occasion interaction for both the 30-15 IFT and the yo-yo IRT1 (30-15 IFT: test occasion [F(1,14) = 28.68, p = 0.001, ηp = 0.67], position × test occasion interaction [F(2,14) = 9.38, p = 0.003, ηp = 0.57]; yo-yo IRT1: test occasion [F(1,15) = 11.72, p = 0.004, ηp = 0.44], position × test occasion interaction [F(2,15) = 9.96, p = 0.002, ηp = 0.57]). Results show that the 30-15 IFT is a suitable test for female netballers as it was able to detect improvements in performance after a training intervention, in addition to having a very strong significant relationship with the yo-yo IRT1.

Gastrin: The Test

MedlinePlus

... Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy hCG Tumor Marker HDL Cholesterol ... Immunoreactive Trypsinogen (IRT) Influenza Tests Insulin Insulin-like Growth Factor-1 ... Hormone (LH) Lyme Disease Tests Magnesium Maternal Serum Screening, ...

Rheumatoid Factor

MedlinePlus

... Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy hCG Tumor Marker HDL Cholesterol ... Immunoreactive Trypsinogen (IRT) Influenza Tests Insulin Insulin-like Growth Factor-1 ... Hormone (LH) Lyme Disease Tests Magnesium Maternal Serum Screening, ...

Antithrombin Test

MedlinePlus

... Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy hCG Tumor Marker HDL Cholesterol ... Immunoreactive Trypsinogen (IRT) Influenza Tests Insulin Insulin-like Growth Factor-1 ... Hormone (LH) Lyme Disease Tests Magnesium Maternal Serum Screening, ...

Understanding Your Tests

MedlinePlus

... Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy hCG Tumor Marker HDL Cholesterol ... Immunoreactive Trypsinogen (IRT) Influenza Tests Insulin Insulin-like Growth Factor-1 ... Hormone (LH) Lyme Disease Tests Magnesium Maternal Serum Screening, ...

Direct Antiglobulin Test

MedlinePlus

... Cancer Therapy Glucose Tests Gonorrhea Testing Gram Stain Growth Hormone Haptoglobin hCG Pregnancy hCG Tumor Marker HDL Cholesterol ... Immunoreactive Trypsinogen (IRT) Influenza Tests Insulin Insulin-like Growth Factor-1 ... Hormone (LH) Lyme Disease Tests Magnesium Maternal Serum Screening, ...

A Decision-Tree Approach to Cost Comparison of Newborn Screening Strategies for Cystic Fibrosis

PubMed Central

Wells, Janelle; Rosenberg, Marjorie; Hoffman, Gary; Anstead, Michael

2012-01-01

OBJECTIVE: Because cystic fibrosis can be difficult to diagnose and treat early, newborn screening programs have rapidly developed nationwide but methods vary widely. We therefore investigated the costs and consequences or specific outcomes of the 2 most commonly used methods. METHODS: With available data on screening and follow-up, we used a simulation approach with decision trees to compare immunoreactive trypsinogen (IRT) screening followed by a second IRT test against an IRT/DNA analysis. By using a Monte Carlo simulation program, variation in the model parameters for counts at various nodes of the decision trees, as well as for costs, are included and applied to fictional cohorts of 100 000 newborns. The outcome measures included the numbers of newborns given a diagnosis of cystic fibrosis and costs of screening strategy at each branch and cost per newborn. RESULTS: Simulations revealed a substantial number of potential missed diagnoses for the IRT/IRT system versus IRT/DNA. Although the IRT/IRT strategy with commonly used cutoff values offers an average overall cost savings of $2.30 per newborn, a breakdown of costs by societal segments demonstrated higher out-of-pocket costs for families. Two potential system failures causing delayed diagnoses were identified relating to the screening protocols and the follow-up system. CONCLUSIONS: The IRT/IRT screening algorithm reduces the costs to laboratories and insurance companies but has more system failures. IRT/DNA offers other advantages, including fewer delayed diagnoses and lower out-of-pocket costs to families. PMID:22291119

Modern psychometrics applied in rheumatology--a systematic review.

PubMed

Siemons, Liseth; Ten Klooster, Peter M; Taal, Erik; Glas, Cees Aw; Van de Laar, Mart Afj

2012-10-31

Although item response theory (IRT) appears to be increasingly used within health care research in general, a comprehensive overview of the frequency and characteristics of IRT analyses within the rheumatic field is lacking. An overview of the use and application of IRT in rheumatology to date may give insight into future research directions and highlight new possibilities for the improvement of outcome assessment in rheumatic conditions. Therefore, this study systematically reviewed the application of IRT to patient-reported and clinical outcome measures in rheumatology. Literature searches in PubMed, Scopus and Web of Science resulted in 99 original English-language articles which used some form of IRT-based analysis of patient-reported or clinical outcome data in patients with a rheumatic condition. Both general study information and IRT-specific information were assessed. Most studies used Rasch modeling for developing or evaluating new or existing patient-reported outcomes in rheumatoid arthritis or osteoarthritis patients. Outcomes of principle interest were physical functioning and quality of life. Since the last decade, IRT has also been applied to clinical measures more frequently. IRT was mostly used for evaluating model fit, unidimensionality and differential item functioning, the distribution of items and persons along the underlying scale, and reliability. Less frequently used IRT applications were the evaluation of local independence, the threshold ordering of items, and the measurement precision along the scale. IRT applications have markedly increased within rheumatology over the past decades. To date, IRT has primarily been applied to patient-reported outcomes, however, applications to clinical measures are gaining interest. Useful IRT applications not yet widely used within rheumatology include the cross-calibration of instrument scores and the development of computerized adaptive tests which may reduce the measurement burden for both the patient and the clinician. Also, the measurement precision of outcome measures along the scale was only evaluated occasionally. Performed IRT analyses should be adequately explained, justified, and reported. A global consensus about uniform guidelines should be reached concerning the minimum number of assumptions which should be met and best ways of testing these assumptions, in order to stimulate the quality appraisal of performed IRT analyses.

Remote sensing of multiple vital signs using a CMOS camera-equipped infrared thermography system and its clinical application in rapidly screening patients with suspected infectious diseases.

PubMed

Sun, Guanghao; Nakayama, Yosuke; Dagdanpurev, Sumiyakhand; Abe, Shigeto; Nishimura, Hidekazu; Kirimoto, Tetsuo; Matsui, Takemi

2017-02-01

Infrared thermography (IRT) is used to screen febrile passengers at international airports, but it suffers from low sensitivity. This study explored the application of a combined visible and thermal image processing approach that uses a CMOS camera equipped with IRT to remotely sense multiple vital signs and screen patients with suspected infectious diseases. An IRT system that produced visible and thermal images was used for image acquisition. The subjects' respiration rates were measured by monitoring temperature changes around the nasal areas on thermal images; facial skin temperatures were measured simultaneously. Facial blood circulation causes tiny color changes in visible facial images that enable the determination of the heart rate. A logistic regression discriminant function predicted the likelihood of infection within 10s, based on the measured vital signs. Sixteen patients with an influenza-like illness and 22 control subjects participated in a clinical test at a clinic in Fukushima, Japan. The vital-sign-based IRT screening system had a sensitivity of 87.5% and a negative predictive value of 91.7%; these values are higher than those of conventional fever-based screening approaches. Multiple vital-sign-based screening efficiently detected patients with suspected infectious diseases. It offers a promising alternative to conventional fever-based screening. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

The components of the unique Zur regulon of Cupriavidus metallidurans mediate cytoplasmic zinc handling.

PubMed

Bütof, Lucy; Schmidt-Vogler, Christopher; Herzberg, Martin; Große, Cornelia; Nies, Dietrich H

2017-08-14

Zinc is an essential trace element and at the same time it is toxic at high concentrations. In the beta-proteobacterium Cupriavidus metallidurans the highly efficient removal of surplus zinc from the periplasm is responsible for its outstanding metal resistance. Rather than having a typical Zur-dependent, high-affinity ATP-binding cassette transporter of the ABC protein superfamily for zinc uptake at low concentrations, C. metallidurans instead has the secondary zinc importer ZupT of the ZRT/IRT (ZIP) family. It is important to understand, therefore, how this zinc-resistant bacterium copes when it is exposed to low zinc concentrations. Members of the Zur regulon in C. metallidurans were identified by comparing the transcriptomes of a Δ zur mutant and its parent strain. The consensus sequence of the Zur-binding box was derived for the zupTp promoter-regulatory region using a truncation assay. The motif was used to predict possible Zur-boxes upstream of Zur regulon members. Binding of Zur to these boxes was confirmed. Two Zur-boxes upstream of the cobW 1 gene, encoding a putative zinc chaperone, proved to be required for complete repression of cobW 1 and its downstream genes in cells cultivated in mineral salts medium. A Zur box upstream of each of zur-cobW 2 , cobW 3 and zupT permitted low-expression level of these genes plus their up-regulation under zinc starvation conditions. This demonstrates a compartmentalization of zinc homeostasis in C. metallidurans with the periplasm being responsible for removal of surplus zinc and cytoplasmic components for management of zinc as an essential co-factor, with both compartments connected by ZupT. Importance Elucidating zinc homeostasis is necessary to understand both host-pathogen interactions and performance of free-living bacteria in their natural environment. Escherichia coli acquires zinc under low zinc concentrations by the Zur-controlled ZnuABC importer of the ABC superfamily, and this was also the paradigm for other bacteria. In contrast, the heavy metal-resistant bacterium C. metallidurans achieves high tolerance to zinc due to sophisticated zinc handling and efflux systems operating on periplasmic zinc ions, so that removal of surplus zinc is a periplasmic feature in this bacterium. It is shown here that this process is augmented by management of zinc through cytoplasmic zinc chaperones, whose syntheses are controlled by the Zur regulator. This demonstrates a new mechanism to organize zinc homeostasis through compartmentalization. Copyright © 2017 American Society for Microbiology.

Methodological issues regarding power of classical test theory (CTT) and item response theory (IRT)-based approaches for the comparison of patient-reported outcomes in two groups of patients - a simulation study

PubMed Central

2010-01-01

Background Patients-Reported Outcomes (PRO) are increasingly used in clinical and epidemiological research. Two main types of analytical strategies can be found for these data: classical test theory (CTT) based on the observed scores and models coming from Item Response Theory (IRT). However, whether IRT or CTT would be the most appropriate method to analyse PRO data remains unknown. The statistical properties of CTT and IRT, regarding power and corresponding effect sizes, were compared. Methods Two-group cross-sectional studies were simulated for the comparison of PRO data using IRT or CTT-based analysis. For IRT, different scenarios were investigated according to whether items or person parameters were assumed to be known, to a certain extent for item parameters, from good to poor precision, or unknown and therefore had to be estimated. The powers obtained with IRT or CTT were compared and parameters having the strongest impact on them were identified. Results When person parameters were assumed to be unknown and items parameters to be either known or not, the power achieved using IRT or CTT were similar and always lower than the expected power using the well-known sample size formula for normally distributed endpoints. The number of items had a substantial impact on power for both methods. Conclusion Without any missing data, IRT and CTT seem to provide comparable power. The classical sample size formula for CTT seems to be adequate under some conditions but is not appropriate for IRT. In IRT, it seems important to take account of the number of items to obtain an accurate formula. PMID:20338031

A quantitative comparison of noise reduction across five commercial (hybrid and model-based) iterative reconstruction techniques: an anthropomorphic phantom study.

PubMed

Patino, Manuel; Fuentes, Jorge M; Hayano, Koichi; Kambadakone, Avinash R; Uyeda, Jennifer W; Sahani, Dushyant V

2015-02-01

OBJECTIVE. The objective of our study was to compare the performance of three hybrid iterative reconstruction techniques (IRTs) (ASiR, iDose4, SAFIRE) and their respective strengths for image noise reduction on low-dose CT examinations using filtered back projection (FBP) as the standard reference. Also, we compared the performance of these three hybrid IRTs with two model-based IRTs (Veo and IMR) for image noise reduction on low-dose examinations. MATERIALS AND METHODS. An anthropomorphic abdomen phantom was scanned at 100 and 120 kVp and different tube current-exposure time products (25-100 mAs) on three CT systems (for ASiR and Veo, Discovery CT750 HD; for iDose4 and IMR, Brilliance iCT; and for SAFIRE, Somatom Definition Flash). Images were reconstructed using FBP and using IRTs at various strengths. Nine noise measurements (mean ROI size, 423 mm(2)) on extracolonic fat for the different strengths of IRTs were recorded and compared with FBP using ANOVA. Radiation dose, which was measured as the volume CT dose index and dose-length product, was also compared. RESULTS. There were no significant differences in radiation dose and image noise among the scanners when FBP was used (p > 0.05). Gradual image noise reduction was observed with each increasing increment of hybrid IRT strength, with a maximum noise suppression of approximately 50% (48.2-53.9%). Similar noise reduction was achieved on the scanners by applying specific hybrid IRT strengths. Maximum noise reduction was higher on model-based IRTs (68.3-81.1%) than hybrid IRTs (48.2-53.9%) (p < 0.05). CONCLUSION. When constant scanning parameters are used, radiation dose and image noise on FBP are similar for CT scanners made by different manufacturers. Significant image noise reduction is achieved on low-dose CT examinations rendered with IRTs. The image noise on various scanners can be matched by applying specific hybrid IRT strengths. Model-based IRTs attain substantially higher noise reduction than hybrid IRTs irrespective of the radiation dose.

First results of infrared thermography applied to the evaluation of hydraulic conductivity in rock masses

NASA Astrophysics Data System (ADS)

Pappalardo, Giovanna

2018-03-01

An innovative methodological approach using infrared thermography (IRT) provides a potential contribution to the indirect assessment of hydraulic conductivity of jointed rock masses. This technique proved a suitable tool to evaluate the degree of fracturing of rock masses along with their discontinuity systems, which expedite water flow within the rock mass itself. First, based on the latest scientific outcomes on the application of IRT to the geomechanics of rock systems, rock mass surveys were carried out at different outcrops (dolostone, limestone and porphyroid) and hydraulic conductivity was empirically assessed through approaches well known in the international literature. Then, IRT campaigns were performed at each surveyed rock mass, with the purpose of evaluating the corresponding Cooling Rate Index, strictly linked to the cooling attitude of the rock. Such index was correlated with the assessed hydraulic conductivity and satisfactory regression equations were achieved. The interesting results show that hydraulic conductivity values are likely to be linked with the cooling behavior of rock masses, which, in turn, is affected by spacing, aperture and persistence of discontinuities.

The Exploration of the Relationship between Guessing and Latent Ability in IRT Models

ERIC Educational Resources Information Center

Gao, Song

2011-01-01

This study explored the relationship between successful guessing and latent ability in IRT models. A new IRT model was developed with a guessing function integrating probability of guessing an item correctly with the examinee's ability and the item parameters. The conventional 3PL IRT model was compared with the new 2PL-Guessing model on…

Comparing Vertical Scales Derived from Dichotomous and Polytomous IRT Models for a Test Composed of Testlets.

ERIC Educational Resources Information Center

Bishop, N. Scott; Omar, Md Hafidz

Previous research has shown that testlet structures often violate important assumptions of dichotomous item response theory (D-IRT) models, applied to item-level scores, that can in turn affect the results of many measurement applications. In this situation, polytomous IRT (P-IRT) models, applied to testlet-level scores, have been used as an…

A Unified Approach to IRT Scale Linking and Scale Transformations. Research Report. RR-04-09

ERIC Educational Resources Information Center

von Davier, Matthias; von Davier, Alina A.

2004-01-01

This paper examines item response theory (IRT) scale transformations and IRT scale linking methods used in the Non-Equivalent Groups with Anchor Test (NEAT) design to equate two tests, X and Y. It proposes a unifying approach to the commonly used IRT linking methods: mean-mean, mean-var linking, concurrent calibration, Stocking and Lord and…

EXPRESSION OF THE IRT1 METAL TRANSPORTER IS CONTROLLED BY METALS AT THE LEVELS OF TRANSCRIPT AND PROTEIN ACCUMULATION. (R827612E02)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

A Targeted MRM Approach for Tempo-Spatial Proteomics Analyses.

PubMed

Moradian, Annie; Porras-Yakushi, Tanya R; Sweredoski, Michael J; Hess, Sonja

2016-01-01

When deciding to perform a quantitative proteomics analysis, selectivity, sensitivity, and reproducibility are important criteria to consider. The use of multiple reaction monitoring (MRM) has emerged as a powerful proteomics technique in that regard since it avoids many of the problems typically observed in discovery-based analyses. A prerequisite for such a targeted approach is that the protein targets are known, either as a result of previous global proteomics experiments or because a specific hypothesis is to be tested. When guidelines that have been established in the pharmaceutical industry many decades ago are taken into account, setting up an MRM assay is relatively straightforward. Typically, proteotypic peptides with favorable mass spectrometric properties are synthesized with a heavy isotope for each protein that is to be monitored. Retention times and calibration curves are determined using triple-quadrupole mass spectrometers. The use of iRT peptide standards is both recommended and fully integrated into the bioinformatics pipeline. Digested biological samples are mixed with the heavy and iRT standards and quantified. Here we present a generic protocol for the development of an MRM assay.

Clinical Application Of Advanced Infrared Thermography (IRT) In Locomotor Diseases

NASA Astrophysics Data System (ADS)

Engel, Joachim-Michael

1983-11-01

Locomotor diseases is a wide range of about 450 different illnesses with all different pathologies, clinical and prognostic features and response to treatment. No single method will be able to cover the whole spectrum of local and systemic signs and symptoms. Nevertheless there is a need for objective measurements at the site of disease: clinical examination is often enough depending from subjective estimations and personal experiance of the clinician. Laboratory tests only show the systemic effect of the disease, like inflammation. X-rays are restricted to the detection of structural changes appearing late during the pathological process, even when using different techniques. Here IRT offers several advantages to the clinician as well as to the patient. As a non invasive method it monitors the course of disease at the anatomic site of pathology. Quantitative figures calculated from the thermogram,either taken at steady-state or during dynamic tests, are essential for differential diagnosis and follow-up. Advanced IRT camera systems fulfill all requirements set up for medical thermography recently by the National Bureau of Standards. Although, the user should check his system daily with regard to precision of absolute temperature measurements. Standardisation of recording technique is essential as well,to get reliable results. Ambient conditions must be adapted to the locomotor disease pathology under study. Advanced IRT systems , e.g. ZEISS-IKOTHERM, together with image processing capability and special software, e.g. THERMOTOM package, are valuable tools to the rheumatologist for diagnosing and monitoring locomotor diseases.

Practical Consequences of Item Response Theory Model Misfit in the Context of Test Equating with Mixed-Format Test Data

PubMed Central

Zhao, Yue; Hambleton, Ronald K.

2017-01-01

In item response theory (IRT) models, assessing model-data fit is an essential step in IRT calibration. While no general agreement has ever been reached on the best methods or approaches to use for detecting misfit, perhaps the more important comment based upon the research findings is that rarely does the research evaluate IRT misfit by focusing on the practical consequences of misfit. The study investigated the practical consequences of IRT model misfit in examining the equating performance and the classification of examinees into performance categories in a simulation study that mimics a typical large-scale statewide assessment program with mixed-format test data. The simulation study was implemented by varying three factors, including choice of IRT model, amount of growth/change of examinees’ abilities between two adjacent administration years, and choice of IRT scaling methods. Findings indicated that the extent of significant consequences of model misfit varied over the choice of model and IRT scaling methods. In comparison with mean/sigma (MS) and Stocking and Lord characteristic curve (SL) methods, separate calibration with linking and fixed common item parameter (FCIP) procedure was more sensitive to model misfit and more robust against various amounts of ability shifts between two adjacent administrations regardless of model fit. SL was generally the least sensitive to model misfit in recovering equating conversion and MS was the least robust against ability shifts in recovering the equating conversion when a substantial degree of misfit was present. The key messages from the study are that practical ways are available to study model fit, and, model fit or misfit can have consequences that should be considered when choosing an IRT model. Not only does the study address the consequences of IRT model misfit, but also it is our hope to help researchers and practitioners find practical ways to study model fit and to investigate the validity of particular IRT models for achieving a specified purpose, to assure that the successful use of the IRT models are realized, and to improve the applications of IRT models with educational and psychological test data. PMID:28421011

Experimental study on infrared radiation temperature field of concrete under uniaxial compression

NASA Astrophysics Data System (ADS)

Lou, Quan; He, Xueqiu

2018-05-01

Infrared thermography, as a nondestructive, non-contact and real-time monitoring method, has great significance in assessing the stability of concrete structure and monitoring its failure. It is necessary to conduct in depth study on the mechanism and application of infrared radiation (IR) of concrete failure under loading. In this paper, the concrete specimens with size of 100 × 100 × 100 mm were adopted to carry out the uniaxial compressions for the IR tests. The distribution of IR temperatures (IRTs), surface topography of IRT field and the reconstructed IR images were studied. The results show that the IRT distribution follows the Gaussian distribution, and the R2 of Gaussian fitting changes along with the loading time. The abnormities of R2 and AE counts display the opposite variation trends. The surface topography of IRT field is similar to the hyperbolic paraboloid, which is related to the stress distribution in the sample. The R2 of hyperbolic paraboloid fitting presents an upward trend prior to the fracture which enables to change the IRT field significantly. This R2 has a sharp drop in response to this large destruction. The normalization images of IRT field, including the row and column normalization images, were proposed as auxiliary means to analyze the IRT field. The row and column normalization images respectively show the transverse and longitudinal distribution of the IRT field, and they have clear responses to the destruction occurring on the sample surface. In this paper, the new methods and quantitative index were proposed for the analysis of IRT field, which have some theoretical and instructive significance for the analysis of the characteristics of IRT field, as well as the monitoring of instability and failure for concrete structure.

Imagery rehearsal therapy in addition to treatment as usual for patients with diverse psychiatric diagnoses suffering from nightmares: a randomized controlled trial.

PubMed

van Schagen, Annette M; Lancee, Jaap; de Groot, Izaäk W; Spoormaker, Victor I; van den Bout, Jan

2015-09-01

Nightmares are associated with psychopathology and daily distress. They are highly prevalent in a psychiatric population (30%). Currently, imagery rehearsal therapy (IRT) is the treatment of choice for nightmares. With IRT, the script of the nightmare is changed into a new dream, which is imagined during the day. However, the effects of IRT in a psychiatric population remain unknown. The aim of this study was to determine the effectiveness of IRT in a heterogeneous psychiatric population. Between January 2006 and July 2010, 90 patients with psychiatric disorders (DSM-IV-TR) were randomized to IRT or treatment-as-usual conditions. IRT consisted of 6 individual sessions added to the treatment as usual. Nightmare frequency was assessed using daily nightmare logs and the Nightmare Frequency Questionnaire. Nightmare distress was assessed using the Nightmare Distress Questionnaire and the Nightmare Effects Survey. General psychiatric symptoms were assessed using the Symptom Checklist-90 and a PTSD symptom questionnaire. Assessments were administered at the start of the trial, after the IRT and at follow-up 3 months later. IRT showed a moderate effect (Cohen d = 0.5-0.7, P < .05) on nightmare frequency, nightmare distress, and psychopathology measures compared with treatment as usual. These effects were largely sustained at the 3-month follow-up (Cohen d = 0.4-0.6, P < .10). IRT is an effective treatment for nightmares among patients with comorbid psychiatric disorders and can be employed in addition to the on-going treatment. ClinicalTrials.gov identifier: NCT00291031. © Copyright 2015 Physicians Postgraduate Press, Inc.

A dynamic Thurstonian item response theory of motive expression in the picture story exercise: solving the internal consistency paradox of the PSE.

PubMed

Lang, Jonas W B

2014-07-01

The measurement of implicit or unconscious motives using the picture story exercise (PSE) has long been a target of debate in the psychological literature. Most debates have centered on the apparent paradox that PSE measures of implicit motives typically show low internal consistency reliability on common indices like Cronbach's alpha but nevertheless predict behavioral outcomes. I describe a dynamic Thurstonian item response theory (IRT) model that builds on dynamic system theories of motivation, theorizing on the PSE response process, and recent advancements in Thurstonian IRT modeling of choice data. To assess the models' capability to explain the internal consistency paradox, I first fitted the model to archival data (Gurin, Veroff, & Feld, 1957) and then simulated data based on bias-corrected model estimates from the real data. Simulation results revealed that the average squared correlation reliability for the motives in the Thurstonian IRT model was .74 and that Cronbach's alpha values were similar to the real data (<.35). These findings suggest that PSE motive measures have long been reliable and increase the scientific value of extant evidence from motivational research using PSE motive measures. (c) 2014 APA, all rights reserved.

Age Discrimination by Local Governmental Entities--The Defense of a Bona Fide Occupational Qualification.

ERIC Educational Resources Information Center

Hujar, Frances B.

1979-01-01

The bona fide occupational qualification defense is interpreted narrowly and is most likely to be applied in job situations that involve the safety of others. Available from Baylor Law Review, B.U. Station, Box 6262, Waco, TX 76706. (Author/IRT)

Calibration and tests of commercial wireless infrared thermometers

USDA-ARS?s Scientific Manuscript database

Applications of infrared thermometers (IRTs) in large agricultural fields require wireless data transmission, and IRT target temperature should have minimal sensitivity to internal detector temperature. To meet these objectives, a prototype wireless IRT system was developed at USDA Agricultural Rese...

Going Places No Infrared Temperature Devices Have Gone Before

NASA Technical Reports Server (NTRS)

2003-01-01

Exergen's IRt/c is a self-powered sensor that matches a thermocouple within specified temperature ranges and provides a predictable and repeatable signal outside of this specified range. Possessing an extremely fast time constant, the infrared technology allows users to measure product temperature without touching the product. The IRt/c uses a device called a thermopile to measure temperature and generate current. Traditionally, these devices are not available in a size that would be compatible with the Exergen IRt/c, based on NASA s quarterinch specifications. After going through five circuit designs to find a thermopile that would suit the IRt/c design and match the signal needed for output, Exergen maintains that it developed a model that totaled just 20 percent of the volume of the previous smallest detector in the world. Following completion of the project with Glenn, Exergen continued development of the IRt/c for other customers, spinning off a new product line called the micro IRt/c. This latest development has broadened applications for industries that previously could not use infrared thermometers due to size constraints. The first commercial use of the micro IRt/c involved an original equipment manufacturer that makes laminating machinery consisting of heated rollers in very tight spots. Accurate temperature measurement for this application requires close proximity to the heated rollers. With the micro IRt/c s 50-millisecond time constant, the manufacturer is able to gain closer access to the intended temperature targets for exact readings, thereby increasing productivity and staying ahead of competition.In a separate application, the infrared temperature sensor is being utilized for avalanche warnings in Switzerland. The IRt/c is mounted about 5 meters above the ground to measure the snow cover throughout the mountainous regions of the country.

Testing item response theory invariance of the standardized Quality-of-life Disease Impact Scale (QDIS(®)) in acute coronary syndrome patients: differential functioning of items and test.

PubMed

Deng, Nina; Anatchkova, Milena D; Waring, Molly E; Han, Kyung T; Ware, John E

2015-08-01

The Quality-of-life (QOL) Disease Impact Scale (QDIS(®)) standardizes the content and scoring of QOL impact attributed to different diseases using item response theory (IRT). This study examined the IRT invariance of the QDIS-standardized IRT parameters in an independent sample. The differential functioning of items and test (DFIT) of a static short-form (QDIS-7) was examined across two independent sources: patients hospitalized for acute coronary syndrome (ACS) in the TRACE-CORE study (N = 1,544) and chronically ill US adults in the QDIS standardization sample. "ACS-specific" IRT item parameters were calibrated and linearly transformed to compare to "standardized" IRT item parameters. Differences in IRT model-expected item, scale and theta scores were examined. The DFIT results were also compared in a standard logistic regression differential item functioning analysis. Item parameters estimated in the ACS sample showed lower discrimination parameters than the standardized discrimination parameters, but only small differences were found for thresholds parameters. In DFIT, results on the non-compensatory differential item functioning index (range 0.005-0.074) were all below the threshold of 0.096. Item differences were further canceled out at the scale level. IRT-based theta scores for ACS patients using standardized and ACS-specific item parameters were highly correlated (r = 0.995, root-mean-square difference = 0.09). Using standardized item parameters, ACS patients scored one-half standard deviation higher (indicating greater QOL impact) compared to chronically ill adults in the standardization sample. The study showed sufficient IRT invariance to warrant the use of standardized IRT scoring of QDIS-7 for studies comparing the QOL impact attributed to acute coronary disease and other chronic conditions.

Item Response Theory and Health Outcomes Measurement in the 21st Century

PubMed Central

Hays, Ron D.; Morales, Leo S.; Reise, Steve P.

2006-01-01

Item response theory (IRT) has a number of potential advantages over classical test theory in assessing self-reported health outcomes. IRT models yield invariant item and latent trait estimates (within a linear transformation), standard errors conditional on trait level, and trait estimates anchored to item content. IRT also facilitates evaluation of differential item functioning, inclusion of items with different response formats in the same scale, and assessment of person fit and is ideally suited for implementing computer adaptive testing. Finally, IRT methods can be helpful in developing better health outcome measures and in assessing change over time. These issues are reviewed, along with a discussion of some of the methodological and practical challenges in applying IRT methods. PMID:10982088

Investigating the Impact of Item Parameter Drift for Item Response Theory Models with Mixture Distributions.

PubMed

Park, Yoon Soo; Lee, Young-Sun; Xing, Kuan

2016-01-01

This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-world data. Twenty-one trended anchor items from the 1999, 2003, and 2007 administrations of Trends in International Mathematics and Science Study (TIMSS) were analyzed using unidimensional and mixture IRT models. TIMSS treats trended anchor items as invariant over testing administrations and uses pre-calibrated item parameters based on unidimensional IRT. However, empirical results showed evidence of two latent subgroups with IPD. Results also showed changes in the distribution of examinee ability between latent classes over the three administrations. A simulation study was conducted to examine the impact of IPD on the estimation of ability and item parameters, when data have underlying mixture distributions. Simulations used data generated from a mixture IRT model and estimated using unidimensional IRT. Results showed that data reflecting IPD using mixture IRT model led to IPD in the unidimensional IRT model. Changes in the distribution of examinee ability also affected item parameters. Moreover, drift with respect to item discrimination and distribution of examinee ability affected estimates of examinee ability. These findings demonstrate the need to caution and evaluate IPD using a mixture IRT framework to understand its effects on item parameters and examinee ability.

Investigating the Impact of Item Parameter Drift for Item Response Theory Models with Mixture Distributions

PubMed Central

Park, Yoon Soo; Lee, Young-Sun; Xing, Kuan

2016-01-01

This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-world data. Twenty-one trended anchor items from the 1999, 2003, and 2007 administrations of Trends in International Mathematics and Science Study (TIMSS) were analyzed using unidimensional and mixture IRT models. TIMSS treats trended anchor items as invariant over testing administrations and uses pre-calibrated item parameters based on unidimensional IRT. However, empirical results showed evidence of two latent subgroups with IPD. Results also showed changes in the distribution of examinee ability between latent classes over the three administrations. A simulation study was conducted to examine the impact of IPD on the estimation of ability and item parameters, when data have underlying mixture distributions. Simulations used data generated from a mixture IRT model and estimated using unidimensional IRT. Results showed that data reflecting IPD using mixture IRT model led to IPD in the unidimensional IRT model. Changes in the distribution of examinee ability also affected item parameters. Moreover, drift with respect to item discrimination and distribution of examinee ability affected estimates of examinee ability. These findings demonstrate the need to caution and evaluate IPD using a mixture IRT framework to understand its effects on item parameters and examinee ability. PMID:26941699

Equating with Miditests Using IRT

ERIC Educational Resources Information Center

Fitzpatrick, Joseph; Skorupski, William P.

2016-01-01

The equating performance of two internal anchor test structures--miditests and minitests--is studied for four IRT equating methods using simulated data. Originally proposed by Sinharay and Holland, miditests are anchors that have the same mean difficulty as the overall test but less variance in item difficulties. Four popular IRT equating methods…

Do Concept Inventories Actually Measure Anything?

ERIC Educational Resources Information Center

Wallace, Colin S.; Bailey, Janelle M.

2010-01-01

Although concept inventories are among the most frequently used tools in the physics and astronomy education communities, they are rarely evaluated using item response theory (IRT). When IRT models fit the data, they offer sample-independent estimates of item and person parameters. IRT may also provide a way to measure students' learning gains…

IRT Equating of the MCAT. MCAT Monograph.

ERIC Educational Resources Information Center

Hendrickson, Amy B.; Kolen, Michael J.

This study compared various equating models and procedures for a sample of data from the Medical College Admission Test(MCAT), considering how item response theory (IRT) equating results compare with classical equipercentile results and how the results based on use of various IRT models, observed score versus true score, direct versus linked…

Classification Consistency and Accuracy for Complex Assessments Using Item Response Theory

ERIC Educational Resources Information Center

Lee, Won-Chan

2010-01-01

In this article, procedures are described for estimating single-administration classification consistency and accuracy indices for complex assessments using item response theory (IRT). This IRT approach was applied to real test data comprising dichotomous and polytomous items. Several different IRT model combinations were considered. Comparisons…

Modern Psychometric Methodology: Applications of Item Response Theory

ERIC Educational Resources Information Center

Reid, Christine A.; Kolakowsky-Hayner, Stephanie A.; Lewis, Allen N.; Armstrong, Amy J.

2007-01-01

Item response theory (IRT) methodology is introduced as a tool for improving assessment instruments used with people who have disabilities. Need for this approach in rehabilitation is emphasized; differences between IRT and classical test theory are clarified. Concepts essential to understanding IRT are defined, necessary data assumptions are…

The Value of Item Response Theory in Clinical Assessment: A Review

ERIC Educational Resources Information Center

Thomas, Michael L.

2011-01-01

Item response theory (IRT) and related latent variable models represent modern psychometric theory, the successor to classical test theory in psychological assessment. Although IRT has become prevalent in the measurement of ability and achievement, its contributions to clinical domains have been less extensive. Applications of IRT to clinical…

Item response theory and the measurement of motor behavior.

PubMed

Safrit, M J; Cohen, A S; Costa, M G

1989-12-01

Item response theory (IRT) has been the focus of intense research and development activity in educational and psychological measurement during the past decade. Because this theory can provide more precise information about test items than other theories usually used in measuring motor behavior, the application of IRT in physical education and exercise science merits investigation. In IRT, the difficulty level of each item (e.g., trial or task) can be estimated and placed on the same scale as the ability of the examinee. Using this information, the test developer can determine the ability levels at which the test functions best. Equating the scores of individuals on two or more items or tests can be handled efficiently by applying IRT. The precision of the identification of performance standards in a mastery test context can be enhanced, as can adaptive testing procedures. In this tutorial, several potential benefits of applying IRT to the measurement of motor behavior were described. An example is provided using bowling data and applying the graded-response form of the Rasch IRT model. The data were calibrated and the goodness of fit was examined. This analysis is described in a step-by-step approach. Limitations to using an IRT model with a test consisting of repeated measures were noted.

Infrared thermography for condition monitoring - A review

NASA Astrophysics Data System (ADS)

Bagavathiappan, S.; Lahiri, B. B.; Saravanan, T.; Philip, John; Jayakumar, T.

2013-09-01

Temperature is one of the most common indicators of the structural health of equipment and components. Faulty machineries, corroded electrical connections, damaged material components, etc., can cause abnormal temperature distribution. By now, infrared thermography (IRT) has become a matured and widely accepted condition monitoring tool where the temperature is measured in real time in a non-contact manner. IRT enables early detection of equipment flaws and faulty industrial processes under operating condition thereby, reducing system down time, catastrophic breakdown and maintenance cost. Last three decades witnessed a steady growth in the use of IRT as a condition monitoring technique in civil structures, electrical installations, machineries and equipment, material deformation under various loading conditions, corrosion damages and welding processes. IRT has also found its application in nuclear, aerospace, food, paper, wood and plastic industries. With the advent of newer generations of infrared camera, IRT is becoming a more accurate, reliable and cost effective technique. This review focuses on the advances of IRT as a non-contact and non-invasive condition monitoring tool for machineries, equipment and processes. Various conditions monitoring applications are discussed in details, along with some basics of IRT, experimental procedures and data analysis techniques. Sufficient background information is also provided for the beginners and non-experts for easy understanding of the subject.

Effects of eight weeks of aerobic interval training and of isoinertial resistance training on risk factors of cardiometabolic diseases and exercise capacity in healthy elderly subjects

PubMed Central

Bruseghini, Paolo; Calabria, Elisa; Tam, Enrico; Milanese, Chiara; Oliboni, Eugenio; Pezzato, Andrea; Pogliaghi, Silvia; Salvagno, Gian Luca; Schena, Federico; Mucelli, Roberto Pozzi; Capelli, Carlo

2015-01-01

We investigated the effect of 8 weeks of high intensity interval training (HIT) and isoinertial resistance training (IRT) on cardiovascular fitness, muscle mass-strength and risk factors of metabolic syndrome in 12 healthy older adults (68 yy ± 4). HIT consisted in 7 two-minute repetitions at 80%–90% of V˙O2max, 3 times/w. After 4 months of recovery, subjects were treated with IRT, which included 4 sets of 7 maximal, bilateral knee extensions/flexions 3 times/w on a leg-press flywheel ergometer. HIT elicited significant: i) modifications of selected anthropometrical features; ii) improvements of cardiovascular fitness and; iii) decrease of systolic pressure. HIT and IRT induced hypertrophy of the quadriceps muscle, which, however, was paralleled by significant increases in strength only after IRT. Neither HIT nor IRT induced relevant changes in blood lipid profile, with the exception of a decrease of LDL and CHO after IRT. Physiological parameters related with aerobic fitness and selected body composition values predicting cardiovascular risk remained stable during detraining and, after IRT, they were complemented by substantial increase of muscle strength, leading to further improvements of quality of life of the subjects. PMID:26046575

Effects of instability versus traditional resistance training on strength, power and velocity in untrained men.

PubMed

Maté-Muñoz, José Luis; Monroy, Antonio J Antón; Jodra Jiménez, Pablo; Garnacho-Castaño, Manuel V

2014-09-01

The purpose of this study was compare the effects of a traditional and an instability resistance circuit training program on upper and lower limb strength, power, movement velocity and jumping ability. Thirty-six healthy untrained men were assigned to two experimental groups and a control group. Subjects in the experimental groups performed a resistance circuit training program consisting of traditional exercises (TRT, n = 10) or exercises executed in conditions of instability (using BOSU® and TRX®) (IRT, n = 12). Both programs involved three days per week of training for a total of seven weeks. The following variables were determined before and after training: maximal strength (1RM), average (AV) and peak velocity (PV), average (AP) and peak power (PP), all during bench press (BP) and back squat (BS) exercises, along with squat jump (SJ) height and counter movement jump (CMJ) height. All variables were found to significantly improve (p <0.05) in response to both training programs. Major improvements were observed in SJ height (IRT = 22.1%, TRT = 20.1%), CMJ height (IRT = 17.7%, TRT = 15.2%), 1RM in BS (IRT = 13.03%, TRT = 12.6%), 1RM in BP (IRT = 4.7%, TRT = 4.4%), AP in BS (IRT = 10.5%, TRT = 9.3%), AP in BP (IRT = 2.4%, TRT = 8.1%), PP in BS (IRT=19.42%, TRT = 22.3%), PP in BP (IRT = 7.6%, TRT = 11.5%), AV in BS (IRT = 10.5%, TRT = 9.4%), and PV in BS (IRT = 8.6%, TRT = 4.5%). Despite such improvements no significant differences were detected in the posttraining variables recorded for the two experimental groups. These data indicate that a circuit training program using two instability training devices is as effective in untrained men as a program executed under stable conditions for improving strength (1RM), power, movement velocity and jumping ability. Key PointsSimilar adaptations in terms of gains in strength, power, movement velocity and jumping ability were produced in response to both training programs.Both the stability and instability approaches seem suitable for healthy, physically-active individuals with or with limited experience in resistance training.RPE emerged as a useful tool to monitor exercise intensity during instability strength training.

Effects of Instability Versus Traditional Resistance Training on Strength, Power and Velocity in Untrained Men

PubMed Central

Maté-Muñoz, José Luis; Monroy, Antonio J. Antón; Jodra Jiménez, Pablo; Garnacho-Castaño, Manuel V.

2014-01-01

The purpose of this study was compare the effects of a traditional and an instability resistance circuit training program on upper and lower limb strength, power, movement velocity and jumping ability. Thirty-six healthy untrained men were assigned to two experimental groups and a control group. Subjects in the experimental groups performed a resistance circuit training program consisting of traditional exercises (TRT, n = 10) or exercises executed in conditions of instability (using BOSU® and TRX®) (IRT, n = 12). Both programs involved three days per week of training for a total of seven weeks. The following variables were determined before and after training: maximal strength (1RM), average (AV) and peak velocity (PV), average (AP) and peak power (PP), all during bench press (BP) and back squat (BS) exercises, along with squat jump (SJ) height and counter movement jump (CMJ) height. All variables were found to significantly improve (p <0.05) in response to both training programs. Major improvements were observed in SJ height (IRT = 22.1%, TRT = 20.1%), CMJ height (IRT = 17.7%, TRT = 15.2%), 1RM in BS (IRT = 13.03%, TRT = 12.6%), 1RM in BP (IRT = 4.7%, TRT = 4.4%), AP in BS (IRT = 10.5%, TRT = 9.3%), AP in BP (IRT = 2.4%, TRT = 8.1%), PP in BS (IRT=19.42%, TRT = 22.3%), PP in BP (IRT = 7.6%, TRT = 11.5%), AV in BS (IRT = 10.5%, TRT = 9.4%), and PV in BS (IRT = 8.6%, TRT = 4.5%). Despite such improvements no significant differences were detected in the posttraining variables recorded for the two experimental groups. These data indicate that a circuit training program using two instability training devices is as effective in untrained men as a program executed under stable conditions for improving strength (1RM), power, movement velocity and jumping ability. Key Points Similar adaptations in terms of gains in strength, power, movement velocity and jumping ability were produced in response to both training programs. Both the stability and instability approaches seem suitable for healthy, physically-active individuals with or with limited experience in resistance training. RPE emerged as a useful tool to monitor exercise intensity during instability strength training. PMID:25177170

VizieR Online Data Catalog: CaII H&K to CaII IRT echelle spectra (Montes+, 2000)

NASA Astrophysics Data System (ADS)

Montes, D.; Fernandez-Figueroa, M. J.; de Castro, E.; Cornide, M.; Latorre, A.; Sanz-Forcada, J.

2000-11-01

This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the CaII H&K to CaII IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted Hα profile of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component can be interpreted as arising from microflaring. Red-shifted absorption features in the Hα line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the EHα/EHβ ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn. The He I D3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He I D3, probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the CaII H&K lines of the giants 12 Cam, FG UMa and BM CVn. All the stars analysed show clear filled-in CaII IRT lines or even notable emission reversal. The small values of the E8542/E8498 ratio we have found indicate CaII IRT emission arises from plage-like regions. Orbital phase modulation of the chromospheric emission has been detected in some systems, in the case of HU Vir evidence of an active longitude area has been found. (5 data files).

Comparison of immunoreactive serum trypsinogen and lipase in Cystic Fibrosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lloyd-Still, J.D.; Weiss, S.; Wessel, H.

1984-01-01

The incidence of Cystic Fibrosis (CF) is 1 in 2,000. Early detection and treatment of CF may necessitate newborn screening with a reliable and cost-effective test. Serum immunoreactive trypsinogen (IRT) an enzyme produced by the pancreas, is detectable by radioimmunoassay (RIA) techniques. Recently, it has been shown that IRT is elevated in CF infants for the first few months of life and levels become subnormal as pancreatic insufficiency progresses. Other enzymes produced by the pancreas, such as lipase, are also elevated during this time. The author's earlier work confirmed previous reports of elevated IRT levels in CF infants. The developmentmore » of a new RIA for lipase (nuclipase) has enabled comparison of these 2 pancreatic enzymes in C.F. Serum IRT and lipase determinations were performed on 2 groups of CF patients; infants under 1 year of age, and children between 1 and 18 years of age. Control populations of the same age groups were included. The results showed that both trypsin (161 +- 92 ng/ml, range 20 to 400) and lipase (167 +- 151 ng/ml, range 29 to 500) are elevated in CF in the majority of infants. Control infants had values of IRT ranging from 20 to 29.5 ng/ml and lipase values ranging from 23 to 34 ng/ml. IRT becomes subnormal in most CF patients by 8 years of age as pancreatic function insufficiency increases. Lipase levels and IRT levels correlate well in infancy, but IRT is a more sensitive indicator of pancreatic insufficiency in older patients with CF.« less

An IRT Model with a Parameter-Driven Process for Change

ERIC Educational Resources Information Center

Rijmen, Frank; De Boeck, Paul; van der Maas, Han L. J.

2005-01-01

An IRT model with a parameter-driven process for change is proposed. Quantitative differences between persons are taken into account by a continuous latent variable, as in common IRT models. In addition, qualitative inter-individual differences and auto-dependencies are accounted for by assuming within-subject variability with respect to the…

Practical Issues in Estimating Classification Accuracy and Consistency with R Package cacIRT

ERIC Educational Resources Information Center

Lathrop, Quinn N.

2015-01-01

There are two main lines of research in estimating classification accuracy (CA) and classification consistency (CC) under Item Response Theory (IRT). The R package cacIRT provides computer implementations of both approaches in an accessible and unified framework. Even with available implementations, there remains decisions a researcher faces when…

IRT-Stimulus Contingencies in Chained Schedules: Implications for the Concept of Conditioned Reinforcement

ERIC Educational Resources Information Center

Bejarano, Rafael; Hackenberg, Timothy D.

2007-01-01

Two experiments with pigeons investigated the effects of contingencies between interresponse times (IRTs) and the transitions between the components of 2- and 4-component chained schedules (Experiments 1 and 2, respectively). The probability of component transitions varied directly with the most recent (Lag 0) IRT in some experimental conditions…

Item Response Theory with Estimation of the Latent Density Using Davidian Curves

ERIC Educational Resources Information Center

Woods, Carol M.; Lin, Nan

2009-01-01

Davidian-curve item response theory (DC-IRT) is introduced, evaluated with simulations, and illustrated using data from the Schedule for Nonadaptive and Adaptive Personality Entitlement scale. DC-IRT is a method for fitting unidimensional IRT models with maximum marginal likelihood estimation, in which the latent density is estimated,…

An Introduction to Item Response Theory for Health Behavior Researchers

ERIC Educational Resources Information Center

Warne, Russell T.; McKyer, E. J. Lisako; Smith, Matthew L.

2012-01-01

Objective: To introduce item response theory (IRT) to health behavior researchers by contrasting it with classical test theory and providing an example of IRT in health behavior. Method: Demonstrate IRT by fitting the 2PL model to substance-use survey data from the Adolescent Health Risk Behavior questionnaire (n = 1343 adolescents). Results: An…

Item Response Theory: A Basic Concept

ERIC Educational Resources Information Center

Mahmud, Jumailiyah

2017-01-01

With the development in computing technology, item response theory (IRT) develops rapidly, and has become a user friendly application in psychometrics world. Limitation in classical theory is one aspect that encourages the use of IRT. In this study, the basic concept of IRT will be discussed. In addition, it will briefly review the ability…

The Utility of IRT in Small-Sample Testing Applications.

ERIC Educational Resources Information Center

Sireci, Stephen G.

The utility of modified item response theory (IRT) models in small sample testing applications was studied. The modified IRT models were modifications of the one- and two-parameter logistic models. One-, two-, and three-parameter models were also studied. Test data were from 4 years of a national certification examination for persons desiring…

A Bayesian Beta-Mixture Model for Nonparametric IRT (BBM-IRT)

ERIC Educational Resources Information Center

Arenson, Ethan A.; Karabatsos, George

2017-01-01

Item response models typically assume that the item characteristic (step) curves follow a logistic or normal cumulative distribution function, which are strictly monotone functions of person test ability. Such assumptions can be overly-restrictive for real item response data. We propose a simple and more flexible Bayesian nonparametric IRT model…

IRTPRO 2.1 for Windows (Item Response Theory for Patient-Reported Outcomes)

ERIC Educational Resources Information Center

Paek, Insu; Han, Kyung T.

2013-01-01

This article reviews a new item response theory (IRT) model estimation program, IRTPRO 2.1, for Windows that is capable of unidimensional and multidimensional IRT model estimation for existing and user-specified constrained IRT models for dichotomously and polytomously scored item response data. (Contains 1 figure and 2 notes.)

Item Response Theory: Overview, Applications, and Promise for Institutional Research

ERIC Educational Resources Information Center

Bowman, Nicholas A.; Herzog, Serge; Sharkness, Jessica

2014-01-01

Item Response Theory (IRT) is a measurement theory that is ideal for scale and test development in institutional research, but it is not without its drawbacks. This chapter provides an overview of IRT, describes an example of its use, and highlights the pros and cons of using IRT in applied settings.

Building an Evaluation Scale using Item Response Theory.

PubMed

Lalor, John P; Wu, Hao; Yu, Hong

2016-11-01

Evaluation of NLP methods requires testing against a previously vetted gold-standard test set and reporting standard metrics (accuracy/precision/recall/F1). The current assumption is that all items in a given test set are equal with regards to difficulty and discriminating power. We propose Item Response Theory (IRT) from psychometrics as an alternative means for gold-standard test-set generation and NLP system evaluation. IRT is able to describe characteristics of individual items - their difficulty and discriminating power - and can account for these characteristics in its estimation of human intelligence or ability for an NLP task. In this paper, we demonstrate IRT by generating a gold-standard test set for Recognizing Textual Entailment. By collecting a large number of human responses and fitting our IRT model, we show that our IRT model compares NLP systems with the performance in a human population and is able to provide more insight into system performance than standard evaluation metrics. We show that a high accuracy score does not always imply a high IRT score, which depends on the item characteristics and the response pattern.

Building an Evaluation Scale using Item Response Theory

PubMed Central

Lalor, John P.; Wu, Hao; Yu, Hong

2016-01-01

Evaluation of NLP methods requires testing against a previously vetted gold-standard test set and reporting standard metrics (accuracy/precision/recall/F1). The current assumption is that all items in a given test set are equal with regards to difficulty and discriminating power. We propose Item Response Theory (IRT) from psychometrics as an alternative means for gold-standard test-set generation and NLP system evaluation. IRT is able to describe characteristics of individual items - their difficulty and discriminating power - and can account for these characteristics in its estimation of human intelligence or ability for an NLP task. In this paper, we demonstrate IRT by generating a gold-standard test set for Recognizing Textual Entailment. By collecting a large number of human responses and fitting our IRT model, we show that our IRT model compares NLP systems with the performance in a human population and is able to provide more insight into system performance than standard evaluation metrics. We show that a high accuracy score does not always imply a high IRT score, which depends on the item characteristics and the response pattern.1 PMID:28004039

Analysis test of understanding of vectors with the three-parameter logistic model of item response theory and item response curves technique

NASA Astrophysics Data System (ADS)

Rakkapao, Suttida; Prasitpong, Singha; Arayathanitkul, Kwan

2016-12-01

This study investigated the multiple-choice test of understanding of vectors (TUV), by applying item response theory (IRT). The difficulty, discriminatory, and guessing parameters of the TUV items were fit with the three-parameter logistic model of IRT, using the parscale program. The TUV ability is an ability parameter, here estimated assuming unidimensionality and local independence. Moreover, all distractors of the TUV were analyzed from item response curves (IRC) that represent simplified IRT. Data were gathered on 2392 science and engineering freshmen, from three universities in Thailand. The results revealed IRT analysis to be useful in assessing the test since its item parameters are independent of the ability parameters. The IRT framework reveals item-level information, and indicates appropriate ability ranges for the test. Moreover, the IRC analysis can be used to assess the effectiveness of the test's distractors. Both IRT and IRC approaches reveal test characteristics beyond those revealed by the classical analysis methods of tests. Test developers can apply these methods to diagnose and evaluate the features of items at various ability levels of test takers.

A Multilevel Testlet Model for Dual Local Dependence

ERIC Educational Resources Information Center

Jiao, Hong; Kamata, Akihito; Wang, Shudong; Jin, Ying

2012-01-01

The applications of item response theory (IRT) models assume local item independence and that examinees are independent of each other. When a representative sample for psychometric analysis is selected using a cluster sampling method in a testlet-based assessment, both local item dependence and local person dependence are likely to be induced.…

Chromospheric activity on the late-type star V1355 Ori using Lijiang 1.8-m and 2.4-m telescopes

NASA Astrophysics Data System (ADS)

Pi, Qing-Feng; Zhang, Li-Yun; Chang, Liang; Han, Xian-Ming; Lu, Hong-Peng; Zhang, Xi-Liang; Wang, Dai-Mei

2016-10-01

We obtained new high-resolution spectra using the Lijiang 1.8-m and 2.4-m telescopes to investigate the chromospheric activities of V1355 Ori as indicated in the behaviors of Ca ii H&K, Hδ, Hγ, Hβ, Na i D1, D2, Hα and Ca ii infrared triplet (IRT) lines. The observed spectra show obvious emissions above the continuum in Ca ii H&K lines, absorptions in the Hδ, Hγ, Hβ and Na i D1, D2 lines, variable behavior (filled-in absorption, partial emission with a core absorption component or emission above the continuum) in the Hα line, and weak self-reversal emissions in the strong filled-in absorptions of the Ca ii IRT lines. We used a spectral subtraction technique to analyze our data. The results show no excess emission in the Hδ and Hγ lines, very weak excess emissions in the Na i D1, D2 lines, excess emission in the Hβ line, clear excess emission in the Hα line, and excess emissions in the Ca ii IRT lines. The value of the ratio of EW8542/EW8498 is in the range 0.9 to 1.7, which implies that chromospheric activity might have been caused by plage events. The value of the ratio E Hα/E Hβ is above 3, indicating that the Balmer lines would arise from prominence-like material. We also found time variations in light curves associated with equivalent widths of chromospheric activity lines in the Na i D1, D2, Ca ii IRT and Hα lines in particular. These phenomena can be explained by plage events, which are consistent with the behavior of chromospheric activity indicators.

Multi-modality image registration for effective thermographic fever screening

NASA Astrophysics Data System (ADS)

Dwith, C. Y. N.; Ghassemi, Pejhman; Pfefer, Joshua; Casamento, Jon; Wang, Quanzeng

2017-02-01

Fever screening based on infrared thermographs (IRTs) is a viable mass screening approach during infectious disease pandemics, such as Ebola and Severe Acute Respiratory Syndrome (SARS), for temperature monitoring in public places like hospitals and airports. IRTs have been found to be powerful, quick and non-invasive methods for detecting elevated temperatures. Moreover, regions medially adjacent to the inner canthi (called the canthi regions in this paper) are preferred sites for fever screening. Accurate localization of the canthi regions can be achieved through multi-modality registration of infrared (IR) and white-light images. Here we propose a registration method through a coarse-fine registration strategy using different registration models based on landmarks and edge detection on eye contours. We have evaluated the registration accuracy to be within +/- 2.7 mm, which enables accurate localization of the canthi regions.

Diagnosing cystic fibrosis in newborn screening in Poland - 15 years of experience.

PubMed

Sands, Dorota; Zybert, Katarzyna; Mierzejewska, Ewa; Ołtarzewski, Mariusz

2015-01-01

Early diagnosis of cystic fibrosis (CF) made by the introduction of CF NBS (Cystic Fibrosis Newborn Screening) provides the opportunity to undertake preventive measures and provide treatment before the development of irreversible changes in the respiratory tract and other complications. CF NBS was conducted as a pilot programme in four Polish districts in the period 1999-2003. In 2006 CF NBS started again and was gradually extended across the country. The aim of this study was to show the evolution of the Polish CF NBS strategies and assess the diagnostic consequences of this programme. The study involved children diagnosed and treated only in the IMiD Centre. The strategy in Polish CF NBS was modified over time. Firstly, the model IRT/IRT and IRT/IRT/DNA with one mutation was implemented, which was followed by IRT/DNA with a gradually expanding number of CFTR mutations (tab. I). Newborns with positive results of CF NBS were called to the CF IMiD Centre, and sweat tests were performed. The children diagnosed and children with mutations in both alleles of the CFTR gene even if at least one of them had undefined pathogenicity) were taken under IMiD Centre care. Sensitivity, specificity and positive predictive values during subsequent stages of CF NBS were calculated (tab. III). During the 1999-2003 pilot study 444 063 newborns underwent CF NBS and in 74 cases CF was diagnosed. 582 693 newborns were screened from September 2006 to December 2011 in four regions and 100 children were diagnosed with CF. The frequencies of CF in the Polish population in both screening periods were 1:5767 and 1:5712 respectively. Firstly, the IRT/IRT model was implemented, but the number of newborns called to the CF Centre was high - the PPV was 7.6%. In the next step CF NBS DNA analysis was used. Here sensitivity and specificity were high - nearly 100%. In the following years the number of mutations detected was expanded (including 16 most common ones in the Polish population). Due to the panel changes, the number of calls declined and the PPV (predictive positive value) improved (to 26.1%) after the application of expanded genetic analysis. Expanding the panel of mutations resulted in an increased number of carriers and observational subjects. IRT/DNA strategy with expanded DNA analysis provides the opportunity for earlier CF diagnosis even in children with normal sweat test values. However, this model caused frequent carrier detection and inconclusive diagnosis in comparison to IRT/IRT or IRT/IRT/DNA with a limited number of mutations. Further research and changes in Polish CF NBS are needed to increase the PPV, while preserving high sensitivity and specificity..

Non-ignorable missingness item response theory models for choice effects in examinee-selected items.

PubMed

Liu, Chen-Wei; Wang, Wen-Chung

2017-11-01

Examinee-selected item (ESI) design, in which examinees are required to respond to a fixed number of items in a given set, always yields incomplete data (i.e., when only the selected items are answered, data are missing for the others) that are likely non-ignorable in likelihood inference. Standard item response theory (IRT) models become infeasible when ESI data are missing not at random (MNAR). To solve this problem, the authors propose a two-dimensional IRT model that posits one unidimensional IRT model for observed data and another for nominal selection patterns. The two latent variables are assumed to follow a bivariate normal distribution. In this study, the mirt freeware package was adopted to estimate parameters. The authors conduct an experiment to demonstrate that ESI data are often non-ignorable and to determine how to apply the new model to the data collected. Two follow-up simulation studies are conducted to assess the parameter recovery of the new model and the consequences for parameter estimation of ignoring MNAR data. The results of the two simulation studies indicate good parameter recovery of the new model and poor parameter recovery when non-ignorable missing data were mistakenly treated as ignorable. © 2017 The British Psychological Society.

Examining Differential Item Functioning: IRT-Based Detection in the Framework of Confirmatory Factor Analysis

ERIC Educational Resources Information Center

Dimitrov, Dimiter M.

2017-01-01

This article offers an approach to examining differential item functioning (DIF) under its item response theory (IRT) treatment in the framework of confirmatory factor analysis (CFA). The approach is based on integrating IRT- and CFA-based testing of DIF and using bias-corrected bootstrap confidence intervals with a syntax code in Mplus.

Investigation of IRT-Based Equating Methods in the Presence of Outlier Common Items

ERIC Educational Resources Information Center

Hu, Huiqin; Rogers, W. Todd; Vukmirovic, Zarko

2008-01-01

Common items with inconsistent b-parameter estimates may have a serious impact on item response theory (IRT)--based equating results. To find a better way to deal with the outlier common items with inconsistent b-parameters, the current study investigated the comparability of 10 variations of four IRT-based equating methods (i.e., concurrent…

Stability of Rasch Scales over Time

ERIC Educational Resources Information Center

Taylor, Catherine S.; Lee, Yoonsun

2010-01-01

Item response theory (IRT) methods are generally used to create score scales for large-scale tests. Research has shown that IRT scales are stable across groups and over time. Most studies have focused on items that are dichotomously scored. Now Rasch and other IRT models are used to create scales for tests that include polytomously scored items.…

The Relationship between CTT and IRT Approaches in Analyzing Item Characteristics

ERIC Educational Resources Information Center

Abedalaziz, Nabeel; Leng, Chin Hai

2013-01-01

Most of the tests and inventories used by counseling psychologists have been developed using CTT; IRT derives from what is called latent trait theory. A number of important differences exist between CTT- versus IRT-based approaches to both test development and evaluation, as well as the process of scoring the response profiles of individual…

Score Equating and Item Response Theory: Some Practical Considerations.

ERIC Educational Resources Information Center

Cook, Linda L.; Eignor, Daniel R.

The purposes of this paper are five-fold to discuss: (1) when item response theory (IRT) equating methods should provide better results than traditional methods; (2) which IRT model, the three-parameter logistic or the one-parameter logistic (Rasch), is the most reasonable to use; (3) what unique contributions IRT methods can offer the equating…

Using the Item Response Theory (IRT) for Educational Evaluation through Games

ERIC Educational Resources Information Center

Euzébio Batista, Marcelo Henrique; Victória Barbosa, Jorge Luis; da Rosa Tavares, João Elison; Hackenhaar, Jonathan Luis

2013-01-01

This article shows the application of Item Response Theory (IRT) for educational evaluation using games. The article proposes a computational model to create user profiles, called Psychometric Profile Generator (PPG). PPG uses the IRT mathematical model for exploring the levels of skills and behaviors in the form of items and/or stimuli. The model…

Technology and Teaching: Promoting Active Learning Using Individual Response Technology in Large Introductory Psychology Classes

ERIC Educational Resources Information Center

Poirier, Christopher R.; Feldman, Robert S.

2007-01-01

Individual response technology (IRT), in which students use wireless handsets to communicate real-time responses, permits the recording and display of aggregated student responses during class. In comparison to a traditional class that did not employ IRT, students using IRT performed better on exams and held positive attitudes toward the…

Using IRT Trait Estimates versus Summated Scores in Predicting Outcomes

ERIC Educational Resources Information Center

Xu, Ting; Stone, Clement A.

2012-01-01

It has been argued that item response theory trait estimates should be used in analyses rather than number right (NR) or summated scale (SS) scores. Thissen and Orlando postulated that IRT scaling tends to produce trait estimates that are linearly related to the underlying trait being measured. Therefore, IRT trait estimates can be more useful…

An Investigation of Item Fit Statistics for Mixed IRT Models

ERIC Educational Resources Information Center

Chon, Kyong Hee

2009-01-01

The purpose of this study was to investigate procedures for assessing model fit of IRT models for mixed format data. In this study, various IRT model combinations were fitted to data containing both dichotomous and polytomous item responses, and the suitability of the chosen model mixtures was evaluated based on a number of model fit procedures.…

Measurement Invariance in Careers Research: Using IRT to Study Gender Differences in Medical Students' Specialization Decisions

ERIC Educational Resources Information Center

Behrend, Tara S.; Thompson, Lori Foster; Meade, Adam W.; Newton, Dale A.; Grayson, Martha S.

2008-01-01

The current study demonstrates the use of item response theory (IRT) to conduct measurement invariance analyses in careers research. A self-report survey was used to assess the importance 1,363 fourth-year medical students placed on opportunities to provide comprehensive patient care when choosing a career specialty. IRT analyses supported…

Some Observations on the Identification and Interpretation of the 3PL IRT Model

ERIC Educational Resources Information Center

Azevedo, Caio Lucidius Naberezny

2009-01-01

The paper by Maris, G., & Bechger, T. (2009) entitled, "On the Interpreting the Model Parameters for the Three Parameter Logistic Model," addressed two important questions concerning the three parameter logistic (3PL) item response theory (IRT) model (and in a broader sense, concerning all IRT models). The first one is related to the model…

An Introduction to Item Response Theory and Rasch Models for Speech-Language Pathologists

ERIC Educational Resources Information Center

Baylor, Carolyn; Hula, William; Donovan, Neila J.; Doyle, Patrick J.; Kendall, Diane; Yorkston, Kathryn

2011-01-01

Purpose: To present a primarily conceptual introduction to item response theory (IRT) and Rasch models for speech-language pathologists (SLPs). Method: This tutorial introduces SLPs to basic concepts and terminology related to IRT as well as the most common IRT models. The article then continues with an overview of how instruments are developed…

Stellar rotation periods determined from simultaneously measured Ca II H&K and Ca II IRT lines

NASA Astrophysics Data System (ADS)

Mittag, M.; Hempelmann, A.; Schmitt, J. H. M. M.; Fuhrmeister, B.; González-Pérez, J. N.; Schröder, K.-P.

2017-11-01

Aims: Previous studies have shown that, for late-type stars, activity indicators derived from the Ca II infrared-triplet (IRT) lines are correlated with the indicators derived from the Ca II H&K lines. Therefore, the Ca II IRT lines are in principle usable for activity studies, but they may be less sensitive when measuring the rotation period. Our goal is to determine whether the Ca II IRT lines are sufficiently sensitive to measure rotation periods and how any Ca II IRT derived rotation periods compare with periods derived from the "classical" Mount Wilson S-index. Methods: To analyse the Ca II IRT lines' sensitivity and to measure rotation periods, we define an activity index for each of the Ca II IRT lines similar to the Mount Wilson S-index and perform a period analysis for the lines separately and jointly. Results: For eleven late-type stars we can measure the rotation periods using the Ca II IRT indices similar to those found in the Mount Wilson S-index time series and find that a period derived from all four indices gives the most probable rotation period; we find good agreement for stars with already existing literature values. In a few cases the computed periodograms show a complicated structure with multiple peaks, meaning that formally different periods are derived in different indices. We show that in one case, this is due to data sampling effects and argue that denser cadence sampling is necessary to provide credible evidence for differential rotation. However, our TIGRE data for HD 101501 shows good evidence for the presence of differential rotation.

Prophylactic Effect of Probiotics on the Development of Experimental Autoimmune Myasthenia Gravis

PubMed Central

Chae, Chang-Suk; Kwon, Ho-Keun; Hwang, Ji-Sun; Kim, Jung-Eun; Im, Sin-Hyeog

2012-01-01

Probiotics are live bacteria that confer health benefits to the host physiology. Although protective role of probiotics have been reported in diverse diseases, no information is available whether probiotics can modulate neuromuscular immune disorders. We have recently demonstrated that IRT5 probiotics, a mixture of 5 probiotics, could suppress diverse experimental disorders in mice model. In this study we further investigated whether IRT5 probiotics could modulate the progression of experimental autoimmune myasthenia gravis (EAMG). Myasthenia gravis (MG) is a T cell dependent antibody mediated autoimmune disorder in which acetylcholine receptor (AChR) at the neuromuscular junction is the major auto-antigen. Oral administration of IRT5 probiotics significantly reduced clinical symptoms of EAMG such as weight loss, body trembling and grip strength. Prophylactic effect of IRT5 probiotics on EMAG is mediated by down-regulation of effector function of AChR-reactive T cells and B cells. Administration of IRT5 probiotics decreased AChR-reactive lymphocyte proliferation, anti-AChR reactive IgG levels and inflammatory cytokine levels such as IFN-γ, TNF-α, IL-6 and IL-17. Down-regulation of inflammatory mediators in AChR-reactive lymphocytes by IRT5 probiotics is mediated by the generation of regulatory dendritic cells (rDCs) that express increased levels of IL-10, TGF-β, arginase 1 and aldh1a2. Furthermore, DCs isolated from IRT5 probiotics-fed group effectively converted CD4+ T cells into CD4+Foxp3+ regulatory T cells compared with control DCs. Our data suggest that IRT5 probiotics could be applicable to modulate antibody mediated autoimmune diseases including myasthenia gravis. PMID:23284891

Item Response Theory as an Efficient Tool to Describe a Heterogeneous Clinical Rating Scale in De Novo Idiopathic Parkinson's Disease Patients.

PubMed

Buatois, Simon; Retout, Sylvie; Frey, Nicolas; Ueckert, Sebastian

2017-10-01

This manuscript aims to precisely describe the natural disease progression of Parkinson's disease (PD) patients and evaluate approaches to increase the drug effect detection power. An item response theory (IRT) longitudinal model was built to describe the natural disease progression of 423 de novo PD patients followed during 48 months while taking into account the heterogeneous nature of the MDS-UPDRS. Clinical trial simulations were then used to compare drug effect detection power from IRT and sum of item scores based analysis under different analysis endpoints and drug effects. The IRT longitudinal model accurately describes the evolution of patients with and without PD medications while estimating different progression rates for the subscales. When comparing analysis methods, the IRT-based one consistently provided the highest power. IRT is a powerful tool which enables to capture the heterogeneous nature of the MDS-UPDRS.

The value of item response theory in clinical assessment: a review.

PubMed

Thomas, Michael L

2011-09-01

Item response theory (IRT) and related latent variable models represent modern psychometric theory, the successor to classical test theory in psychological assessment. Although IRT has become prevalent in the measurement of ability and achievement, its contributions to clinical domains have been less extensive. Applications of IRT to clinical assessment are reviewed to appraise its current and potential value. Benefits of IRT include comprehensive analyses and reduction of measurement error, creation of computer adaptive tests, meaningful scaling of latent variables, objective calibration and equating, evaluation of test and item bias, greater accuracy in the assessment of change due to therapeutic intervention, and evaluation of model and person fit. The theory may soon reinvent the manner in which tests are selected, developed, and scored. Although challenges remain to the widespread implementation of IRT, its application to clinical assessment holds great promise. Recommendations for research, test development, and clinical practice are provided.

Application of an IRT Polytomous Model for Measuring Health Related Quality of Life

ERIC Educational Resources Information Center

Tejada, Antonio J. Rojas; Rojas, Oscar M. Lozano

2005-01-01

Background: The Item Response Theory (IRT) has advantages for measuring Health Related Quality of Life (HRQOL) as opposed to the Classical Tests Theory (CTT). Objectives: To present the results of the application of a polytomous model based on IRT, specifically, the Rating Scale Model (RSM), to measure HRQOL with the EORTC QLQ-C30. Methods: 103…

Detection of Differential Item Functioning with Nonlinear Regression: A Non-IRT Approach Accounting for Guessing

ERIC Educational Resources Information Center

Drabinová, Adéla; Martinková, Patrícia

2017-01-01

In this article we present a general approach not relying on item response theory models (non-IRT) to detect differential item functioning (DIF) in dichotomous items with presence of guessing. The proposed nonlinear regression (NLR) procedure for DIF detection is an extension of method based on logistic regression. As a non-IRT approach, NLR can…

Application of the IRT and TRT Models to a Reading Comprehension Test

ERIC Educational Resources Information Center

Kim, Weon H.

2017-01-01

The purpose of the present study is to apply the item response theory (IRT) and testlet response theory (TRT) models to a reading comprehension test. This study applied the TRT models and the traditional IRT model to a seventh-grade reading comprehension test (n = 8,815) with eight testlets. These three models were compared to determine the best…

Consequences of Ignoring Guessing when Estimating the Latent Density in Item Response Theory

ERIC Educational Resources Information Center

Woods, Carol M.

2008-01-01

In Ramsay-curve item response theory (RC-IRT), the latent variable distribution is estimated simultaneously with the item parameters. In extant Monte Carlo evaluations of RC-IRT, the item response function (IRF) used to fit the data is the same one used to generate the data. The present simulation study examines RC-IRT when the IRF is imperfectly…

Relationships among Classical Test Theory and Item Response Theory Frameworks via Factor Analytic Models

ERIC Educational Resources Information Center

Kohli, Nidhi; Koran, Jennifer; Henn, Lisa

2015-01-01

There are well-defined theoretical differences between the classical test theory (CTT) and item response theory (IRT) frameworks. It is understood that in the CTT framework, person and item statistics are test- and sample-dependent. This is not the perception with IRT. For this reason, the IRT framework is considered to be theoretically superior…

Standard Errors and Confidence Intervals from Bootstrapping for Ramsay-Curve Item Response Theory Model Item Parameters

ERIC Educational Resources Information Center

Gu, Fei; Skorupski, William P.; Hoyle, Larry; Kingston, Neal M.

2011-01-01

Ramsay-curve item response theory (RC-IRT) is a nonparametric procedure that estimates the latent trait using splines, and no distributional assumption about the latent trait is required. For item parameters of the two-parameter logistic (2-PL), three-parameter logistic (3-PL), and polytomous IRT models, RC-IRT can provide more accurate estimates…

Time change of perceptual reversal of ambiguous figures by rTMS.

PubMed

Nojima, K; Ge, S; Katayama, Y; Iramina, K

2010-01-01

The aim of this study was to investigate the effect of stimulus frequency and number of pulses during rTMS (repetitive transcranial magnetic stimulation) on the phenomenon of perceptual reversal. Particularly, we focused on the temporal dynamics of perceptual reversal in the right SPL (superior parietal lobule), using the spinning wheel illusion. We measured the IRT (inter-reversal time) of perceptual reversal. To investigate whether stimulus frequency or the number of pulses is critical for the rTMS effect, we applied the following schedules over the right SPL and the right PTL (posterior temporal lobe): 0.25Hz 60 pulses, 0.25Hz 120pulses, 0.5Hz 120 pulses, and 1Hz 120 pulses biphasic rTMS at 90% of the resting motor threshold. As a control, we included a No-TMS condition. The results showed that rTMS with 0.25Hz 60 pulses over the right SPL caused shorter IRT. There were no significant differences between IRTs for rTMS with 0.25Hz 120 pulses, 0.5Hz 120 pulses or 1Hz 120 pulses over the right SPL. Comparing these results with those of a previous study, we found that an rTMS condition with 60 pulses causes shorter IRT; 240 pulses causes longer IRT; and 120 pulses does not change IRT. Therefore, when applying rTMS over the right SPL, the IRT of perceptual reversal is primarily affected by the number of pulses.

Fitting IRT Models to Dichotomous and Polytomous Data: Assessing the Relative Model-Data Fit of Ideal Point and Dominance Models

ERIC Educational Resources Information Center

Tay, Louis; Ali, Usama S.; Drasgow, Fritz; Williams, Bruce

2011-01-01

This study investigated the relative model-data fit of an ideal point item response theory (IRT) model (the generalized graded unfolding model [GGUM]) and dominance IRT models (e.g., the two-parameter logistic model [2PLM] and Samejima's graded response model [GRM]) to simulated dichotomous and polytomous data generated from each of these models.…

The Estimation of the IRT Reliability Coefficient and Its Lower and Upper Bounds, with Comparisons to CTT Reliability Statistics

ERIC Educational Resources Information Center

Kim, Seonghoon; Feldt, Leonard S.

2010-01-01

The primary purpose of this study is to investigate the mathematical characteristics of the test reliability coefficient rho[subscript XX'] as a function of item response theory (IRT) parameters and present the lower and upper bounds of the coefficient. Another purpose is to examine relative performances of the IRT reliability statistics and two…

The Reliability and Precision of Total Scores and IRT Estimates as a Function of Polytomous IRT Parameters and Latent Trait Distribution

ERIC Educational Resources Information Center

Culpepper, Steven Andrew

2013-01-01

A classic topic in the fields of psychometrics and measurement has been the impact of the number of scale categories on test score reliability. This study builds on previous research by further articulating the relationship between item response theory (IRT) and classical test theory (CTT). Equations are presented for comparing the reliability and…

A Nonparametric Approach for Assessing Goodness-of-Fit of IRT Models in a Mixed Format Test

ERIC Educational Resources Information Center

Liang, Tie; Wells, Craig S.

2015-01-01

Investigating the fit of a parametric model plays a vital role in validating an item response theory (IRT) model. An area that has received little attention is the assessment of multiple IRT models used in a mixed-format test. The present study extends the nonparametric approach, proposed by Douglas and Cohen (2001), to assess model fit of three…

A Combined IRT and SEM Approach for Individual-Level Assessment in Test-Retest Studies

ERIC Educational Resources Information Center

Ferrando, Pere J.

2015-01-01

The standard two-wave multiple-indicator model (2WMIM) commonly used to analyze test-retest data provides information at both the group and item level. Furthermore, when applied to binary and graded item responses, it is related to well-known item response theory (IRT) models. In this article the IRT-2WMIM relations are used to obtain additional…

Performance of the Generalized S-X[Superscript 2] Item Fit Index for Polytomous IRT Models

ERIC Educational Resources Information Center

Kang, Taehoon; Chen, Troy T.

2008-01-01

Orlando and Thissen's S-X[superscript 2] item fit index has performed better than traditional item fit statistics such as Yen' s Q[subscript 1] and McKinley and Mill' s G[superscript 2] for dichotomous item response theory (IRT) models. This study extends the utility of S-X[superscript 2] to polytomous IRT models, including the generalized partial…

Comparing five depression measures in depressed Chinese patients using item response theory: an examination of item properties, measurement precision and score comparability.

PubMed

Zhao, Yue; Chan, Wai; Lo, Barbara Chuen Yee

2017-04-04

Item response theory (IRT) has been increasingly applied to patient-reported outcome (PRO) measures. The purpose of this study is to apply IRT to examine item properties (discrimination and severity of depressive symptoms), measurement precision and score comparability across five depression measures, which is the first study of its kind in the Chinese context. A clinical sample of 207 Hong Kong Chinese outpatients was recruited. Data analyses were performed including classical item analysis, IRT concurrent calibration and IRT true score equating. The IRT assumptions of unidimensionality and local independence were tested respectively using confirmatory factor analysis and chi-square statistics. The IRT linking assumptions of construct similarity, equity and subgroup invariance were also tested. The graded response model was applied to concurrently calibrate all five depression measures in a single IRT run, resulting in the item parameter estimates of these measures being placed onto a single common metric. IRT true score equating was implemented to perform the outcome score linking and construct score concordances so as to link scores from one measure to corresponding scores on another measure for direct comparability. Findings suggested that (a) symptoms on depressed mood, suicidality and feeling of worthlessness served as the strongest discriminating indicators, and symptoms concerning suicidality, changes in appetite, depressed mood, feeling of worthlessness and psychomotor agitation or retardation reflected high levels of severity in the clinical sample. (b) The five depression measures contributed to various degrees of measurement precision at varied levels of depression. (c) After outcome score linking was performed across the five measures, the cut-off scores led to either consistent or discrepant diagnoses for depression. The study provides additional evidence regarding the psychometric properties and clinical utility of the five depression measures, offers methodological contributions to the appropriate use of IRT in PRO measures, and helps elucidate cultural variation in depressive symptomatology. The approach of concurrently calibrating and linking multiple PRO measures can be applied to the assessment of PROs other than the depression context.

Screening for fever by remote-sensing infrared thermographic camera.

PubMed

Chan, Lung-Sang; Cheung, Giselle T Y; Lauder, Ian J; Kumana, Cyrus R; Lauder, Ian J

2004-01-01

Following the severe acute respiratory syndrome (SARS) outbreak, remote-sensing infrared thermography (IRT) has been advocated as a possible means of screening for fever in travelers at airports and border crossings, but its applicability has not been established. We therefore set out to evaluate (1) the feasibility of IRT imaging to identify subjects with fever, and (2) the optimal instrumental configuration and validity for such testing. Over a 20-day inclusive period, 176 subjects (49 hospital inpatients without SARS or suspected SARS, 99 health clinic attendees and 28 healthy volunteers) were recruited. Remotely sensed IRT readings were obtained from various parts of the front and side of the face (at distances of 1.5 and 0.5 m), and compared to concurrently determined body temperature measurements using conventional means (aural tympanic IRT and oral mercury thermometry). The resulting data were submitted to linear regression/correlation and sensitivity analyses. All recruits gave prior informed consent and our Faculty Institutional Review Board approved the protocol. Optimal correlations were found between conventionally measured body temperatures and IRT readings from (1) the front of the face at 1.5m with the mouth open (r=0.80), (2) the ear at 0.5 m (r=0.79), and (3) the side of the face at 1.5m (r=0.76). Average IRT readings from the forehead and elsewhere were 1 degrees C to 2 degrees C lower and correlated less well. Ear IRT readings at 0.5 m yielded the narrowest confidence intervals and could be used to predict conventional body temperature readings of < or = 38 degrees C with a sensitivity and specificity of 83% and 88% respectively. IRT readings from the side of the face, especially from the ear at 0.5 m, yielded the most reliable, precise and consistent estimates of conventionally determined body temperatures. Our results have important implications for walk-through IRT scanning/screening systems at airports and border crossings, particularly as the point prevalence of fever in such subjects would be very low.

Item response theory in personality assessment: a demonstration using the MMPI-2 depression scale.

PubMed

Childs, R A; Dahlstrom, W G; Kemp, S M; Panter, A T

2000-03-01

Item response theory (IRT) analyses have, over the past 3 decades, added much to our understanding of the relationships among and characteristics of test items, as revealed in examinees response patterns. Assessment instruments used outside the educational context have only infrequently been analyzed using IRT, however. This study demonstrates the relevance of IRT to personality data through analyses of Scale 2 (the Depression Scale) on the revised Minnesota Multiphasic Personality Inventory (MMPI-2). A rich set of hypotheses regarding the items on this scale, including contrasts among the Harris-Lingoes and Wiener-Harmon subscales and differences in the items measurement characteristics for men and women, are investigated through the IRT analyses.

Using item response theory to investigate the structure of anticipated affect: do self-reports about future affective reactions conform to typical or maximal models?

PubMed

Zampetakis, Leonidas A; Lerakis, Manolis; Kafetsios, Konstantinos; Moustakis, Vassilis

2015-01-01

In the present research, we used item response theory (IRT) to examine whether effective predictions (anticipated affect) conforms to a typical (i.e., what people usually do) or a maximal behavior process (i.e., what people can do). The former, correspond to non-monotonic ideal point IRT models, whereas the latter correspond to monotonic dominance IRT models. A convenience, cross-sectional student sample (N = 1624) was used. Participants were asked to report on anticipated positive and negative affect around a hypothetical event (emotions surrounding the start of a new business). We carried out analysis comparing graded response model (GRM), a dominance IRT model, against generalized graded unfolding model, an unfolding IRT model. We found that the GRM provided a better fit to the data. Findings suggest that the self-report responses to anticipated affect conform to dominance response process (i.e., maximal behavior). The paper also discusses implications for a growing literature on anticipated affect.

Geometrical Characteristics of Cd-Rich Inclusion Defects in CdZnTe Materials

NASA Astrophysics Data System (ADS)

Xu, Chao; Sheng, Fengfeng; Yang, Jianrong

2017-08-01

The geometrical characteristics of Cd-rich inclusion defects in CdZnTe crystals have been investigated by infrared transmission (IRT) microscopy and chemical etching methods, revealing that they are composed of a Cd-rich inclusion core zone with high dislocation density and defect extension belts. Based on the experimental results, the orientation and shape of these belts were determined, showing that their extension directions in three-dimensional (3-D) space are along <211> crystal orientation. To explain the observed IRT images of Cd-rich inclusion defects, a 3-D model with plate-shaped structure for dislocation extension belts is proposed. Greyscale IRT images of dislocation extension belts thus depend on their absorption layer thickness. Assuming that defects can be discerned by IRT microscopy only when their absorption layer thickness is greater than twice that of the plate-shaped dislocation extension belts, this 3-D defect model can rationalize the IRT images of Cd-rich inclusion defects.

Using item response theory to investigate the structure of anticipated affect: do self-reports about future affective reactions conform to typical or maximal models?

PubMed Central

Zampetakis, Leonidas A.; Lerakis, Manolis; Kafetsios, Konstantinos; Moustakis, Vassilis

2015-01-01

In the present research, we used item response theory (IRT) to examine whether effective predictions (anticipated affect) conforms to a typical (i.e., what people usually do) or a maximal behavior process (i.e., what people can do). The former, correspond to non-monotonic ideal point IRT models, whereas the latter correspond to monotonic dominance IRT models. A convenience, cross-sectional student sample (N = 1624) was used. Participants were asked to report on anticipated positive and negative affect around a hypothetical event (emotions surrounding the start of a new business). We carried out analysis comparing graded response model (GRM), a dominance IRT model, against generalized graded unfolding model, an unfolding IRT model. We found that the GRM provided a better fit to the data. Findings suggest that the self-report responses to anticipated affect conform to dominance response process (i.e., maximal behavior). The paper also discusses implications for a growing literature on anticipated affect. PMID:26441806

Methods for Equating Mental Tests.

DTIC Science & Technology

1984-11-01

1983) compared conventional and IRT methods for equating the Test of English as a Foreign Language ( TOEFL ) after chaining. Three conventional and...three IRT equating methods were examined in this study; two sections of TOEFL were each (separately) equated. The IRT methods included the following: (a...group. A separate base form was established for each of the six equating methods. Instead of equating the base-form TOEFL to itself, the last (eighth

Effect of Item Response Theory (IRT) Model Selection on Testlet-Based Test Equating. Research Report. ETS RR-14-19

ERIC Educational Resources Information Center

Cao, Yi; Lu, Ru; Tao, Wei

2014-01-01

The local item independence assumption underlying traditional item response theory (IRT) models is often not met for tests composed of testlets. There are 3 major approaches to addressing this issue: (a) ignore the violation and use a dichotomous IRT model (e.g., the 2-parameter logistic [2PL] model), (b) combine the interdependent items to form a…

Aero-Thermal Calibration of the NASA Glenn Icing Research Tunnel (2012 Tests)

NASA Technical Reports Server (NTRS)

Pastor-Barsi, Christine; Allen, Arrington E.

2013-01-01

A full aero-thermal calibration of the NASA Glenn Icing Research Tunnel (IRT) was completed in 2012 following the major modifications to the facility that included replacement of the refrigeration plant and heat exchanger. The calibration test provided data used to fully document the aero-thermal flow quality in the IRT test section and to construct calibration curves for the operation of the IRT.

A new network of faint calibration stars from the near infrared spectrometer (NIRS) on the IRTS

NASA Technical Reports Server (NTRS)

Freund, Minoru M.; Matsuura, Mikako; Murakami, Hiroshi; Cohen, Martin; Noda, Manabu; Matsuura, Shuji; Matsumoto, Toshio

1997-01-01

The point source extraction and calibration of the near infrared spectrometer (NIRS) onboard the Infrared Telescope in Space (IRTS) is described. About 7 percent of the sky was observed during a one month mission in the range of 1.4 micrometers to 4 micrometers. The accuracy of the spectral shape and absolute values of calibration stars provided by the NIRS/IRTS were validated.

Inoculation with Bacillus subtilis and Azospirillum brasilense produces abscisic acid that reduces IRT1-mediated cadmium uptake of roots.

PubMed

Xu, Qianru; Pan, Wei; Zhang, Ranran; Lu, Qi; Xue, Wanlei; Wu, Cainan; Song, Bixiu; Du, Shaoting

2018-05-08

Cadmium (Cd) contamination of agricultural soils represents a serious risk to crop safety. A new strategy using abscisic acid (ABA)-generating bacteria, Bacillus subtilis or Azospirillum brasilense, was developed to reduce the Cd accumulation in plants grown in Cd-contaminated soil. Inoculation with either bacterium resulted in a pronounced increase in the ABA level in wild-type Arabidopsis Col-0 plants, accompanied by a decrease in Cd levels in plant tissues, which mitigated the Cd toxicity. As a consequence, the growth of plants exposed to Cd was improved. Nevertheless, B. subtilis and A. brasilense inoculation had little effect on Cd levels and toxicity in the ABA-insensitive mutant snrk 2.2/2.3, indicating that the action of ABA is required for these bacteria to reduce Cd accumulation in plants. Furthermore, inoculation with either B. subtilis or A. brasilense down-regulated the expression of IRT1 (IRON-REGULATED TRANSPORTER 1) in the roots of wild-type plants and had little effect on Cd levels in the IRT1-knockout mutants irt1-1 and irt1-2. In summary, we conclude that B. subtilis and A. brasilense can reduce Cd levels in plants via an IRT1-dependent ABA-mediated mechanism.

Efficacy of a cognitive-behavioral treatment for insomnia and nightmares in Afghanistan and Iraq veterans with PTSD.

PubMed

Margolies, Skye Ochsner; Rybarczyk, Bruce; Vrana, Scott R; Leszczyszyn, David J; Lynch, John

2013-10-01

Sleep disturbances are a core and salient feature of posttraumatic stress disorder (PTSD). Pilot studies have indicated that combined cognitive-behavioral therapy for insomnia (CBT-I) and imagery rehearsal therapy (IRT) for nightmares improves sleep as well as PTSD symptoms. The present study randomized 40 combat veterans (mean age 37.7 years; 90% male and 60% African American) who served in Afghanistan and/or Iraq (Operation Enduring Freedom [OEF]/Operation Iraqi Freedom [OIF]) to 4 sessions of CBT-I with adjunctive IRT or a waitlist control group. Two thirds of participants had nightmares at least once per week and received the optional IRT module. At posttreatment, veterans who participated in CBT-I/IRT reported improved subjectively and objectively measured sleep, a reduction in PTSD symptom severity and PTSD-related nighttime symptoms, and a reduction in depression and distressed mood compared to the waitlist control group. The findings from this first controlled study with OEF/OIF veterans suggest that CBT-I combined with adjunctive IRT may hold promise for reducing both insomnia and PTSD symptoms. Given the fact that only half of the patients with nightmares fully implemented the brief IRT protocol, future studies should determine if this supplement adds differential efficacy to CBT-I alone. © 2013 Wiley Periodicals, Inc.

Can Handheld Thermal Imaging Technology Improve Detection of Poachers in African Bushveldt?

PubMed Central

Dandy, Shantelle; Stubbs, Hannah; MacTavish, Dougal; MacTavish, Lynne

2015-01-01

Illegal hunting (poaching) is a global threat to wildlife. Anti-poaching initiatives are making increasing use of technology, such as infrared thermography (IRT), to support traditional foot and vehicle patrols. To date, the effectiveness of IRT for poacher location has not been tested under field conditions, where thermal signatures are often complex. Here, we test the hypothesis that IRT will increase the distance over which a poacher hiding in African scrub bushveldt can be detected relative to a conventional flashlight. We also test whether any increase in effectiveness is related to the cost and complexity of the equipment by comparing comparatively expensive (22000 USD) and relatively inexpensive (2000 USD) IRT devices. To test these hypotheses we employ a controlled, fully randomised, double-blind procedure to find a poacher in nocturnal field conditions in African bushveldt. Each of our 27 volunteer observers walked three times along a pathway using one detection technology on each pass in randomised order. They searched a prescribed search area of bushveldt within which the target was hiding. Hiding locations were pre-determined, randomised, and changed with each pass. Distances of first detection and positive detection were noted. All technologies could be used to detect the target. Average first detection distance for flashlight was 37.3m, improving by 19.8m to 57.1m using LIRT and by a further 11.2m to 68.3m using HIRT. Although detection distances were significantly greater for both IRTs compared to flashlight, there was no significant difference between LIRT and HIRT. False detection rates were low and there was no significant association between technology and accuracy of detection. Although IRT technology should ideally be tested in the specific environment intended before significant investment is made, we conclude that IRT technology is promising for anti-poaching patrols and that for this purpose low cost IRT units are as effective as units ten times more expensive. PMID:26110865

An Exploratory Analysis of Functional Staging Using an Item Response Theory Approach

PubMed Central

Tao, Wei; Haley, Stephen M.; Coster, Wendy J.; Ni, Pengsheng; Jette, Alan M.

2009-01-01

Objectives To develop and explore the feasibility of a functional staging system (defined as the process of assigning subjects, according to predetermined standards, into a set of hierarchical levels with regard to their functioning performance in mobility, daily activities, and cognitive skills) based on item response theory (IRT) methods using short-forms of the Activity Measure for Post-Acute Care (AM-PAC); and to compare the criterion validity and sensitivity of the IRT-based staging system to a non-IRT-based staging system developed for the FIM instrument. Design Prospective, longitudinal cohort study of patients interviewed at hospital discharge and 1, 6, and 12 months after inpatient rehabilitation. Setting Follow-up interviews conducted in patients’ homes. Participants Convenience sample of 516 patients (47% men; sample mean age, 68.3y) at baseline (retention at the final follow-up, 65%) with neurologic, lower-extremity orthopedic, or complex medical conditions. Interventions Not applicable Main Outcome Measures AM-PAC basic mobility, daily activity, and applied cognitive activity stages; FIM executive control, mobility, activities of daily living, and sphincter stages. Stages refer to the hierarchical levels assigned to patient’s functioning performance. Results We were able to define IRT-based staging definitions and create meaningful cut scores based on the 3 AM-PAC short-forms. The IRT stages correlated as well or better to the criterion items than the FIM stages. Both the IRT-based stages and the FIM stages were sensitive to changes throughout the 6-month follow-up period. The FIM stages were more sensitive in detecting changes between baseline and 1-month follow-up visit. The AM-PAC stages were more discriminant in the follow-up visits. Conclusions An IRT-based staging approach appeared feasible and effective in classifying patients throughout long-term follow-up. Although these stages were developed from short-forms, this staging methodology could also be applied to improve the meaning of scores generated from IRT-based computerized adaptive testing in future work. PMID:18503798

Measurement Equivalence in ADL and IADL Difficulty Across International Surveys of Aging: Findings From the HRS, SHARE, and ELSA

PubMed Central

Kasper, Judith D.; Brandt, Jason; Pezzin, Liliana E.

2012-01-01

Objective. To examine the measurement equivalence of items on disability across three international surveys of aging. Method. Data for persons aged 65 and older were drawn from the Health and Retirement Survey (HRS, n = 10,905), English Longitudinal Study of Aging (ELSA, n = 5,437), and Survey of Health, Ageing and Retirement in Europe (SHARE, n = 13,408). Differential item functioning (DIF) was assessed using item response theory (IRT) methods for activities of daily living (ADL) and instrumental activities of daily living (IADL) items. Results. HRS and SHARE exhibited measurement equivalence, but 6 of 11 items in ELSA demonstrated meaningful DIF. At the scale level, this item-level DIF affected scores reflecting greater disability. IRT methods also spread out score distributions and shifted scores higher (toward greater disability). Results for mean disability differences by demographic characteristics, using original and DIF-adjusted scores, were the same overall but differed for some subgroup comparisons involving ELSA. Discussion. Testing and adjusting for DIF is one means of minimizing measurement error in cross-national survey comparisons. IRT methods were used to evaluate potential measurement bias in disability comparisons across three international surveys of aging. The analysis also suggested DIF was mitigated for scales including both ADL and IADL and that summary indexes (counts of limitations) likely underestimate mean disability in these international populations. PMID:22156662

Evaluation of a preliminary physical function item bank supported the expected advantages of the Patient-Reported Outcomes Measurement Information System (PROMIS).

PubMed

Rose, M; Bjorner, J B; Becker, J; Fries, J F; Ware, J E

2008-01-01

The Patient-Reported Outcomes Measurement Information System (PROMIS) was initiated to improve precision, reduce respondent burden, and enhance the comparability of health outcomes measures. We used item response theory (IRT) to construct and evaluate a preliminary item bank for physical function assuming four subdomains. Data from seven samples (N=17,726) using 136 items from nine questionnaires were evaluated. A generalized partial credit model was used to estimate item parameters, which were normed to a mean of 50 (SD=10) in the US population. Item bank properties were evaluated through Computerized Adaptive Test (CAT) simulations. IRT requirements were fulfilled by 70 items covering activities of daily living, lower extremity, and central body functions. The original item context partly affected parameter stability. Items on upper body function, and need for aid or devices did not fit the IRT model. In simulations, a 10-item CAT eliminated floor and decreased ceiling effects, achieving a small standard error (< 2.2) across scores from 20 to 50 (reliability >0.95 for a representative US sample). This precision was not achieved over a similar range by any comparable fixed length item sets. The methods of the PROMIS project are likely to substantially improve measures of physical function and to increase the efficiency of their administration using CAT.

Better assessment of physical function: item improvement is neglected but essential

PubMed Central

2009-01-01

Introduction Physical function is a key component of patient-reported outcome (PRO) assessment in rheumatology. Modern psychometric methods, such as Item Response Theory (IRT) and Computerized Adaptive Testing, can materially improve measurement precision at the item level. We present the qualitative and quantitative item-evaluation process for developing the Patient Reported Outcomes Measurement Information System (PROMIS) Physical Function item bank. Methods The process was stepwise: we searched extensively to identify extant Physical Function items and then classified and selectively reduced the item pool. We evaluated retained items for content, clarity, relevance and comprehension, reading level, and translation ease by experts and patient surveys, focus groups, and cognitive interviews. We then assessed items by using classic test theory and IRT, used confirmatory factor analyses to estimate item parameters, and graded response modeling for parameter estimation. We retained the 20 Legacy (original) Health Assessment Questionnaire Disability Index (HAQ-DI) and the 10 SF-36's PF-10 items for comparison. Subjects were from rheumatoid arthritis, osteoarthritis, and healthy aging cohorts (n = 1,100) and a national Internet sample of 21,133 subjects. Results We identified 1,860 items. After qualitative and quantitative evaluation, 124 newly developed PROMIS items composed the PROMIS item bank, which included revised Legacy items with good fit that met IRT model assumptions. Results showed that the clearest and best-understood items were simple, in the present tense, and straightforward. Basic tasks (like dressing) were more relevant and important versus complex ones (like dancing). Revised HAQ-DI and PF-10 items with five response options had higher item-information content than did comparable original Legacy items with fewer response options. IRT analyses showed that the Physical Function domain satisfied general criteria for unidimensionality with one-, two-, three-, and four-factor models having comparable model fits. Correlations between factors in the test data sets were > 0.90. Conclusions Item improvement must underlie attempts to improve outcome assessment. The clear, personally important and relevant, ability-framed items in the PROMIS Physical Function item bank perform well in PRO assessment. They will benefit from further study and application in a wider variety of rheumatic diseases in diverse clinical groups, including those at the extremes of physical functioning, and in different administration modes. PMID:20015354

Better assessment of physical function: item improvement is neglected but essential.

PubMed

Bruce, Bonnie; Fries, James F; Ambrosini, Debbie; Lingala, Bharathi; Gandek, Barbara; Rose, Matthias; Ware, John E

2009-01-01

Physical function is a key component of patient-reported outcome (PRO) assessment in rheumatology. Modern psychometric methods, such as Item Response Theory (IRT) and Computerized Adaptive Testing, can materially improve measurement precision at the item level. We present the qualitative and quantitative item-evaluation process for developing the Patient Reported Outcomes Measurement Information System (PROMIS) Physical Function item bank. The process was stepwise: we searched extensively to identify extant Physical Function items and then classified and selectively reduced the item pool. We evaluated retained items for content, clarity, relevance and comprehension, reading level, and translation ease by experts and patient surveys, focus groups, and cognitive interviews. We then assessed items by using classic test theory and IRT, used confirmatory factor analyses to estimate item parameters, and graded response modeling for parameter estimation. We retained the 20 Legacy (original) Health Assessment Questionnaire Disability Index (HAQ-DI) and the 10 SF-36's PF-10 items for comparison. Subjects were from rheumatoid arthritis, osteoarthritis, and healthy aging cohorts (n = 1,100) and a national Internet sample of 21,133 subjects. We identified 1,860 items. After qualitative and quantitative evaluation, 124 newly developed PROMIS items composed the PROMIS item bank, which included revised Legacy items with good fit that met IRT model assumptions. Results showed that the clearest and best-understood items were simple, in the present tense, and straightforward. Basic tasks (like dressing) were more relevant and important versus complex ones (like dancing). Revised HAQ-DI and PF-10 items with five response options had higher item-information content than did comparable original Legacy items with fewer response options. IRT analyses showed that the Physical Function domain satisfied general criteria for unidimensionality with one-, two-, three-, and four-factor models having comparable model fits. Correlations between factors in the test data sets were > 0.90. Item improvement must underlie attempts to improve outcome assessment. The clear, personally important and relevant, ability-framed items in the PROMIS Physical Function item bank perform well in PRO assessment. They will benefit from further study and application in a wider variety of rheumatic diseases in diverse clinical groups, including those at the extremes of physical functioning, and in different administration modes.

The Organization of Controller Motifs Leading to Robust Plant Iron Homeostasis

PubMed Central

Agafonov, Oleg; Selstø, Christina Helen; Thorsen, Kristian; Xu, Xiang Ming; Drengstig, Tormod; Ruoff, Peter

2016-01-01

Iron is an essential element needed by all organisms for growth and development. Because iron becomes toxic at higher concentrations iron is under homeostatic control. Plants face also the problem that iron in the soil is tightly bound to oxygen and difficult to access. Plants have therefore developed special mechanisms for iron uptake and regulation. During the last years key components of plant iron regulation have been identified. How these components integrate and maintain robust iron homeostasis is presently not well understood. Here we use a computational approach to identify mechanisms for robust iron homeostasis in non-graminaceous plants. In comparison with experimental results certain control arrangements can be eliminated, among them that iron homeostasis is solely based on an iron-dependent degradation of the transporter IRT1. Recent IRT1 overexpression experiments suggested that IRT1-degradation is iron-independent. This suggestion appears to be misleading. We show that iron signaling pathways under IRT1 overexpression conditions become saturated, leading to a breakdown in iron regulation and to the observed iron-independent degradation of IRT1. A model, which complies with experimental data places the regulation of cytosolic iron at the transcript level of the transcription factor FIT. Including the experimental observation that FIT induces inhibition of IRT1 turnover we found a significant improvement in the system’s response time, suggesting a functional role for the FIT-mediated inhibition of IRT1 degradation. By combining iron uptake with storage and remobilization mechanisms a model is obtained which in a concerted manner integrates iron uptake, storage and remobilization. In agreement with experiments the model does not store iron during its high-affinity uptake. As an iron biofortification approach we discuss the possibility how iron can be accumulated even during high-affinity uptake. PMID:26800438

Item response theory analysis of Centers for Disease Control and Prevention Health-Related Quality of Life (CDC HRQOL) items in adults with arthritis.

PubMed

Mielenz, Thelma J; Callahan, Leigh F; Edwards, Michael C

2016-03-12

Examine the feasibility of performing an item response theory (IRT) analysis on two of the Centers for Disease Control and Prevention health-related quality of life (CDC HRQOL) modules - the 4-item Healthy Days Core Module (HDCM) and the 5-item Healthy days Symptoms Module (HDSM). Previous principal components analyses confirm that the two scales both assess a mix of mental (CDC-MH) and physical health (CDC-PH). The purpose is to conduct item response theory (IRT) analysis on the CDC-MH and CDC-PH scales separately. 2182 patients with self-reported or physician-diagnosed arthritis completed a cross-sectional survey including HDCM and HDSM items. Besides global health, the other 8 items ask the number of days that some statement was true; we chose to recode the data into 8 categories based on observed clustering. The IRT assumptions were assessed using confirmatory factor analysis and the data could be modeled using an unidimensional IRT model. The graded response model was used for IRT analyses and CDC-MH and CDC-PH scales were analyzed separately in flexMIRT. The IRT parameter estimates for the five-item CDC-PH all appeared reasonable. The three-item CDC-MH did not have reasonable parameter estimates. The CDC-PH scale is amenable to IRT analysis but the existing The CDC-MH scale is not. We suggest either using the 4-item Healthy Days Core Module (HDCM) and the 5-item Healthy days Symptoms Module (HDSM) as they currently stand or the CDC-PH scale alone if the primary goal is to measure physical health related HRQOL.

Use of Laser Speckle Contrast Imaging to Assess Digital Microvascular Function in Primary Raynaud Phenomenon and Systemic Sclerosis: A Comparison Using the Raynaud Condition Score Diary.

PubMed

Pauling, John D; Shipley, Jacqueline A; Hart, Darren J; McGrogan, Anita; McHugh, Neil J

2015-07-01

Evaluate objective assessment of digital microvascular function using laser speckle contrast imaging (LSCI) in a cross-sectional study of patients with primary Raynaud phenomenon (RP) and systemic sclerosis (SSc), comparing LSCI with both infrared thermography (IRT) and subjective assessment using the Raynaud Condition Score (RCS) diary. Patients with SSc (n = 25) and primary RP (n = 18) underwent simultaneous assessment of digital perfusion using LSCI and IRT with a cold challenge on 2 occasions, 2 weeks apart. The RCS diary was completed between assessments. The relationship between objective and subjective assessments of RP was evaluated. Reproducibility of LSCI/IRT was assessed, along with differences between primary RP and SSc, and the effect of sex. There was moderate-to-good correlation between LSCI and IRT (Spearman rho 0.58-0.84, p < 0.01), but poor correlation between objective assessments and the RCS diary (p > 0.05 for all analyses). Reproducibility of IRT and LSCI was moderate at baseline (ICC 0.51-0.63) and immediately following cold challenge (ICC 0.56-0.86), but lower during reperfusion (ICC 0.3-0.7). Neither subjective nor objective assessments differentiated between primary RP and SSc. Men reported lower median daily frequency of RP attacks (0.82 vs 1.93, p = 0.03). Perfusion using LSCI/IRT was higher in men for the majority of assessments. Objective and subjective methods provide differing information on microvascular function in RP. There is good convergent validity of LSCI with IRT and acceptable reproducibility of both modalities. Neither subjective nor objective assessments could differentiate between primary RP and SSc. Influence of sex on subjective and objective assessment of RP warrants further evaluation.

Genetic and clinical features of false-negative infants in a neonatal screening programme for cystic fibrosis.

PubMed

Padoan, R; Genoni, S; Moretti, E; Seia, M; Giunta, A; Corbetta, C

2002-01-01

A study was performed on the delayed diagnosis of cystic fibrosis (CF) in infants who had false-negative results in a neonatal screening programme. The genetic and clinical features of false-negative infants in this screening programme were assessed together with the efficiency of the screening procedure in the Lombardia region. In total, 774,687 newborns were screened using a two-step immunoreactive trypsinogen (IRT) (in the years 1990-1992), IRT/IRT + delF508 (1993-1998) or IRT/IRT + polymerase chain reaction (PCR) and oligonucleotide ligation assay (OLA) protocol (1998-1999). Out of 196 CF children born in the 10 y period 15 were false negative on screening (7.6%) and molecular analysis showed a high variability in the genotypes. The cystic fibrosis transmembrane regulator (CFTR) gene mutations identified were delF508, D1152H, R1066C, R334W, G542X, N1303K, F1052V, A120T, 3849 + 10kbC --> T, 2789 + 5G --> A, 5T-12TG and the novel mutation D110E. In three patients no mutation was identified after denaturing gradient gel electrophoresis of the majority of CFTR gene exons. The clinical phenotypes of CF children diagnosed by their symptoms at different ages were very mild. None of them presented with a severe lung disease. The majority of them did not seem to have been damaged by the delayed diagnosis. The combination of IRT assay plus genotype analysis (1998-1999) appears to be a more reliable method of detecting CF than IRT measurement alone or combined with only the delF508 mutation.

Evidence for a causal relationship between early exocrine pancreatic disease and cystic fibrosis-related diabetes: a Mendelian randomization study.

PubMed

Soave, David; Miller, Melissa R; Keenan, Katherine; Li, Weili; Gong, Jiafen; Ip, Wan; Accurso, Frank; Sun, Lei; Rommens, Johanna M; Sontag, Marci; Durie, Peter R; Strug, Lisa J

2014-06-01

Circulating immunoreactive trypsinogen (IRT), a biomarker of exocrine pancreatic disease in cystic fibrosis (CF), is elevated in most CF newborns. In those with severe CF transmembrane conductance regulator (CFTR) genotypes, IRT declines rapidly in the first years of life, reflecting progressive pancreatic damage. Consistent with this progression, a less elevated newborn IRT measure would reflect more severe pancreatic disease, including compromised islet compartments, and potentially increased risk of CF-related diabetes (CFRD). We show in two independent CF populations that a lower newborn IRT estimate is associated with higher CFRD risk among individuals with severe CFTR genotypes, and we provide evidence to support a causal relationship. Increased loge(IRT) at birth was associated with decreased CFRD risk in Canadian and Colorado samples (hazard ratio 0.30 [95% CI 0.15-0.61] and 0.39 [0.18-0.81], respectively). Using Mendelian randomization with the SLC26A9 rs7512462 genotype as an instrumental variable since it is known to be associated with IRT birth levels in the CF population, we provide evidence to support a causal contribution of exocrine pancreatic status on CFRD risk. Our findings suggest CFRD risk could be predicted in early life and that maintained ductal fluid flow in the exocrine pancreas could delay the onset of CFRD. © 2014 by the American Diabetes Association.

Scale Model Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Canacci, Victor A.

1997-01-01

NASA Lewis Research Center's Icing Research Tunnel (IRT) is the world's largest refrigerated wind tunnel and one of only three icing wind tunnel facilities in the United States. The IRT was constructed in the 1940's and has been operated continually since it was built. In this facility, natural icing conditions are duplicated to test the effects of inflight icing on actual aircraft components as well as on models of airplanes and helicopters. IRT tests have been used successfully to reduce flight test hours for the certification of ice-detection instrumentation and ice protection systems. To ensure that the IRT will remain the world's premier icing facility well into the next century, Lewis is making some renovations and is planning others. These improvements include modernizing the control room, replacing the fan blades with new ones to increase the test section maximum velocity to 430 mph, installing new spray bars to increase the size and uniformity of the artificial icing cloud, and replacing the facility heat exchanger. Most of the improvements will have a first-order effect on the IRT's airflow quality. To help us understand these effects and evaluate potential improvements to the flow characteristics of the IRT, we built a modular 1/10th-scale aerodynamic model of the facility. This closed-loop scale-model pilot tunnel was fabricated onsite in the various shops of Lewis' Fabrication Support Division. The tunnel's rectangular sections are composed of acrylic walls supported by an aluminum angle framework. Its turning vanes are made of tubing machined to the contour of the IRT turning vanes. The fan leg of the tunnel, which transitions from rectangular to circular and back to rectangular cross sections, is fabricated of fiberglass sections. The contraction section of the tunnel is constructed from sheet aluminum. A 12-bladed aluminum fan is coupled to a turbine powered by high-pressure air capable of driving the maximum test section velocity to 550 ft/sec (Mach 0.45). The air turbine and instrumentation are housed inside a fiberglass nacelle. Total and static pressure measurements can be taken around the loop, and velocity and flow angularity measurements can be taken with hot-wire and five-hole probes at specific locations. The Scale Model Icing Research Tunnel (SMIRT) is undergoing checkout tests to determine how its airflow characteristics compare with the IRT. Near-term uses for this scale-model tunnel include determining the aerodynamic effects of replacing the 52-yearold W-shaped heat exchanger with a flat-faced heat exchanger. SMIRT is an integral part of the improvements planned for the IRT because testing the proposed IRT improvements in a scale-model tunnel will lower costs and improve productivity.

Optical flare events on the RS Canum Venaticorum star UX Arietis

NASA Astrophysics Data System (ADS)

Cao, Dong-Tao; Gu, Sheng-Hong

2017-05-01

Based on long-term high-resolution spectroscopic observations obtained during five observing runs from 2001 to 2004, we study optical flare events and chromospheric activity variability of the very active RS CVn star UX Ari. By means of the spectral subtraction technique, several optical chromospheric activity indicators (including the He i D3, Na i D1, D2 doublet, Hα and Ca ii IRT lines) covered in our echelle spectra were analyzed. Four large optical flare events were detected on UX Ari during our observations, which show prominent He i D3 line emission together with great enhancement in emission of the Hα and Ca ii IRT lines and strong filled-in or emission reversal features in the Na i D1, D2 doublet lines. The newly detected flares are much more energetic than previous discoveries, especially for the flare identified during the 2002 December observing run. Optical flare events on UX Ari are more likely to be observed around two quadratures of the system, except for our optical flares detected during the 2004 November observing run. Moreover, we have found rotational modulation of chromospheric activity in the Hα and Ca ii IRT lines, which suggests the presence of chromospherically active longitudes over the surface of UX Ari. The change in chromospherically active longitudes among our observing runs, as well as the variation in chromospheric activity level from 2001 to 2004, indicates a long-term evolution of active regions.

Instability resistance training across the exercise continuum.

PubMed

Behm, David G; Colado, Juan C; Colado, Juan C

2013-11-01

Instability resistance training (IRT; unstable surfaces and devices to strengthen the core or trunk muscles) is popular in fitness training facilities. To examine contradictory IRT recommendations for health enthusiasts and rehabilitation. A literature search was performed using MEDLINE, SPORT Discus, ScienceDirect, Web of Science, and Google Scholar databases from 1990 to 2012. Databases were searched using key terms, including "balance," "stability," "instability," "resistance training," "core," "trunk," and "functional performance." Additionally, relevant articles were extracted from reference lists. To be included, research questions addressed the effect of balance or IRT on performance, healthy and active participants, and physiologic or performance outcome measures and had to be published in English in a peer-reviewed journal. There is a dichotomy of opinions on the effectiveness and application of instability devices and conditions for health and performance training. Balance training without resistance has been shown to improve not only balance but functional performance as well. IRT studies document similar training adaptations as stable resistance training programs with recreationally active individuals. Similar progressions with lower resistance may improve balance and stability, increase core activation, and improve motor control. IRT is highly recommended for youth, elderly, recreationally active individuals, and highly trained enthusiasts.

Centuries of domestication has not impaired oviposition site-selection function in the silkmoth, Bombyx mori

PubMed Central

Damodaram, Kamala Jayanthi Pagadala; Kempraj, Vivek; Aurade, Ravindra Mahadappa; Rajasekhar, Sowmya Bandhisara; Venkataramanappa, Ravindra Kothapalli; Nandagopal, Bakthavatsalam; Verghese, Abraham

2014-01-01

Oviposition site-selection in insects is mediated through innate recognition templates (IRTs) tuned to specific chemical cues. These cues aid gravid insects in choosing suitable oviposition sites and may even enhance the fitness of their offspring by warding off predators and parasitoids. However, studies on the evolution of oviposition site-selection and cues instigating oviposition in domesticated insects remain elusive. Using the interaction between the silkmoth, Bombyx mori, and its host plant mulberry, Morus alba, as a model system, we demonstrate that centuries of domestication of silkmoth has not impaired its oviposition site-selection function. Silkmoths significantly preferred mulberry leaves to filter paper as oviposition sites. Oviposition assays with filter paper, filter paper treated with leaf volatiles and leaf alone proved that surface texture was not a significant criterion for oviposition site-selection, but volatile cues were. Oviposition assays with electrophysiologically active compounds from mulberry revealed that two of the volatiles, valencene and α-humulene, aided moths in choosing suitable oviposition sites and enhanced egg-laying significantly. Moreover, we show that generalist egg-parasitoids are strongly repelled by valencene and α-humulene. Our results demonstrate that IRTs tuned to cues that aid crucial functions like oviposition site-selection are less likely to be impaired even after centuries of domestication. PMID:25503440

Intensive remote monitoring versus conventional care in type 1 diabetes: A randomized controlled trial.

PubMed

Gandrud, Laura; Altan, Aylin; Buzinec, Paul; Hemphill, Jesse; Chatterton, Jayne; Kelley, Tina; Vojta, Deneen

2018-02-21

While frequent contact with diabetes care providers may improve glycemic control among patients with type 1 diabetes (T1D), in-person visits are labor-intensive and costly. This study was conducted to assess the impact of an intensive remote therapy (IRT) intervention for pediatric patients with T1D. Pediatric patients with T1D were randomized to IRT or conventional care (CC) for 6 months. Both cohorts continued routine quarterly clinic visits and uploaded device data; for the IRT cohort, data were reviewed and patients were contacted if regimen adjustments were indicated. Glycated hemoglobin (HbA1c) change from baseline was assessed at 6 and 9 months. Diabetes-related quality of life (QoL), healthcare services utilization, and hypoglycemic events were also tracked. Among 117 enrollees (60 IRT, 57 CC), mean (SD) 6-month %HbA1c change for IRT vs CC was -0.34 (0.85) (-3.7 mmol/mol) vs -0.05 (0.74) (-0.5 mmol/mol) overall (P = .071); -0.15 (0.67) (1.6 mmol/mol) vs -0.02 (0.66) (0.2 mmol/mol) for ages 8 to 12 (P = .541); and -0.50 (0.95) (-5.5 mmol/mol) vs -0.06 (0.80) (-0.7 mmol/mol) for ages 13 to 17 (P = .056). Diabetes-related QoL increased by 6.5 and 1.3 points for IRT and CC, respectively (P = .062). Three months after intervention cessation, %HbA1c changed minimally among treated children aged 8 to 12 but increased by 0.22 (0.89) (2.4 mmol/mol) among those aged 13 to 17. IRT substantially affected diabetes metrics and improved QoL among pediatric patients with T1D. Adolescents experienced a stronger treatment effect, but had difficulty in sustaining improved control after intervention cessation. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The quetiapine active metabolite N-desalkylquetiapine and the neurotensin NTS₁ receptor agonist PD149163 exhibit antidepressant-like effects on operant responding in male rats.

PubMed

Hillhouse, Todd M; Shankland, Zachary; Matazel, Katelin S; Keiser, Ashley A; Prus, Adam J

2014-12-01

Major depressive disorder is the most common mood disorder in the United States and European Union; however, the limitations of clinically available antidepressant drugs have led researchers to pursue novel pharmacological treatments. Clinical studies have reported that monotherapy with the atypical antipsychotic drug quetiapine produces a rapid reduction in depressive symptoms that is apparent after 1 week of treatment, and it is possible that the active metabolite N-desalkylquetiapine, which structurally resembles an antidepressant drug, produces antidepressant effects. Neuropharmacological evaluations of the neurotensin NTS1 receptor agonist PD149163 suggest antidepressant efficacy, but the effects of a NTS₁ receptor agonist in an antidepressant animal model have yet to be reported. The present study examined the antidepressant-like effects of N-desalkylquetiapine, PD14916, quetiapine, the tricyclic antidepressant drug imipramine, the atypical antipsychotic drug risperidone, and the typical antipsychotic drug raclopride on responding in male Sprague-Dawley rats trained on a differential-reinforcement-of-low-rate 72-s operant schedule, a procedure used for screening antidepressant drugs. Quetiapine, PD149163, risperidone, and imipramine exhibited antidepressant-like effects by increasing the number of reinforcers earned, decreasing the number of responses emitted, and shifting the interresponse time (IRT) distributions to the right. N-Desalkylquetiapine produced a partial antidepressant-like effect by decreasing the number of responses emitted and producing a rightward shift in the IRT distributions, but it did not significantly alter the number of reinforcers earned. Raclopride decreased reinforcers and responses. These data suggest that N-desalkylquetiapine likely contributes to quetiapine's antidepressant efficacy and identify NTS₁ receptor activation as a potential novel pharmacologic strategy for antidepressant drugs. PsycINFO Database Record (c) 2014 APA, all rights reserved.

In-flight investigations of the unsteady behaviour of the boundary layer with infrared thermography

NASA Astrophysics Data System (ADS)

Szewczyk, Mariusz; Smusz, Robert; de Groot, Klaus; Meyer, Joerg; Kucaba-Pietal, Anna; Rzucidlo, Pawel

2017-04-01

Infrared thermography (IRT) has been well established in wind tunnel and flight tests for the last decade. Former applications of IRT were focused, in nearly all cases, on steady measurements. In the last years, requirements of unsteady IRT measurements (up to 10 Hz) have been formulated, but the problem of a very slow thermal response of common materials of wind tunnel models or airplane components has to be overcome by finding a surface modification with a fast thermal response (low heat capacity, low thermal conductivity and high thermal diffusivity). Therefore, lab investigations of potential material combinations and flight tests with a ‘low cost’ aircraft, i.e. a glider with a modified wing surface, were conducted. In order to induce unsteady conditions (rapid change of laminar-turbulent boundary layer transition), special maneuvers of a glider during IRT measurements were performed.

Pancreatic cellular injury after cardiac surgery with cardiopulmonary bypass: frequency, time course and risk factors.

PubMed

Nys, Monique; Venneman, Ingrid; Deby-Dupont, Ginette; Preiser, Jean-Charles; Vanbelle, Sophie; Albert, Adelin; Camus, Gérard; Damas, Pierre; Larbuisson, Robert; Lamy, Maurice

2007-05-01

Although often clinically silent, pancreatic cellular injury (PCI) is relatively frequent after cardiac surgery with cardiopulmonary bypass; and its etiology and time course are largely unknown. We defined PCI as the simultaneous presence of abnormal values of pancreatic isoamylase and immunoreactive trypsin (IRT). The frequency and time evolution of PCI were assessed in this condition using assays for specific exocrine pancreatic enzymes. Correlations with inflammatory markers were searched for preoperative risk factors. One hundred ninety-three patients submitted to cardiac surgery were enrolled prospectively. Blood IRT, amylase, pancreatic isoamylase, lipase, and markers of inflammation (alpha1-protease inhibitor, alpha2-macroglobulin, myeloperoxidase) were measured preoperatively and postoperatively until day 8. The postoperative increase in plasma levels of pancreatic enzymes and urinary IRT was biphasic in all patients: early after surgery and later (from day 4 to 8 after surgery). One hundred thirty-three patients (69%) experienced PCI, with mean IRT, isoamylase, and alpha1-protease inhibitor values higher for each sample than that in patients without PCI. By multiple regression analysis, we found preoperative values of plasma IRT >or=40 ng/mL, amylase >or=42 IU/mL, and pancreatic isoamylase >or=20 IU/L associated with a higher incidence of postsurgery PCI (P < 0.005). In the PCI patients, a significant correlation was found between the 4 pancreatic enzymes and urinary IRT, total calcium, myeloperoxidase, alpha1-protease inhibitor, and alpha2-macroglobulin. These data support a high prevalence of postoperative PCI after cardiac surgery with cardiopulmonary bypass, typically biphasic and clinically silent, especially when pancreatic enzymes were elevated preoperatively.

Differences of Cd uptake and expression of OAS and IRT genes in two varieties of ryegrasses.

PubMed

Chi, Sunlin; Qin, Yuli; Xu, Weihong; Chai, Yourong; Feng, Deyu; Li, Yanhua; Li, Tao; Yang, Mei; He, Zhangmi

2018-06-16

Pot experiment was conducted to study the difference of cadmium uptake and OAS and IRT genes' expression between the two ryegrass varieties under cadmium stress. The results showed that with the increase of cadmium levels, the dry weights of roots of the two ryegrass varieties, and the dry weights of shoots and plants of Abbott first increased and then decreased. When exposed to 75 mg kg -1 Cd, the dry weights of shoot and plant of Abbott reached the maximum, which increased by 11.13 and 10.67% compared with the control. At 75 mg kg -1 Cd, cadmium concentrations in shoot of the two ryegrass varieties were higher than the critical value of Cd hyperaccumulator (100 mg kg -1 ), 111.19 mg kg -1 (Bond), and 133.69 mg kg -1 (Abbott), respectively. The OAS gene expression in the leaves of the two ryegrass varieties showed a unimodal curve, which was up to the highest at the cadmium level of 150 mg kg -1 , but fell back at high cadmium levels of 300 and 600 mg kg -1 . The OAS gene expression in Bond and Abbott roots showed a bimodal curve. The OAS gene expression in Bond root and Abbott stem mainly showed a unimodal curve. The expression of IRT genes family in the leaves of ryegrass varieties was basically in line with the characteristics of unimodal curve, which was up to the highest at cadmium level of 75 or 150 mg kg -1 , respectively. The IRT expression in the ryegrass stems showed characteristics of bimodal and unimodal curves, while that in the roots was mainly unimodal. The expression of OAS and IRT genes was higher in Bond than that in Abbott due to genotype difference between the two varieties. The expression of OAS and IRT was greater in leaves than that in roots and stems. Ryegrass tolerance to cadmium can be increased by increasing the expression of OAS and IRT genes in roots and stems, and transfer of cadmium from roots and stems to the leaves can be enhanced by increasing expression OAS and IRT in leaves.

Standardized assessment of infrared thermographic fever screening system performance

NASA Astrophysics Data System (ADS)

Ghassemi, Pejhman; Pfefer, Joshua; Casamento, Jon; Wang, Quanzeng

2017-03-01

Thermal modalities represent the only currently viable mass fever screening approach for outbreaks of infectious disease pandemics such as Ebola and SARS. Non-contact infrared thermometers (NCITs) and infrared thermographs (IRTs) have been previously used for mass fever screening in transportation hubs such as airports to reduce the spread of disease. While NCITs remain a more popular choice for fever screening in the field and at fixed locations, there has been increasing evidence in the literature that IRTs can provide greater accuracy in estimating core body temperature if appropriate measurement practices are applied - including the use of technically suitable thermographs. Therefore, the purpose of this study was to develop a battery of evaluation test methods for standardized, objective and quantitative assessment of thermograph performance characteristics critical to assessing suitability for clinical use. These factors include stability, drift, uniformity, minimum resolvable temperature difference, and accuracy. Two commercial IRT models were characterized. An external temperature reference source with high temperature accuracy was utilized as part of the screening thermograph. Results showed that both IRTs are relatively accurate and stable (<1% error of reading with stability of +/-0.05°C). Overall, results of this study may facilitate development of standardized consensus test methods to enable consistent and accurate use of IRTs for fever screening.

Clinical applications of dynamic infrared thermography in plastic surgery: a systematic review

PubMed Central

John, Hannah Eliza; Niumsawatt, Vachara; Whitaker, Iain S.

2016-01-01

Background Infrared thermography (IRT) has become an increasingly utilized adjunct to more expensive and/or invasive investigations in a range of surgical fields, no more so than in plastic surgery. The combination of functional assessment, flow characteristics and anatomical localization has led to increasing applications of this technology. This article aims to perform a systematic review of the clinical applications of IRT in plastic surgery. Methods A systematic literature search using the keywords ‘IRT’ and ‘dynamic infrared thermography (DIRT)’ has been accomplished. A total of 147 papers were extracted from various medical databases, of which 34 articles were subjected to a full read by two independent reviewers, to ensure the papers satisfied the inclusion and exclusion criteria. Studies focusing on the use of IRT in breast cancer diagnosis were excluded. Results A systematic review of 29 publications demonstrated the clinical applications of IRT in plastic surgery today. They include preoperative planning of perforators for free flaps, post operative monitoring of free flaps, use of IRT as an adjunct in burns depth analysis, in assessment of response to treatment in hemangioma and as a diagnostic test for cutaneous melanoma and carpal tunnel syndrome (CTS). Conclusions Modern infrared imaging technology with improved standardization protocols is now a credible, useful non-invasive tool in clinical practice. PMID:27047781

Development and validation of an item response theory-based Social Responsiveness Scale short form.

PubMed

Sturm, Alexandra; Kuhfeld, Megan; Kasari, Connie; McCracken, James T

2017-09-01

Research and practice in autism spectrum disorder (ASD) rely on quantitative measures, such as the Social Responsiveness Scale (SRS), for characterization and diagnosis. Like many ASD diagnostic measures, SRS scores are influenced by factors unrelated to ASD core features. This study further interrogates the psychometric properties of the SRS using item response theory (IRT), and demonstrates a strategy to create a psychometrically sound short form by applying IRT results. Social Responsiveness Scale analyses were conducted on a large sample (N = 21,426) of youth from four ASD databases. Items were subjected to item factor analyses and evaluation of item bias by gender, age, expressive language level, behavior problems, and nonverbal IQ. Item selection based on item psychometric properties, DIF analyses, and substantive validity produced a reduced item SRS short form that was unidimensional in structure, highly reliable (α = .96), and free of gender, age, expressive language, behavior problems, and nonverbal IQ influence. The short form also showed strong relationships with established measures of autism symptom severity (ADOS, ADI-R, Vineland). Degree of association between all measures varied as a function of expressive language. Results identified specific SRS items that are more vulnerable to non-ASD-related traits. The resultant 16-item SRS short form may possess superior psychometric properties compared to the original scale and emerge as a more precise measure of ASD core symptom severity, facilitating research and practice. Future research using IRT is needed to further refine existing measures of autism symptomatology. © 2017 Association for Child and Adolescent Mental Health.

NDT detection and quantification of induced defects on composite helicopter rotor blade and UAV wing sections

NASA Astrophysics Data System (ADS)

Findeis, Dirk; Gryzagoridis, Jasson; Musonda, Vincent

2008-09-01

Digital Shearography and Infrared Thermography (IRT) techniques were employed to test non-destructively samples from aircraft structures of composite material nature. Background information on the techniques is presented and it is noted that much of the inspection work reviewed in the literature has focused on qualitative evaluation of the defects rather than quantitative. There is however, need to quantify the defects if the threshold rejection criterion of whether the component inspected is fit for service has to be established. In this paper an attempt to quantify induced defects on a helicopter main rotor blade and Unmanned Aerospace Vehicle (UAV) composite material is presented. The fringe patterns exhibited by Digital Shearography were used to quantify the defects by relating the number of fringes created to the depth of the defect or flaw. Qualitative evaluation of defects with IRT was achieved through a hot spot temperature indication above the flaw on the surface of the material. The results of the work indicate that the Shearographic technique proved to be more sensitive than the IRT technique. It should be mentioned that there is "no set standard procedure" tailored for testing of composites. Each composite material tested is more likely to respond differently to defect detection and this depends generally on the component geometry and a suitable selection of the loading system to suit a particular test. The experimental procedure that is reported in this paper can be used as a basis for designing a testing or calibration procedure for defects detection on any particular composite material component or structure.

Suppression of third ventricular NPY-elicited feeding following medullary reticular formation infusions of muscimol.

PubMed

Travers, Joseph B; Herman, Kenneth; Travers, Susan P

2010-04-01

The appetitive component of feeding is controlled by forebrain substrates, but the consummatory behaviors of licking, mastication, and swallowing are organized in the brainstem. The target of forebrain appetitive signals is unclear but likely includes regions of the medullary reticular formation (RF). This study was undertaken to determine the necessity of different RF regions for mastication induced by a descending appetitive signal. We measured solid food intake in response to third ventricular (3V) infusions of the orexigenic peptide neuropeptide Y 3-36 in awake, freely moving rats and determined whether focal RF infusions of the GABAA agonist muscimol suppressed eating. RF infusions were centered in either the lateral tegmental field, comprising the intermediate (IRt) and parvocellular (PCRt) RF, or in the nucleus gigantocellularis (Gi). Infusions of NPY 3-36 (5 microg/5 microl) into 3V significantly increased feeding of solid food over a 90-min period compared with the noninfused condition (4.3 g +/- 0.56 vs. 0.57 g +/- 0.57, p < .001). NPY 3-36-induced food intake was suppressed (1.7 g +/- 0.48) by simultaneous infusions of muscimol (0.6 mM/100 nl) into the IRt/PCRt (p < .01). Coincident with the decrease in feeding was a decrease in the amplitude of anterior digastric muscle contractions in response to intraoral sucrose infusions. In contrast, infusions of muscimol into Gi had no discernible effect on food intake or EMG amplitude. These data suggest that the IRt/PCRt is essential for forebrain-initiated mastication, but that the Gi is not a necessary link in this pathway.

Aerobic power and field test results of amateur 15-a-side rugby union players.

PubMed

Sant'anna, Ricardo T; de Souza Castro, Flávio A

2017-12-01

The aim of the present study was to verify whether it is possible to predict aerobic power in amateur 15-a-side rugby union players through the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IRT1) and the 5-meter Multiple Shuttle Test (5-m MST). Forty-two amateur players - 22 forwards and 20 backs - were evaluated in three phases: 1) maximum treadmill test in the laboratory; 2) field test set by a drawing in the first phase; and 3) second field test. Descriptive, comparison, correlation, regression and level of agreement analyses were performed. Backs, when compared to forwards, showed a higher VO2max (61.7±15 mL/kg/min and 51.6±10.1 mL/kg/min, respectively), Yo-Yo IRT1 final level (16.4±0.8 and 14.9±0.9, respectively) and Yo-Yo IRT1 total distance (1283.3±312.5 m and 792±277.6 m, respectively), and a higher final distance in the 5-m MST (686.8±36.6 and 642.9±46.5, respectively). Significant correlations were found between the result and the total distance on the Yo-Yo IRT1 and the VO2max (r=0.425 and r=0.459, respectively). Using the total distance covered in the Yo-Yo IRT1, the VO2max of amateur 15-a-side rugby union players can be estimated through the equation VO2max = 0.016 × (DIST Yo‑Yo) + 40.578. Yo-Yo IRT1 is most useful when the objective is to evaluate the aerobic power of amateur RU players in comparison with the 5-m MST.

The e-MSWS-12: improving the multiple sclerosis walking scale using item response theory.

PubMed

Engelhard, Matthew M; Schmidt, Karen M; Engel, Casey E; Brenton, J Nicholas; Patek, Stephen D; Goldman, Myla D

2016-12-01

The Multiple Sclerosis Walking Scale (MSWS-12) is the predominant patient-reported measure of multiple sclerosis (MS) -elated walking ability, yet it had not been analyzed using item response theory (IRT), the emerging standard for patient-reported outcome (PRO) validation. This study aims to reduce MSWS-12 measurement error and facilitate computerized adaptive testing by creating an IRT model of the MSWS-12 and distributing it online. MSWS-12 responses from 284 subjects with MS were collected by mail and used to fit and compare several IRT models. Following model selection and assessment, subpopulations based on age and sex were tested for differential item functioning (DIF). Model comparison favored a one-dimensional graded response model (GRM). This model met fit criteria and explained 87 % of response variance. The performance of each MSWS-12 item was characterized using category response curves (CRCs) and item information. IRT-based MSWS-12 scores correlated with traditional MSWS-12 scores (r = 0.99) and timed 25-foot walk (T25FW) speed (r =  -0.70). Item 2 showed DIF based on age (χ 2  = 19.02, df = 5, p < 0.01), and Item 11 showed DIF based on sex (χ 2  = 13.76, df = 5, p = 0.02). MSWS-12 measurement error depends on walking ability, but could be lowered by improving or replacing items with low information or DIF. The e-MSWS-12 includes IRT-based scoring, error checking, and an estimated T25FW derived from MSWS-12 responses. It is available at https://ms-irt.shinyapps.io/e-MSWS-12 .

Sci—Thur AM: YIS - 03: irtGPUMCD: a new GPU-calculated dosimetry code for {sup 177}Lu-octreotate radionuclide therapy of neuroendocrine tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montégiani, Jean-François; Gaudin, Émilie; Després, Philippe

2014-08-15

In peptide receptor radionuclide therapy (PRRT), huge inter-patient variability in absorbed radiation doses per administered activity mandates the utilization of individualized dosimetry to evaluate therapeutic efficacy and toxicity. We created a reliable GPU-calculated dosimetry code (irtGPUMCD) and assessed {sup 177}Lu-octreotate renal dosimetry in eight patients (4 cycles of approximately 7.4 GBq). irtGPUMCD was derived from a brachytherapy dosimetry code (bGPUMCD), which was adapted to {sup 177}Lu PRRT dosimetry. Serial quantitative single-photon emission computed tomography (SPECT) images were obtained from three SPECT/CT acquisitions performed at 4, 24 and 72 hours after {sup 177}Lu-octreotate administration, and registered with non-rigid deformation of CTmore » volumes, to obtain {sup 177}Lu-octreotate 4D quantitative biodistribution. Local energy deposition from the β disintegrations was assumed. Using Monte Carlo gamma photon transportation, irtGPUMCD computed dose rate at each time point. Average kidney absorbed dose was obtained from 1-cm{sup 3} VOI dose rate samples on each cortex, subjected to a biexponential curve fit. Integration of the latter time-dose rate curve yielded the renal absorbed dose. The mean renal dose per administered activity was 0.48 ± 0.13 Gy/GBq (range: 0.30–0.71 Gy/GBq). Comparison to another PRRT dosimetry code (VRAK: Voxelized Registration and Kinetics) showed fair accordance with irtGPUMCD (11.4 ± 6.8 %, range: 3.3–26.2%). These results suggest the possibility to use the irtGPUMCD code in order to personalize administered activity in PRRT. This could allow improving clinical outcomes by maximizing per-cycle tumor doses, without exceeding the tolerable renal dose.« less

Use of a Scale Model in the Design of Modifications to the NASA Glenn Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Canacci, Victor A.; Gonsalez, Jose C.; Spera, David A.; Burke, Thomas (Technical Monitor)

2001-01-01

Major modifications were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research tunnel (IRT) at the NASA Glenn Research Center, including replacement of its heat exchanger and associated ducts and turning vanes, and the addition of fan outlet guide vanes (OGV's). A one-tenth scale model of the IRT (designated as the SMIRT) was constructed with and without these modifications and tested to increase confidence in obtaining expected improvements in flow quality around the tunnel loop. The SMIRT is itself an aerodynamic test facility whose flow patterns without modifications have been shown to be accurate, scaled representations of those measured in the IRT prior to the 1999 upgrade program. In addition, tests in the SMIRT equipped with simulated OGV's indicated that these devices in the IRT might reduce flow distortions immediately downstream of the fan by two thirds. Flow quality parameters measured in the SMIRT were projected to the full-size modified IRT, and quantitative estimates of improvements in flow quality were given prior to construction. In this paper, the results of extensive flow quality studies conducted in the SMIRT are documented. Samples of these are then compared with equivalent measurements made in the full-scale IRT, both before and after its configuration was upgraded. Airspeed, turbulence intensity, and flow angularity distributions are presented for cross sections downstream of the drive fan, both upstream and downstream of the replacement flat heat exchanger, in the stilling chamber, in the test section, and in the wakes of the new comer turning vanes with their unique expanding and contracting designs. Lessons learned from these scale-model studies are discussed.

Response pattern of depressive symptoms among college students: What lies behind items of the Beck Depression Inventory-II?

PubMed

de Sá Junior, Antonio Reis; de Andrade, Arthur Guerra; Andrade, Laura Helena; Gorenstein, Clarice; Wang, Yuan-Pang

2018-07-01

This study examines the response pattern of depressive symptoms in a nationwide student sample, through item analyses of a rating scale by both classical test theory (CTT) and item response theory (IRT). The 21-item Beck Depression Inventory-II (BDI-II) was administered to 12,711 college students. First, the psychometric properties of the scale were described. Thereafter, the endorsement probability of depressive symptom in each scale item was analyzed through CTT and IRT. Graphical plots depicted the endorsement probability of scale items and intensity of depression. Three items of different difficulty level were compared through CTT and IRT approach. Four in five students reported the presence of depressive symptoms. The BDI-II items presented good reliability and were distributed along the symptomatic continuum of depression. Similarly, in both CTT and IRT approaches, the item 'changes in sleep' was easily endorsed, 'loss of interest' moderately and 'suicidal thoughts' hardly. Graphical representation of BDI-II of both methods showed much equivalence in terms of item discrimination and item difficulty. The item characteristic curve of the IRT method provided informative evaluation of item performance. The inventory was applied only in college students. Depressive symptoms were frequent psychopathological manifestations among college students. The performance of the BDI-II items indicated convergent results from both methods of analysis. While the CTT was easy to understand and to apply, the IRT was more complex to understand and to implement. Comprehensive assessment of the functioning of each BDI-II item might be helpful in efficient detection of depressive conditions in college students. Copyright © 2018 Elsevier B.V. All rights reserved.

Screening for cystic fibrosis in New York State: considerations for algorithm improvements.

PubMed

Kay, Denise M; Maloney, Breanne; Hamel, Rhonda; Pearce, Melissa; DeMartino, Lenore; McMahon, Rebecca; McGrath, Emily; Krein, Lea; Vogel, Beth; Saavedra-Matiz, Carlos A; Caggana, Michele; Tavakoli, Norma P

2016-02-01

Newborn screening for cystic fibrosis (CF), a chronic progressive disease affecting mucus viscosity, has been beneficial in both improving life expectancy and the quality of life for individuals with CF. In New York State from 2007 to 2012 screening for CF involved measuring immunoreactive trypsinogen (IRT) levels in dried blood spots from newborns using the IMMUCHEM(™) Blood Spot Trypsin-MW ELISA kit. Any specimen in the top 5% IRT level underwent DNA analysis using the InPlex(®) CF Molecular Test. Of the 1.48 million newborns screened during the 6-year time period, 7631 babies were referred for follow-up. CF was confirmed in 251 cases, and 94 cases were diagnosed with CF transmembrane conductance regulated-related metabolic syndrome or possible CF. Nine reports of false negatives were made to the program. Variation in daily average IRT was observed depending on the season (4-6 ng/ml) and kit lot (<3 ng/ml), supporting the use of a floating cutoff. The screening method had a sensitivity of 96.5%, specificity of 99.6%, positive predictive value of 4.5%, and negative predictive value of 99.5%. Considerations for CF screening algorithms should include IRT variations resulting from age at specimen collection, sex, race/ethnicity, season, and manufacturer kit lots. Measuring IRT level in dried blood spots is the first-tier screen for CF. Current algorithms for CF screening lead to substantial false-positive referral rates. IRT values were affected by age of infant when specimen is collected, race/ethnicity and sex of infant, and changes in seasons and manufacturer kit lots The prevalence of CF in NYS is 1 in 4200 with the highest prevalence in White infants (1 in 2600) and the lowest in Black infants (1 in 15,400).

Molecular Imaging and Therapy of Prostate Cancer

DTIC Science & Technology

2015-10-01

arsenic-based, IGF1R-targeted radiopharmaceuticals can allow for PET imaging, IRT, and monitoring the therapeutic response of PCa. Specific Aims: Aim 1: To...models with PET imaging. Aim 3: To monitor the efficacy of 76As-based IRT of PCa with multimodality imaging.

Model Selection Methods for Mixture Dichotomous IRT Models

ERIC Educational Resources Information Center

Li, Feiming; Cohen, Allan S.; Kim, Seock-Ho; Cho, Sun-Joo

2009-01-01

This study examines model selection indices for use with dichotomous mixture item response theory (IRT) models. Five indices are considered: Akaike's information coefficient (AIC), Bayesian information coefficient (BIC), deviance information coefficient (DIC), pseudo-Bayes factor (PsBF), and posterior predictive model checks (PPMC). The five…

An Introduction to Item Response Theory for Patient-Reported Outcome Measurement

PubMed Central

Nguyen, Tam H.; Han, Hae-Ra; Kim, Miyong T.

2015-01-01

The growing emphasis on patient-centered care has accelerated the demand for high-quality data from patient-reported outcome (PRO) measures. Traditionally, the development and validation of these measures has been guided by classical test theory. However, item response theory (IRT), an alternate measurement framework, offers promise for addressing practical measurement problems found in health-related research that have been difficult to solve through classical methods. This paper introduces foundational concepts in IRT, as well as commonly used models and their assumptions. Existing data on a combined sample (n = 636) of Korean American and Vietnamese American adults who responded to the High Blood Pressure Health Literacy Scale and the Patient Health Questionnaire-9 are used to exemplify typical applications of IRT. These examples illustrate how IRT can be used to improve the development, refinement, and evaluation of PRO measures. Greater use of methods based on this framework can increase the accuracy and efficiency with which PROs are measured. PMID:24403095

Assessing item fit for unidimensional item response theory models using residuals from estimated item response functions.

PubMed

Haberman, Shelby J; Sinharay, Sandip; Chon, Kyong Hee

2013-07-01

Residual analysis (e.g. Hambleton & Swaminathan, Item response theory: principles and applications, Kluwer Academic, Boston, 1985; Hambleton, Swaminathan, & Rogers, Fundamentals of item response theory, Sage, Newbury Park, 1991) is a popular method to assess fit of item response theory (IRT) models. We suggest a form of residual analysis that may be applied to assess item fit for unidimensional IRT models. The residual analysis consists of a comparison of the maximum-likelihood estimate of the item characteristic curve with an alternative ratio estimate of the item characteristic curve. The large sample distribution of the residual is proved to be standardized normal when the IRT model fits the data. We compare the performance of our suggested residual to the standardized residual of Hambleton et al. (Fundamentals of item response theory, Sage, Newbury Park, 1991) in a detailed simulation study. We then calculate our suggested residuals using data from an operational test. The residuals appear to be useful in assessing the item fit for unidimensional IRT models.

A Zero- and K-Inflated Mixture Model for Health Questionnaire Data

PubMed Central

Finkelman, Matthew D.; Green, Jennifer Greif; Gruber, Michael J.; Zaslavsky, Alan M.

2011-01-01

In psychiatric assessment, Item Response Theory (IRT) is a popular tool to formalize the relation between the severity of a disorder and associated responses to questionnaire items. Practitioners of IRT sometimes make the assumption of normally distributed severities within a population; while convenient, this assumption is often violated when measuring psychiatric disorders. Specifically, there may be a sizable group of respondents whose answers place them at an extreme of the latent trait spectrum. In this article, a zero- and K-inflated mixture model is developed to account for the presence of such respondents. The model is fitted using an expectation-maximization (E-M) algorithm to estimate the percentage of the population at each end of the continuum, concurrently analyzing the remaining “graded component” via IRT. A method to perform factor analysis for only the graded component is introduced. In assessments of oppositional defiant disorder and conduct disorder, the zero- and K-inflated model exhibited better fit than the standard IRT model. PMID:21365673

An introduction to item response theory for patient-reported outcome measurement.

PubMed

Nguyen, Tam H; Han, Hae-Ra; Kim, Miyong T; Chan, Kitty S

2014-01-01

The growing emphasis on patient-centered care has accelerated the demand for high-quality data from patient-reported outcome (PRO) measures. Traditionally, the development and validation of these measures has been guided by classical test theory. However, item response theory (IRT), an alternate measurement framework, offers promise for addressing practical measurement problems found in health-related research that have been difficult to solve through classical methods. This paper introduces foundational concepts in IRT, as well as commonly used models and their assumptions. Existing data on a combined sample (n = 636) of Korean American and Vietnamese American adults who responded to the High Blood Pressure Health Literacy Scale and the Patient Health Questionnaire-9 are used to exemplify typical applications of IRT. These examples illustrate how IRT can be used to improve the development, refinement, and evaluation of PRO measures. Greater use of methods based on this framework can increase the accuracy and efficiency with which PROs are measured.

How States Can Reduce the Dropout Rate for Undocumented Immigrant Youth: The Effects of In-State Resident Tuition Policies

PubMed Central

Potochnick, Stephanie

2016-01-01

As of December 2011, 13 states have adopted an in-state resident tuition (IRT) policy that provides in-state tuition to undocumented immigrants and several other states are considering similar legislation. While previous research focuses on how IRT policies affect college entry and attainment, this study examines the effect these policies have on high school dropout behavior. Using the Current Population Survey (CPS) and difference-in-difference models, this paper examines whether IRT policies reduce the likelihood of dropping out of high school for Mexican foreign-born non-citizens (FBNC), a proxy for undocumented youth. The policy is estimated to cause an eight percentage point reduction in the proportion that drops out of high school. The paper develops an integrated framework that combines human capital theory with segmented assimilation theory to provide insight into how IRT policies influence student motivation and educational attainment at the high school level. PMID:24576624

Ground and surface temperature variability for remote sensing of soil moisture in a heterogeneous landscape

USGS Publications Warehouse

Giraldo, M.A.; Bosch, D.; Madden, M.; Usery, L.; Finn, M.

2009-01-01

At the Little River Watershed (LRW) heterogeneous landscape near Tifton Georgia US an in situ network of stations operated by the US Department of Agriculture-Agriculture Research Service-Southeast Watershed Research Lab (USDA-ARS-SEWRL) was established in 2003 for the long term study of climatic and soil biophysical processes. To develop an accurate interpolation of the in situ readings that can be used to produce distributed representations of soil moisture (SM) and energy balances at the landscape scale for remote sensing studies, we studied (1) the temporal and spatial variations of ground temperature (GT) and infra red temperature (IRT) within 30 by 30 m plots around selected network stations; (2) the relationship between the readings from the eight 30 by 30 m plots and the point reading of the network stations for the variables SM, GT and IRT; and (3) the spatial and temporal variation of GT and IRT within agriculture landuses: grass, orchard, peanuts, cotton and bare soil in the surrounding landscape. The results showed high correlations between the station readings and the adjacent 30 by 30 m plot average value for SM; high seasonal independent variation in the GT and IRT behavior among the eight 30 by 30 m plots; and site specific, in-field homogeneity in each 30 by 30 m plot. We found statistical differences in the GT and IRT between the different landuses as well as high correlations between GT and IRT regardless of the landuse. Greater standard deviations for IRT than for GT (in the range of 2-4) were found within the 30 by 30 m, suggesting that when a single point reading for this variable is selected for the validation of either remote sensing data or water-energy models, errors may occur. The results confirmed that in this landscape homogeneous 30 by 30 m plots can be used as landscape spatial units for soil moisture and ground temperature studies. Under this landscape conditions small plots can account for local expressions of environmental processes, decreasing the errors and uncertainties in remote sensing estimates caused by landscape heterogeneity.

Inhibitor-resistant TEM- and OXA-1-producing Escherichia coli isolates resistant to amoxicillin-clavulanate are more clonal and possess lower virulence gene content than susceptible clinical isolates.

PubMed

Oteo, Jesús; González-López, Juan José; Ortega, Adriana; Quintero-Zárate, J Natalia; Bou, Germán; Cercenado, Emilia; Conejo, María Carmen; Martínez-Martínez, Luis; Navarro, Ferran; Oliver, Antonio; Bartolomé, Rosa M; Campos, José

2014-07-01

In a previous prospective multicenter study in Spain, we found that OXA-1 and inhibitor-resistant TEM (IRT) β-lactamases constitute the most common plasmid-borne mechanisms of genuine amoxicillin-clavulanate (AMC) resistance in Escherichia coli. In the present study, we investigated the population structure and virulence traits of clinical AMC-resistant E. coli strains expressing OXA-1 or IRT and compared these traits to those in a control group of clinical AMC-susceptible E. coli isolates. All OXA-1-producing (n = 67) and IRT-producing (n = 45) isolates were matched by geographical and temporal origin to the AMC-susceptible control set (n = 56). We performed multilocus sequence typing and phylogenetic group characterization for each isolate and then studied the isolates for the presence of 49 virulence factors (VFs) by PCR and sequencing. The most prevalent clone detected was distinct for each group: group C isolates of sequence type (ST) 88 (C/ST88) were the most common in OXA-1 producers, B2/ST131 isolates were the most common in IRT producers, and B2/ST73 isolates were the most common in AMC-susceptible isolates. The median numbers of isolates per ST were 3.72 in OXA-1 producers, 2.04 in IRT producers, and 1.69 in AMC-susceptible isolates; the proportions of STs represented by one unique isolate in each group were 19.4%, 31.1%, and 48.2%, respectively. The sum of all VFs detected, calculated as a virulence score, was significantly higher in AMC-susceptible isolates than OXA-1 and IRT producers (means, 12.5 versus 8.3 and 8.2, respectively). Our findings suggest that IRT- and OXA-1-producing E. coli isolates resistant to AMC have a different and less diverse population structure than AMC-susceptible clinical E. coli isolates. The AMC-susceptible population also contains more VFs than AMC-resistant isolates. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Estimating the Nominal Response Model under Nonnormal Conditions

ERIC Educational Resources Information Center

Preston, Kathleen Suzanne Johnson; Reise, Steven Paul

2014-01-01

The nominal response model (NRM), a much understudied polytomous item response theory (IRT) model, provides researchers the unique opportunity to evaluate within-item category distinctions. Polytomous IRT models, such as the NRM, are frequently applied to psychological assessments representing constructs that are unlikely to be normally…

An Instructional Module on Mokken Scale Analysis

ERIC Educational Resources Information Center

Wind, Stefanie A.

2017-01-01

Mokken scale analysis (MSA) is a probabilistic-nonparametric approach to item response theory (IRT) that can be used to evaluate fundamental measurement properties with less strict assumptions than parametric IRT models. This instructional module provides an introduction to MSA as a probabilistic-nonparametric framework in which to explore…

Comparing Three Estimation Methods for the Three-Parameter Logistic IRT Model

ERIC Educational Resources Information Center

Lamsal, Sunil

2015-01-01

Different estimation procedures have been developed for the unidimensional three-parameter item response theory (IRT) model. These techniques include the marginal maximum likelihood estimation, the fully Bayesian estimation using Markov chain Monte Carlo simulation techniques, and the Metropolis-Hastings Robbin-Monro estimation. With each…

A novel method for expediting the development of patient-reported outcome measures and an evaluation across several populations

PubMed Central

Garrard, Lili; Price, Larry R.; Bott, Marjorie J.; Gajewski, Byron J.

2016-01-01

Item response theory (IRT) models provide an appropriate alternative to the classical ordinal confirmatory factor analysis (CFA) during the development of patient-reported outcome measures (PROMs). Current literature has identified the assessment of IRT model fit as both challenging and underdeveloped (Sinharay & Johnson, 2003; Sinharay, Johnson, & Stern, 2006). This study evaluates the performance of Ordinal Bayesian Instrument Development (OBID), a Bayesian IRT model with a probit link function approach, through applications in two breast cancer-related instrument development studies. The primary focus is to investigate an appropriate method for comparing Bayesian IRT models in PROMs development. An exact Bayesian leave-one-out cross-validation (LOO-CV) approach (Vehtari & Lampinen, 2002) is implemented to assess prior selection for the item discrimination parameter in the IRT model and subject content experts’ bias (in a statistical sense and not to be confused with psychometric bias as in differential item functioning) toward the estimation of item-to-domain correlations. Results support the utilization of content subject experts’ information in establishing evidence for construct validity when sample size is small. However, the incorporation of subject experts’ content information in the OBID approach can be sensitive to the level of expertise of the recruited experts. More stringent efforts need to be invested in the appropriate selection of subject experts to efficiently use the OBID approach and reduce potential bias during PROMs development. PMID:27667878

A novel method for expediting the development of patient-reported outcome measures and an evaluation across several populations.

PubMed

Garrard, Lili; Price, Larry R; Bott, Marjorie J; Gajewski, Byron J

2016-10-01

Item response theory (IRT) models provide an appropriate alternative to the classical ordinal confirmatory factor analysis (CFA) during the development of patient-reported outcome measures (PROMs). Current literature has identified the assessment of IRT model fit as both challenging and underdeveloped (Sinharay & Johnson, 2003; Sinharay, Johnson, & Stern, 2006). This study evaluates the performance of Ordinal Bayesian Instrument Development (OBID), a Bayesian IRT model with a probit link function approach, through applications in two breast cancer-related instrument development studies. The primary focus is to investigate an appropriate method for comparing Bayesian IRT models in PROMs development. An exact Bayesian leave-one-out cross-validation (LOO-CV) approach (Vehtari & Lampinen, 2002) is implemented to assess prior selection for the item discrimination parameter in the IRT model and subject content experts' bias (in a statistical sense and not to be confused with psychometric bias as in differential item functioning) toward the estimation of item-to-domain correlations. Results support the utilization of content subject experts' information in establishing evidence for construct validity when sample size is small. However, the incorporation of subject experts' content information in the OBID approach can be sensitive to the level of expertise of the recruited experts. More stringent efforts need to be invested in the appropriate selection of subject experts to efficiently use the OBID approach and reduce potential bias during PROMs development.

Recent use of medical infrared thermography in skin neoplasms.

PubMed

Magalhaes, C; Vardasca, R; Mendes, J

2018-03-25

Infrared thermal imaging captures the infrared radiation emitted by the skin surface. The thermograms contain valuable information, since the temperature distribution can be used to characterize physiological anomalies. Thus, the use of infrared thermal imaging (IRT) has been studied as a possible medical tool to aid in the diagnosis of skin oncological lesions. The aim of this review is to assess the current state of the applications of IRT in skin neoplasm identification and characterization. A literature survey was conducted using the reference bibliographic databases: Scopus, PubMed and ISI Web of Science. Keywords (thermography, infrared imaging, thermal imaging and skin cancer) were combined and its presence was verified at the title and abstract of the article or as a main topic. Only articles published after 2013 were considered during this search. In total, 55 articles were encountered, resulting in 14 publications for revision after applying the exclusion criteria. It was denoted that IRT have been used to characterize and distinguish between malignant and benign neoplasms and different skin cancer types. IRT has also been successfully applied in the treatment evaluation of these types of lesions. Trends and future challenges have been established to improve the application of IRT in this field, disclosing that dynamic thermography is a promising tool for early identification of oncological skin conditions. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Specific and social fears in children and adolescents: separating normative fears from problem indicators and phobias.

PubMed

Laporte, Paola P; Pan, Pedro M; Hoffmann, Mauricio S; Wakschlag, Lauren S; Rohde, Luis A; Miguel, Euripedes C; Pine, Daniel S; Manfro, Gisele G; Salum, Giovanni A

2017-01-01

To distinguish normative fears from problematic fears and phobias. We investigated 2,512 children and adolescents from a large community school-based study, the High Risk Study for Psychiatric Disorders. Parent reports of 18 fears and psychiatric diagnosis were investigated. We used two analytical approaches: confirmatory factor analysis (CFA)/item response theory (IRT) and nonparametric receiver operating characteristic (ROC) curve. According to IRT and ROC analyses, social fears are more likely to indicate problems and phobias than specific fears. Most specific fears were normative when mild; all specific fears indicate problems when pervasive. In addition, the situational fear of toilets and people who look unusual were highly indicative of specific phobia. Among social fears, those not restricted to performance and fear of writing in front of others indicate problems when mild. All social fears indicate problems and are highly indicative of social phobia when pervasive. These preliminary findings provide guidance for clinicians and researchers to determine the boundaries that separate normative fears from problem indicators in children and adolescents, and indicate a differential severity threshold for specific and social fears.

Evaluating Equating Accuracy and Assumptions for Groups that Differ in Performance

ERIC Educational Resources Information Center

Powers, Sonya; Kolen, Michael J.

2014-01-01

Accurate equating results are essential when comparing examinee scores across exam forms. Previous research indicates that equating results may not be accurate when group differences are large. This study compared the equating results of frequency estimation, chained equipercentile, item response theory (IRT) true-score, and IRT observed-score…

Detecting Local Item Dependence in Polytomous Adaptive Data

ERIC Educational Resources Information Center

Mislevy, Jessica L.; Rupp, Andre A.; Harring, Jeffrey R.

2012-01-01

A rapidly expanding arena for item response theory (IRT) is in attitudinal and health-outcomes survey applications, often with polytomous items. In particular, there is interest in computer adaptive testing (CAT). Meeting model assumptions is necessary to realize the benefits of IRT in this setting, however. Although initial investigations of…

Rasch Analysis for Binary Data with Nonignorable Nonresponses

ERIC Educational Resources Information Center

Bertoli-Barsotti, Lucio; Punzo, Antonio

2013-01-01

This paper introduces a two-dimensional Item Response Theory (IRT) model to deal with nonignorable nonresponses in tests with dichotomous items. One dimension provides information about the omitting behavior, while the other dimension is related to the person's "ability". The idea of embedding an IRT model for missingness into the measurement…

Estimating a Noncompensatory IRT Model Using Metropolis within Gibbs Sampling

ERIC Educational Resources Information Center

Babcock, Ben

2011-01-01

Relatively little research has been conducted with the noncompensatory class of multidimensional item response theory (MIRT) models. A Monte Carlo simulation study was conducted exploring the estimation of a two-parameter noncompensatory item response theory (IRT) model. The estimation method used was a Metropolis-Hastings within Gibbs algorithm…

Practical Guide to Conducting an Item Response Theory Analysis

ERIC Educational Resources Information Center

Toland, Michael D.

2014-01-01

Item response theory (IRT) is a psychometric technique used in the development, evaluation, improvement, and scoring of multi-item scales. This pedagogical article provides the necessary information needed to understand how to conduct, interpret, and report results from two commonly used ordered polytomous IRT models (Samejima's graded…

IRT Item Parameter Recovery with Marginal Maximum Likelihood Estimation Using Loglinear Smoothing Models

ERIC Educational Resources Information Center

Casabianca, Jodi M.; Lewis, Charles

2015-01-01

Loglinear smoothing (LLS) estimates the latent trait distribution while making fewer assumptions about its form and maintaining parsimony, thus leading to more precise item response theory (IRT) item parameter estimates than standard marginal maximum likelihood (MML). This article provides the expectation-maximization algorithm for MML estimation…

Adaptive Testing without IRT.

ERIC Educational Resources Information Center

Yan, Duanli; Lewis, Charles; Stocking, Martha

It is unrealistic to suppose that standard item response theory (IRT) models will be appropriate for all new and currently considered computer-based tests. In addition to developing new models, researchers will need to give some attention to the possibility of constructing and analyzing new tests without the aid of strong models. Computerized…

Stochastic Ordering Using the Latent Trait and the Sum Score in Polytomous IRT Models.

ERIC Educational Resources Information Center

Hemker, Bas T.; Sijtsma, Klaas; Molenaar, Ivo W.; Junker, Brian W.

1997-01-01

Stochastic ordering properties are investigated for a broad class of item response theory (IRT) models for which the monotone likelihood ratio does not hold. A taxonomy is given for nonparametric and parametric models for polytomous models based on the hierarchical relationship between the models. (SLD)

Likelihood-Ratio DIF Testing: Effects of Nonnormality

ERIC Educational Resources Information Center

Woods, Carol M.

2008-01-01

Differential item functioning (DIF) occurs when an item has different measurement properties for members of one group versus another. Likelihood-ratio (LR) tests for DIF based on item response theory (IRT) involve statistically comparing IRT models that vary with respect to their constraints. A simulation study evaluated how violation of the…

IRT-Estimated Reliability for Tests Containing Mixed Item Formats

ERIC Educational Resources Information Center

Shu, Lianghua; Schwarz, Richard D.

2014-01-01

As a global measure of precision, item response theory (IRT) estimated reliability is derived for four coefficients (Cronbach's a, Feldt-Raju, stratified a, and marginal reliability). Models with different underlying assumptions concerning test-part similarity are discussed. A detailed computational example is presented for the targeted…

Modelling Mathematics Problem Solving Item Responses Using a Multidimensional IRT Model

ERIC Educational Resources Information Center

Wu, Margaret; Adams, Raymond

2006-01-01

This research examined students' responses to mathematics problem-solving tasks and applied a general multidimensional IRT model at the response category level. In doing so, cognitive processes were identified and modelled through item response modelling to extract more information than would be provided using conventional practices in scoring…

Model Selection Indices for Polytomous Items

ERIC Educational Resources Information Center

Kang, Taehoon; Cohen, Allan S.; Sung, Hyun-Jung

2009-01-01

This study examines the utility of four indices for use in model selection with nested and nonnested polytomous item response theory (IRT) models: a cross-validation index and three information-based indices. Four commonly used polytomous IRT models are considered: the graded response model, the generalized partial credit model, the partial credit…

Assessing Equating Results on Different Equating Criteria

ERIC Educational Resources Information Center

Tong, Ye; Kolen, Michael

2005-01-01

The performance of three equating methods--the presmoothed equipercentile method, the item response theory (IRT) true score method, and the IRT observed score method--were examined based on three equating criteria: the same distributions property, the first-order equity property, and the second-order equity property. The magnitude of the…

Bayesian Estimation of Multi-Unidimensional Graded Response IRT Models

ERIC Educational Resources Information Center

Kuo, Tzu-Chun

2015-01-01

Item response theory (IRT) has gained an increasing popularity in large-scale educational and psychological testing situations because of its theoretical advantages over classical test theory. Unidimensional graded response models (GRMs) are useful when polytomous response items are designed to measure a unified latent trait. They are limited in…

On the Bayesian Nonparametric Generalization of IRT-Type Models

ERIC Educational Resources Information Center

San Martin, Ernesto; Jara, Alejandro; Rolin, Jean-Marie; Mouchart, Michel

2011-01-01

We study the identification and consistency of Bayesian semiparametric IRT-type models, where the uncertainty on the abilities' distribution is modeled using a prior distribution on the space of probability measures. We show that for the semiparametric Rasch Poisson counts model, simple restrictions ensure the identification of a general…

Invariance Properties for General Diagnostic Classification Models

ERIC Educational Resources Information Center

Bradshaw, Laine P.; Madison, Matthew J.

2016-01-01

In item response theory (IRT), the invariance property states that item parameter estimates are independent of the examinee sample, and examinee ability estimates are independent of the test items. While this property has long been established and understood by the measurement community for IRT models, the same cannot be said for diagnostic…

Unidimensional Interpretations for Multidimensional Test Items

ERIC Educational Resources Information Center

Kahraman, Nilufer

2013-01-01

This article considers potential problems that can arise in estimating a unidimensional item response theory (IRT) model when some test items are multidimensional (i.e., show a complex factorial structure). More specifically, this study examines (1) the consequences of model misfit on IRT item parameter estimates due to unintended minor item-level…

IRTs of the ABCs: Children's Letter Name Acquisition

ERIC Educational Resources Information Center

Phillips, Beth M.; Piasta, Shayne B.; Anthony, Jason L.; Lonigan, Christopher J.; Francis, David J.

2012-01-01

We examined the developmental sequence of letter name knowledge acquisition by children from 2 to five years of age. Data from 2 samples representing diverse regions, ethnicity, and socioeconomic backgrounds (ns=1074 and 500) were analyzed using item response theory (IRT) and differential item functioning techniques. Results from factor analyses…

The Performance of IRT Model Selection Methods with Mixed-Format Tests

ERIC Educational Resources Information Center

Whittaker, Tiffany A.; Chang, Wanchen; Dodd, Barbara G.

2012-01-01

When tests consist of multiple-choice and constructed-response items, researchers are confronted with the question of which item response theory (IRT) model combination will appropriately represent the data collected from these mixed-format tests. This simulation study examined the performance of six model selection criteria, including the…

Genomic signatures of adaptation to wine biological ageing conditions in biofilm-forming flor yeasts.

PubMed

Coi, A L; Bigey, F; Mallet, S; Marsit, S; Zara, G; Gladieux, P; Galeote, V; Budroni, M; Dequin, S; Legras, J L

2017-04-01

The molecular and evolutionary processes underlying fungal domestication remain largely unknown despite the importance of fungi to bioindustry and for comparative adaptation genomics in eukaryotes. Wine fermentation and biological ageing are performed by strains of S. cerevisiae with, respectively, pelagic fermentative growth on glucose and biofilm aerobic growth utilizing ethanol. Here, we use environmental samples of wine and flor yeasts to investigate the genomic basis of yeast adaptation to contrasted anthropogenic environments. Phylogenetic inference and population structure analysis based on single nucleotide polymorphisms revealed a group of flor yeasts separated from wine yeasts. A combination of methods revealed several highly differentiated regions between wine and flor yeasts, and analyses using codon-substitution models for detecting molecular adaptation identified sites under positive selection in the high-affinity transporter gene ZRT1. The cross-population composite likelihood ratio revealed selective sweeps at three regions, including in the hexose transporter gene HXT7, the yapsin gene YPS6 and the membrane protein coding gene MTS27. Our analyses also revealed that the biological ageing environment has led to the accumulation of numerous mutations in proteins from several networks, including Flo11 regulation and divalent metal transport. Together, our findings suggest that the tuning of FLO11 expression and zinc transport networks are a distinctive feature of the genetic changes underlying the domestication of flor yeasts. Our study highlights the multiplicity of genomic changes underlying yeast adaptation to man-made habitats and reveals that flor/wine yeast lineage can serve as a useful model for studying the genomics of adaptive divergence. © 2017 John Wiley & Sons Ltd.

Assessment of a Technique for Estimating Total Column Water Vapor Using Measurements of the Infrared Sky Temperature

NASA Technical Reports Server (NTRS)

Merceret, Francis J.; Huddleston, Lisa L.

2014-01-01

A method for estimating the integrated precipitable water (IPW) content of the atmosphere using measurements of indicated infrared zenith sky temperature was validated over east-central Florida. The method uses inexpensive, commercial off the shelf, hand-held infrared thermometers (IRT). Two such IRTs were obtained from a commercial vendor, calibrated against several laboratory reference sources at KSC, and used to make IR zenith sky temperature measurements in the vicinity of KSC and Cape Canaveral Air Force Station (CCAFS). The calibration and comparison data showed that these inexpensive IRTs provided reliable, stable IR temperature measurements that were well correlated with the NOAA IPW observations.

Flow Quality Measurements in an Aerodynamic Model of NASA Lewis' Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Canacci, Victor A.; Gonsalez, Jose C.

1999-01-01

As part of an ongoing effort to improve the aerodynamic flow characteristics of the Icing Research Tunnel (IRT), a modular scale model of the facility was fabricated. This 1/10th-scale model was used to gain further understanding of the flow characteristics in the IRT. The model was outfitted with instrumentation and data acquisition systems to determine pressures, velocities, and flow angles in the settling chamber and test section. Parametric flow quality studies involving the insertion and removal of a model of the IRT's distinctive heat exchanger (cooler) and/or of a honeycomb in the settling chamber were performed. These experiments illustrate the resulting improvement or degradation in flow quality.

Goodness of Model-Data Fit and Invariant Measurement

ERIC Educational Resources Information Center

Engelhard, George, Jr.; Perkins, Aminah

2013-01-01

In this commentary, Englehard and Perkins remark that Maydeu-Olivares has presented a framework for evaluating the goodness of model-data fit for item response theory (IRT) models and correctly points out that overall goodness-of-fit evaluations of IRT models and data are not generally explored within most applications in educational and…

Statistical Indexes for Monitoring Item Behavior under Computer Adaptive Testing Environment.

ERIC Educational Resources Information Center

Zhu, Renbang; Yu, Feng; Liu, Su

A computerized adaptive test (CAT) administration usually requires a large supply of items with accurately estimated psychometric properties, such as item response theory (IRT) parameter estimates, to ensure the precision of examinee ability estimation. However, an estimated IRT model of a given item in any given pool does not always correctly…

Optimal Item Selection with Credentialing Examinations.

ERIC Educational Resources Information Center

Hambleton, Ronald K.; And Others

The study compared two promising item response theory (IRT) item-selection methods, optimal and content-optimal, with two non-IRT item selection methods, random and classical, for use in fixed-length certification exams. The four methods were used to construct 20-item exams from a pool of approximately 250 items taken from a 1985 certification…

The Effect of Year-to-Year Rater Variation on IRT Linking

ERIC Educational Resources Information Center

Yen, Shu Jing; Ochieng, Charles; Michaels, Hillary; Friedman, Greg

2005-01-01

Year-to-year rater variation may result in constructed response (CR) parameter changes, making CR items inappropriate to use in anchor sets for linking or equating. This study demonstrates how rater severity affected the writing and reading scores. Rater adjustments were made to statewide results using an item response theory (IRT) methodology…

Obstacles to Developing Digital Literacy on the Internet in Middle School Science Instruction

ERIC Educational Resources Information Center

Colwell, Jamie; Hunt-Barron, Sarah; Reinking, David

2013-01-01

Obstacles, and instructional responses to them, that emerged in two middle school science classes during a formative experiment investigating Internet Reciprocal Teaching (IRT), an instructional intervention aimed at increasing digital literacy on the Internet, are reported in this manuscript. Analysis of qualitative data revealed that IRT enabled…

An Extension of IRT-Based Equating to the Dichotomous Testlet Response Theory Model

ERIC Educational Resources Information Center

Tao, Wei; Cao, Yi

2016-01-01

Current procedures for equating number-correct scores using traditional item response theory (IRT) methods assume local independence. However, when tests are constructed using testlets, one concern is the violation of the local item independence assumption. The testlet response theory (TRT) model is one way to accommodate local item dependence.…

Preequating with Empirical Item Characteristic Curves: An Observed-Score Preequating Method

ERIC Educational Resources Information Center

Zu, Jiyun; Puhan, Gautam

2014-01-01

Preequating is in demand because it reduces score reporting time. In this article, we evaluated an observed-score preequating method: the empirical item characteristic curve (EICC) method, which makes preequating without item response theory (IRT) possible. EICC preequating results were compared with a criterion equating and with IRT true-score…

An Alternative Methodology for Creating Parallel Test Forms Using the IRT Information Function.

ERIC Educational Resources Information Center

Ackerman, Terry A.

The purpose of this paper is to report results on the development of a new computer-assisted methodology for creating parallel test forms using the item response theory (IRT) information function. Recently, several researchers have approached test construction from a mathematical programming perspective. However, these procedures require…

Extended Mixed-Efects Item Response Models with the MH-RM Algorithm

ERIC Educational Resources Information Center

Chalmers, R. Philip

2015-01-01

A mixed-effects item response theory (IRT) model is presented as a logical extension of the generalized linear mixed-effects modeling approach to formulating explanatory IRT models. Fixed and random coefficients in the extended model are estimated using a Metropolis-Hastings Robbins-Monro (MH-RM) stochastic imputation algorithm to accommodate for…

Distinguishing Continuous and Discrete Approaches to Multilevel Mixture IRT Models: A Model Comparison Perspective

ERIC Educational Resources Information Center

Zhu, Xiaoshu

2013-01-01

The current study introduced a general modeling framework, multilevel mixture IRT (MMIRT) which detects and describes characteristics of population heterogeneity, while accommodating the hierarchical data structure. In addition to introducing both continuous and discrete approaches to MMIRT, the main focus of the current study was to distinguish…

Comparison of IRT Likelihood Ratio Test and Logistic Regression DIF Detection Procedures

ERIC Educational Resources Information Center

Atar, Burcu; Kamata, Akihito

2011-01-01

The Type I error rates and the power of IRT likelihood ratio test and cumulative logit ordinal logistic regression procedures in detecting differential item functioning (DIF) for polytomously scored items were investigated in this Monte Carlo simulation study. For this purpose, 54 simulation conditions (combinations of 3 sample sizes, 2 sample…

The Robustness of IRT-Based Vertical Scaling Methods to Violation of Unidimensionality

ERIC Educational Resources Information Center

Yin, Liqun

2013-01-01

In recent years, many states have adopted Item Response Theory (IRT) based vertically scaled tests due to their compelling features in a growth-based accountability context. However, selection of a practical and effective calibration/scaling method and proper understanding of issues with possible multidimensionality in the test data is critical to…

Using Item Response Theory and Adaptive Testing in Online Career Assessment

ERIC Educational Resources Information Center

Betz, Nancy E.; Turner, Brandon M.

2011-01-01

The present article describes the potential utility of item response theory (IRT) and adaptive testing for scale evaluation and for web-based career assessment. The article describes the principles of both IRT and adaptive testing and then illustrates these with reference to data analyses and simulation studies of the Career Confidence Inventory…

Applying Kaplan-Meier to Item Response Data

ERIC Educational Resources Information Center

McNeish, Daniel

2018-01-01

Some IRT models can be equivalently modeled in alternative frameworks such as logistic regression. Logistic regression can also model time-to-event data, which concerns the probability of an event occurring over time. Using the relation between time-to-event models and logistic regression and the relation between logistic regression and IRT, this…

Five Methods for Estimating Angoff Cut Scores with IRT

ERIC Educational Resources Information Center

Wyse, Adam E.

2017-01-01

This article illustrates five different methods for estimating Angoff cut scores using item response theory (IRT) models. These include maximum likelihood (ML), expected a priori (EAP), modal a priori (MAP), and weighted maximum likelihood (WML) estimators, as well as the most commonly used approach based on translating ratings through the test…

Exploring Unidimensional Proficiency Classification Accuracy from Multidimensional Data in a Vertical Scaling Context

ERIC Educational Resources Information Center

Kroopnick, Marc Howard

2010-01-01

When Item Response Theory (IRT) is operationally applied for large scale assessments, unidimensionality is typically assumed. This assumption requires that the test measures a single latent trait. Furthermore, when tests are vertically scaled using IRT, the assumption of unidimensionality would require that the battery of tests across grades…

Bayesian Estimation of the Logistic Positive Exponent IRT Model

ERIC Educational Resources Information Center

Bolfarine, Heleno; Bazan, Jorge Luis

2010-01-01

A Bayesian inference approach using Markov Chain Monte Carlo (MCMC) is developed for the logistic positive exponent (LPE) model proposed by Samejima and for a new skewed Logistic Item Response Theory (IRT) model, named Reflection LPE model. Both models lead to asymmetric item characteristic curves (ICC) and can be appropriate because a symmetric…

Unidimensional and Multidimensional Models for Item Response Theory.

ERIC Educational Resources Information Center

McDonald, Roderick P.

This paper provides an up-to-date review of the relationship between item response theory (IRT) and (nonlinear) common factor theory and draws out of this relationship some implications for current and future research in IRT. Nonlinear common factor analysis yields a natural embodiment of the weak principle of local independence in appropriate…

Random Item IRT Models

ERIC Educational Resources Information Center

De Boeck, Paul

2008-01-01

It is common practice in IRT to consider items as fixed and persons as random. Both, continuous and categorical person parameters are most often random variables, whereas for items only continuous parameters are used and they are commonly of the fixed type, although exceptions occur. It is shown in the present article that random item parameters…

Finite Mixture Multilevel Multidimensional Ordinal IRT Models for Large Scale Cross-Cultural Research

ERIC Educational Resources Information Center

de Jong, Martijn G.; Steenkamp, Jan-Benedict E. M.

2010-01-01

We present a class of finite mixture multilevel multidimensional ordinal IRT models for large scale cross-cultural research. Our model is proposed for confirmatory research settings. Our prior for item parameters is a mixture distribution to accommodate situations where different groups of countries have different measurement operations, while…

The Information Function for the One-Parameter Logistic Model: Is it Reliability?

ERIC Educational Resources Information Center

Doran, Harold C.

2005-01-01

The information function is an important statistic in item response theory (IRT) applications. Although the information function is often described as the IRT version of reliability, it differs from the classical notion of reliability from a critical perspective: replication. This article first explores the information function for the…

Risky Business: Understanding Student Intellectual Risk Taking in Management Education

ERIC Educational Resources Information Center

Dachner, Alison M.; Miguel, Rosanna F.; Patena, Rachel A.

2017-01-01

The demands of today's ever-changing work environment often require that employees engage in intellectual risk taking (IRT) by being resourceful, trying new things, and asking questions even at the risk of making a mistake or feeling inadequate. This research seeks to identify variables that increase student IRT. Controlling for individual…

Distance Education Infrastructure for Rural Areas Using Java as a Development Tool.

ERIC Educational Resources Information Center

Ndinga, S. S.; Clayton, P.

New information technology is rapidly becoming part of the localized education process, while offering the tools and the infrastructure for the establishment of a distance education process. At Rhodes University (South Africa), an Interactive Remote Tutorial System (IRTS) was built to support distance education. IRTS will be used as an…

IRT Model Selection Methods for Dichotomous Items

ERIC Educational Resources Information Center

Kang, Taehoon; Cohen, Allan S.

2007-01-01

Fit of the model to the data is important if the benefits of item response theory (IRT) are to be obtained. In this study, the authors compared model selection results using the likelihood ratio test, two information-based criteria, and two Bayesian methods. An example illustrated the potential for inconsistency in model selection depending on…

IRT-ZIP Modeling for Multivariate Zero-Inflated Count Data

ERIC Educational Resources Information Center

Wang, Lijuan

2010-01-01

This study introduces an item response theory-zero-inflated Poisson (IRT-ZIP) model to investigate psychometric properties of multiple items and predict individuals' latent trait scores for multivariate zero-inflated count data. In the model, two link functions are used to capture two processes of the zero-inflated count data. Item parameters are…

Cognitive psychology meets psychometric theory: on the relation between process models for decision making and latent variable models for individual differences.

PubMed

van der Maas, Han L J; Molenaar, Dylan; Maris, Gunter; Kievit, Rogier A; Borsboom, Denny

2011-04-01

This article analyzes latent variable models from a cognitive psychology perspective. We start by discussing work by Tuerlinckx and De Boeck (2005), who proved that a diffusion model for 2-choice response processes entails a 2-parameter logistic item response theory (IRT) model for individual differences in the response data. Following this line of reasoning, we discuss the appropriateness of IRT for measuring abilities and bipolar traits, such as pro versus contra attitudes. Surprisingly, if a diffusion model underlies the response processes, IRT models are appropriate for bipolar traits but not for ability tests. A reconsideration of the concept of ability that is appropriate for such situations leads to a new item response model for accuracy and speed based on the idea that ability has a natural zero point. The model implies fundamentally new ways to think about guessing, response speed, and person fit in IRT. We discuss the relation between this model and existing models as well as implications for psychology and psychometrics. 2011 APA, all rights reserved

New Icing Cloud Simulation System at the NASA Glenn Research Center Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Irvine, Thomas B.; Oldenburg, John R.; Sheldon, David W.

1999-01-01

A new spray bar system was designed, fabricated, and installed in the NASA Glenn Research Center's Icing Research Tunnel (IRT). This system is key to the IRT's ability to do aircraft in-flight icing cloud simulation. The performance goals and requirements levied on the design of the new spray bar system included increased size of the uniform icing cloud in the IRT test section, faster system response time, and increased coverage of icing conditions as defined in Appendix C of the Federal Aviation Regulation (FAR), Part 25 and Part 29. Through significant changes to the mechanical and electrical designs of the previous-generation spray bar system, the performance goals and requirements were realized. Postinstallation aerodynamic and icing cloud calibrations were performed to quantify the changes and improvements made to the IRT test section flow quality and icing cloud characteristics. The new and improved capability to simulate aircraft encounters with in-flight icing clouds ensures that the 1RT will continue to provide a satisfactory icing ground-test simulation method to the aeronautics community.

Results and Conclusions from the NASA Isokinetic Total Water Content Probe 2009 IRT Test

NASA Technical Reports Server (NTRS)

Reehorst, Andrew; Brinker, David

2010-01-01

The NASA Glenn Research Center has developed and tested a Total Water Content Isokinetic Sampling Probe. Since, by its nature, it is not sensitive to cloud water particle phase nor size, it is particularly attractive to support super-cooled large droplet and high ice water content aircraft icing studies. The instrument comprises the Sampling Probe, Sample Flow Control, and Water Vapor Measurement subsystems. Results and conclusions are presented from probe tests in the NASA Glenn Icing Research Tunnel (IRT) during January and February 2009. The use of reference probe heat and the control of air pressure in the water vapor measurement subsystem are discussed. Several run-time error sources were found to produce identifiable signatures that are presented and discussed. Some of the differences between measured Isokinetic Total Water Content Probe and IRT calibration seems to be caused by tunnel humidification and moisture/ice crystal blow around. Droplet size, airspeed, and liquid water content effects also appear to be present in the IRT calibration. Based upon test results, the authors provide recommendations for future Isokinetic Total Water Content Probe development.

The Infrared-Optical Telescope (IRT) of the Exist Observatory

NASA Technical Reports Server (NTRS)

Kutyrev, Alexander; Bloom, Joshua; Gehrels, Neil; Golisano, Craig; Gong, Quan; Grindlay, Jonathan; Moseley, Samuel; Woodgate, Bruce

2010-01-01

The IRT is a 1.1m visible and infrared passively cooled telescope, which can locate, identify and obtain spectra of GRB afterglows at redshifts up to z 20. It will also acquire optical-IR, imaging and spectroscopy of AGN and transients discovered by the EXIST (The Energetic X-ray Imaging Survey Telescope). The IRT imaging and spectroscopic capabilities cover a broad spectral range from 0.32.2m in four bands. The identical fields of view in the four instrument bands are each split in three subfields: imaging, objective prism slitless for the field and objective prism single object slit low resolution spectroscopy, and high resolution long slit on single object. This allows the instrument, to do simultaneous broadband photometry or spectroscopy of the same object over the full spectral range, thus greatly improving the efficiency of the observatory and its detection limits. A prompt follow up (within three minutes) of the transient discovered by the EXIST makes IRT a unique tool for detection and study of these events, which is particularly valuable at wavelengths unavailable to the ground based observatories.

Effect of the stimulus frequency and pulse number of repetitive transcranial magnetic stimulation on the inter-reversal time of perceptual reversal on the right superior parietal lobule

NASA Astrophysics Data System (ADS)

Nojima, Kazuhisa; Ge, Sheng; Katayama, Yoshinori; Ueno, Shoogo; Iramina, Keiji

2010-05-01

The aim of this study is to investigate the effect of the stimulus frequency and pulses number of repetitive transcranial magnetic stimulation (rTMS) on the inter-reversal time (IRT) of perceptual reversal on the right superior parietal lobule (SPL). The spinning wheel illusion was used as the ambiguous figures stimulation in this study. To investigate the rTMS effect over the right SPL during perceptual reversal, 0.25 Hz 60 pulse, 1 Hz 60 pulse, 0.5 Hz 120 pulse, 1 Hz 120 pulse, and 1 Hz 240 pulse biphasic rTMS at 90% of resting motor threshold was applied over the right SPL and the right posterior temporal lobe (PTL), respectively. As a control, a no TMS was also conducted. It was found that rTMS on 0.25 Hz 60 pulse and 1 Hz 60 pulse applied over the right SPL caused shorter IRT. In contrast, it was found that rTMS on 1 Hz 240-pulse applied over the right SPL caused longer IRT. On the other hand, there is no significant difference between IRTs when the rTMS on 0.5 Hz 120 pulse and 1 Hz 120 pulse were applied over the right SPL. Therefore, the applying of rTMS over the right SPL suggests that the IRT of perceptual reversal is effected by the rTMS conditions such as the stimulus frequency and the number of pulses.

Robust Rate Control System Designs for a Submersible

DTIC Science & Technology

1984-05-01

Y~ VP + +p 0 hByG +. 2 .-YII qo(Yp 9 4+ 0* CRFW + q( qva +p0 (Ypq I=G +r0 (Yqr SXG + 3q+ + Ar l [ Y - a) + 0 ar + y n 1 )+v[8~IrT~ Jw-) rn o e{IrI I I...for Information and Decision Systems 2 . 1 ’- ACIOWDGEMENTS I would like to express my sincerest thanks to my thesis ad- visor, Lena Valavani, for her...10 1 INTRODUCTION ............................................ 11 1.1 Background......................................... 11 1.2

Comparison of fracture strength and failure mode of different ceramic implant abutments.

PubMed

Elsayed, Adham; Wille, Sebastian; Al-Akhali, Majed; Kern, Matthias

2017-04-01

The whitish color of zirconia (ZrO 2 ) abutments offers favorable esthetics compared with the grayish color of titanium (Ti) abutments. Nonetheless, ZrO 2 has greater opacity, making it difficult to achieve natural tooth color. Therefore, lithium disilicate (LaT) abutments have been suggested to replace metal abutments. The purpose of this in vitro study was to evaluate the fracture strength and failure mode of single-tooth implant restorations using ZrO 2 and LaT abutments, and to compare them with titanium (Ti) abutments. Five different types of abutments, Ti; ZrO 2 with no metal base; ZrO 2 with a metal base (ZrT); LaT; and LaT combination abutment and crown (LcT) were assembled on 40 Ti implants and restored with LaT crowns. Specimens were subjected to quasistatic loading using a universal testing machine, until the implant-abutment connection failed. As bending of the metal would be considered a clinical failure, the values of force (N) at which the plastic deformation of the metal occurred were calculated, and the rate of deformation was analyzed. Statistical analysis was done using the Mann-Whitney U test (α=.05). Group ZrO 2 revealed the lowest resistance to failure with a mean of 202 ±33 N. Groups ZrT, LaT, and LaC withstood higher forces without fracture or debonding of the ceramic suprastructure, and failure was due to deformation of metal bases, with no statistically significant differences between these groups regarding the bending behavior. Within the limitations of this in vitro study, it was concluded that LaT abutments have the potential to withstand the physiological occlusal forces that occur in the anterior region and that ZrO 2 abutments combined with Ti inserts have much higher fracture strength than pure ZrO 2 abutments. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

The role of ZIP transporters and group F bZIP transcription factors in the Zn-deficiency response of wheat (Triticum aestivum).

PubMed

Evens, Nicholas P; Buchner, Peter; Williams, Lorraine E; Hawkesford, Malcolm J

2017-10-01

Understanding the molecular basis of zinc (Zn) uptake and transport in staple cereal crops is critical for improving both Zn content and tolerance to low-Zn soils. This study demonstrates the importance of group F bZIP transcription factors and ZIP transporters in responses to Zn deficiency in wheat (Triticum aestivum). Seven group F TabZIP genes and 14 ZIPs with homeologs were identified in hexaploid wheat. Promoter analysis revealed the presence of Zn-deficiency-response elements (ZDREs) in a number of the ZIPs. Functional complementation of the zrt1/zrt2 yeast mutant by TaZIP3, -6, -7, -9 and -13 supported an ability to transport Zn. Group F TabZIPs contain the group-defining cysteine-histidine-rich motifs, which are the predicted binding site of Zn 2+ in the Zn-deficiency response. Conservation of these motifs varied between the TabZIPs suggesting that individual TabZIPs may have specific roles in the wheat Zn-homeostatic network. Increased expression in response to low Zn levels was observed for several of the wheat ZIPs and bZIPs; this varied temporally and spatially suggesting specific functions in the response mechanism. The ability of the group F TabZIPs to bind to specific ZDREs in the promoters of TaZIPs indicates a conserved mechanism in monocots and dicots in responding to Zn deficiency. In support of this, TabZIPF1-7DL and TabZIPF4-7AL afforded a strong level of rescue to the Arabidopsis hypersensitive bzip19 bzip23 double mutant under Zn deficiency. These results provide a greater understanding of Zn-homeostatic mechanisms in wheat, demonstrating an expanded repertoire of group F bZIP transcription factors, adding to the complexity of Zn homeostasis. © 2017 The Authors The Plant Journal published by John Wiley & Sons Ltd and Society for Experimental Biology.

Using a Linear Regression Method to Detect Outliers in IRT Common Item Equating

ERIC Educational Resources Information Center

He, Yong; Cui, Zhongmin; Fang, Yu; Chen, Hanwei

2013-01-01

Common test items play an important role in equating alternate test forms under the common item nonequivalent groups design. When the item response theory (IRT) method is applied in equating, inconsistent item parameter estimates among common items can lead to large bias in equated scores. It is prudent to evaluate inconsistency in parameter…

Robust Scale Transformation Methods in IRT True Score Equating under Common-Item Nonequivalent Groups Design

ERIC Educational Resources Information Center

He, Yong

2013-01-01

Common test items play an important role in equating multiple test forms under the common-item nonequivalent groups design. Inconsistent item parameter estimates among common items can lead to large bias in equated scores for IRT true score equating. Current methods extensively focus on detection and elimination of outlying common items, which…

Item Response Data Analysis Using Stata Item Response Theory Package

ERIC Educational Resources Information Center

Yang, Ji Seung; Zheng, Xiaying

2018-01-01

The purpose of this article is to introduce and review the capability and performance of the Stata item response theory (IRT) package that is available from Stata v.14, 2015. Using a simulated data set and a publicly available item response data set extracted from Programme of International Student Assessment, we review the IRT package from…

A Note on the Equivalence between Observed and Expected Information Functions with Polytomous IRT Models

ERIC Educational Resources Information Center

Magis, David

2015-01-01

The purpose of this note is to study the equivalence of observed and expected (Fisher) information functions with polytomous item response theory (IRT) models. It is established that observed and expected information functions are equivalent for the class of divide-by-total models (including partial credit, generalized partial credit, rating…

Effects of Differential Item Functioning on Examinees' Test Performance and Reliability of Test

ERIC Educational Resources Information Center

Lee, Yi-Hsuan; Zhang, Jinming

2017-01-01

Simulations were conducted to examine the effect of differential item functioning (DIF) on measurement consequences such as total scores, item response theory (IRT) ability estimates, and test reliability in terms of the ratio of true-score variance to observed-score variance and the standard error of estimation for the IRT ability parameter. The…

Pretest-Posttest-Posttest Multilevel IRT Modeling of Competence Growth of Students in Higher Education in Germany

ERIC Educational Resources Information Center

Schmidt, Susanne; Zlatkin-Troitschanskaia, Olga; Fox, Jean-Paul

2016-01-01

Longitudinal research in higher education faces several challenges. Appropriate methods of analyzing competence growth of students are needed to deal with those challenges and thereby obtain valid results. In this article, a pretest-posttest-posttest multivariate multilevel IRT model for repeated measures is introduced which is designed to address…

Linking Parameters Estimated with the Generalized Graded Unfolding Model: A Comparison of the Accuracy of Characteristic Curve Methods

ERIC Educational Resources Information Center

Anderson Koenig, Judith; Roberts, James S.

2007-01-01

Methods for linking item response theory (IRT) parameters are developed for attitude questionnaire responses calibrated with the generalized graded unfolding model (GGUM). One class of IRT linking methods derives the linking coefficients by comparing characteristic curves, and three of these methods---test characteristic curve (TCC), item…

Detecting DIF in Polytomous Items Using MACS, IRT and Ordinal Logistic Regression

ERIC Educational Resources Information Center

Elosua, Paula; Wells, Craig

2013-01-01

The purpose of the present study was to compare the Type I error rate and power of two model-based procedures, the mean and covariance structure model (MACS) and the item response theory (IRT), and an observed-score based procedure, ordinal logistic regression, for detecting differential item functioning (DIF) in polytomous items. A simulation…

Standard Error Estimation of 3PL IRT True Score Equating with an MCMC Method

ERIC Educational Resources Information Center

Liu, Yuming; Schulz, E. Matthew; Yu, Lei

2008-01-01

A Markov chain Monte Carlo (MCMC) method and a bootstrap method were compared in the estimation of standard errors of item response theory (IRT) true score equating. Three test form relationships were examined: parallel, tau-equivalent, and congeneric. Data were simulated based on Reading Comprehension and Vocabulary tests of the Iowa Tests of…

Identifying Aberrant Responding: Use of Multiple Measures

ERIC Educational Resources Information Center

Steinkamp, Susan Christa

2017-01-01

For test scores that rely on the accurate estimation of ability via an IRT model, their use and interpretation is dependent upon the assumption that the IRT model fits the data. Examinees who do not put forth full effort in answering test questions, have prior knowledge of test content, or do not approach a test with the intent of answering…

Evaluation of the IRT Parameter Invariance Property for the MCAT.

ERIC Educational Resources Information Center

Kelkar, Vinaya; Wightman, Linda F.; Luecht, Richard M.

The purpose of this study was to investigate the viability of the property of parameter invariance for the one-parameter (1P), two-parameter (2P), and three-parameter (3P) item response theory (IRT) models for the Medical College Admissions Tests (MCAT). Invariance of item parameters across different gender, ethnic, and language groups and the…

Ramsay-Curve Item Response Theory for the Three-Parameter Logistic Item Response Model

ERIC Educational Resources Information Center

Woods, Carol M.

2008-01-01

In Ramsay-curve item response theory (RC-IRT), the latent variable distribution is estimated simultaneously with the item parameters of a unidimensional item response model using marginal maximum likelihood estimation. This study evaluates RC-IRT for the three-parameter logistic (3PL) model with comparisons to the normal model and to the empirical…

IRT-LR-DIF with Estimation of the Focal-Group Density as an Empirical Histogram

ERIC Educational Resources Information Center

Woods, Carol M.

2008-01-01

Item response theory-likelihood ratio-differential item functioning (IRT-LR-DIF) is used to evaluate the degree to which items on a test or questionnaire have different measurement properties for one group of people versus another, irrespective of group-mean differences on the construct. Usually, the latent distribution is presumed normal for both…

Comparing the IRT Pre-equating and Section Pre-equating: A Simulation Study.

ERIC Educational Resources Information Center

Hwang, Chi-en; Cleary, T. Anne

The results obtained from two basic types of pre-equatings of tests were compared: the item response theory (IRT) pre-equating and section pre-equating (SPE). The simulated data were generated from a modified three-parameter logistic model with a constant guessing parameter. Responses of two replication samples of 3000 examinees on two 72-item…

Case Study – Idling Reduction Technologies for Emergency Service Vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laughlin, Michael; Owens, Russell J.

2016-01-01

This case study explores the use of idle reduction technologies (IRTs) on emergency service vehicles in police, fire, and ambulance applications. Various commercially available IRT systems and approaches can decrease, or ultimately eliminate, engine idling. Fleets will thus save money on fuel, and will also decrease their criteria pollutant emissions, greenhouse gas emissions, and noise.

Measuring Constructs in Family Science: How Can Item Response Theory Improve Precision and Validity?

ERIC Educational Resources Information Center

Gordon, Rachel A.

2015-01-01

This article provides family scientists with an understanding of contemporary measurement perspectives and the ways in which item response theory (IRT) can be used to develop measures with desired evidence of precision and validity for research uses. The article offers a nontechnical introduction to some key features of IRT, including its…

Hybrid Model of IRT and Latent Class Models.

ERIC Educational Resources Information Center

Yamamoto, Kentaro

This study developed a hybrid of item response theory (IRT) models and latent class models, which combined the strengths of each type of model. The primary motivation for developing the new model is to describe characteristics of examinees' knowledge at the time of the examination. Hence, the application of the model lies mainly in so-called…

Translation Fidelity of Psychological Scales: An Item Response Theory Analysis of an Individualism-Collectivism Scale.

ERIC Educational Resources Information Center

Bontempo, Robert

1993-01-01

Describes a method for assessing the quality of translations based on item response theory (IRT). Results from the IRT technique with French and Chinese versions of a scale measuring individualism-collectivism for samples of 250 U.S., 357 French, and 290 Chinese undergraduates show how several biased items are detected. (SLD)

A Systematic Comparison between Classical Optimal Scaling and the Two-Parameter IRT Model

ERIC Educational Resources Information Center

Warrens, Matthijs J.; de Gruijter, Dato N. M.; Heiser, Willem J.

2007-01-01

In this article, the relationship between two alternative methods for the analysis of multivariate categorical data is systematically explored. It is shown that the person score of the first dimension of classical optimal scaling correlates strongly with the latent variable for the two-parameter item response theory (IRT) model. Next, under the…

ResidPlots-2: Computer Software for IRT Graphical Residual Analyses

ERIC Educational Resources Information Center

Liang, Tie; Han, Kyung T.; Hambleton, Ronald K.

2009-01-01

This article discusses the ResidPlots-2, a computer software that provides a powerful tool for IRT graphical residual analyses. ResidPlots-2 consists of two components: a component for computing residual statistics and another component for communicating with users and for plotting the residual graphs. The features of the ResidPlots-2 software are…

A Comparison of IRT Proficiency Estimation Methods under Adaptive Multistage Testing

ERIC Educational Resources Information Center

Kim, Sooyeon; Moses, Tim; Yoo, Hanwook

2015-01-01

This inquiry is an investigation of item response theory (IRT) proficiency estimators' accuracy under multistage testing (MST). We chose a two-stage MST design that includes four modules (one at Stage 1, three at Stage 2) and three difficulty paths (low, middle, high). We assembled various two-stage MST panels (i.e., forms) by manipulating two…

Examining the Effectiveness of Test Accommodation Using DIF and a Mixture IRT Model

ERIC Educational Resources Information Center

Cho, Hyun-Jeong; Lee, Jaehoon; Kingston, Neal

2012-01-01

This study examined the validity of test accommodation in third-eighth graders using differential item functioning (DIF) and mixture IRT models. Two data sets were used for these analyses. With the first data set (N = 51,591) we examined whether item type (i.e., story, explanation, straightforward) or item features were associated with item…

How Often Is the Misfit of Item Response Theory Models Practically Significant?

ERIC Educational Resources Information Center

Sinharay, Sandip; Haberman, Shelby J.

2014-01-01

Standard 3.9 of the Standards for Educational and Psychological Testing ([, 1999]) demands evidence of model fit when item response theory (IRT) models are employed to data from tests. Hambleton and Han ([Hambleton, R. K., 2005]) and Sinharay ([Sinharay, S., 2005]) recommended the assessment of practical significance of misfit of IRT models, but…

A Comparison between Linear IRT Observed-Score Equating and Levine Observed-Score Equating under the Generalized Kernel Equating Framework

ERIC Educational Resources Information Center

Chen, Haiwen

2012-01-01

In this article, linear item response theory (IRT) observed-score equating is compared under a generalized kernel equating framework with Levine observed-score equating for nonequivalent groups with anchor test design. Interestingly, these two equating methods are closely related despite being based on different methodologies. Specifically, when…

An Estimation Procedure for the Structural Parameters of the Unified Cognitive/IRT Model.

ERIC Educational Resources Information Center

Jiang, Hai; And Others

L. V. DiBello, W. F. Stout, and L. A. Roussos (1993) have developed a new item response model, the Unified Model, which brings together the discrete, deterministic aspects of cognition favored by cognitive scientists, and the continuous, stochastic aspects of test response behavior that underlie item response theory (IRT). The Unified Model blends…

An Extension of Least Squares Estimation of IRT Linking Coefficients for the Graded Response Model

ERIC Educational Resources Information Center

Kim, Seonghoon

2010-01-01

The three types (generalized, unweighted, and weighted) of least squares methods, proposed by Ogasawara, for estimating item response theory (IRT) linking coefficients under dichotomous models are extended to the graded response model. A simulation study was conducted to confirm the accuracy of the extended formulas, and a real data study was…

The Effect of Including or Excluding Students with Testing Accommodations on IRT Calibrations.

ERIC Educational Resources Information Center

Karkee, Thakur; Lewis, Dan M.; Barton, Karen; Haug, Carolyn

This study aimed to determine the degree to which the inclusion of accommodated students with disabilities in the calibration sample affects the characteristics of item parameters and the test results. Investigated were effects on test reliability, item fit to the applicable item response theory (IRT) model, item parameter estimates, and students'…

A Comparison of General Diagnostic Models (GDM) and Bayesian Networks Using a Middle School Mathematics Test

ERIC Educational Resources Information Center

Wu, Haiyan

2013-01-01

General diagnostic models (GDMs) and Bayesian networks are mathematical frameworks that cover a wide variety of psychometric models. Both extend latent class models, and while GDMs also extend item response theory (IRT) models, Bayesian networks can be parameterized using discretized IRT. The purpose of this study is to examine similarities and…

Assessing the Item Response Theory with Covariate (IRT-C) Procedure for Ascertaining Differential Item Functioning

ERIC Educational Resources Information Center

Tay, Louis; Vermunt, Jeroen K.; Wang, Chun

2013-01-01

We evaluate the item response theory with covariates (IRT-C) procedure for assessing differential item functioning (DIF) without preknowledge of anchor items (Tay, Newman, & Vermunt, 2011). This procedure begins with a fully constrained baseline model, and candidate items are tested for uniform and/or nonuniform DIF using the Wald statistic.…

Comparison of IRT and CTT Using Secondary School Reading Comprehension Assessments

ERIC Educational Resources Information Center

Coggins, Joanne V.; Kim, Jwa K.; Briggs, Laura C.

2017-01-01

The Gates-MacGinitie Reading Comprehension Test, fourth edition (GMRT-4) and the ACT Reading Tests (ACT-R) were administered to 423 high school students in order to explore the similarities and dissimilarities of data produced through classical test theory (CTT) and item response theory (IRT) analysis. Despite the many advantages of IRT…

Mixture IRT Model with a Higher-Order Structure for Latent Traits

ERIC Educational Resources Information Center

Huang, Hung-Yu

2017-01-01

Mixture item response theory (IRT) models have been suggested as an efficient method of detecting the different response patterns derived from latent classes when developing a test. In testing situations, multiple latent traits measured by a battery of tests can exhibit a higher-order structure, and mixtures of latent classes may occur on…

Using SAS PROC MCMC for Item Response Theory Models

PubMed Central

Samonte, Kelli

2014-01-01

Interest in using Bayesian methods for estimating item response theory models has grown at a remarkable rate in recent years. This attentiveness to Bayesian estimation has also inspired a growth in available software such as WinBUGS, R packages, BMIRT, MPLUS, and SAS PROC MCMC. This article intends to provide an accessible overview of Bayesian methods in the context of item response theory to serve as a useful guide for practitioners in estimating and interpreting item response theory (IRT) models. Included is a description of the estimation procedure used by SAS PROC MCMC. Syntax is provided for estimation of both dichotomous and polytomous IRT models, as well as a discussion on how to extend the syntax to accommodate more complex IRT models. PMID:29795834

Structure and Measurement of Depression in Youth: Applying Item Response Theory to Clinical Data

PubMed Central

Cole, David A.; Cai, Li; Martin, Nina C.; Findling, Robert L; Youngstrom, Eric A.; Garber, Judy; Curry, John F.; Hyde, Janet S.; Essex, Marilyn J.; Compas, Bruce E.; Goodyer, Ian M.; Rohde, Paul; Stark, Kevin D.; Slattery, Marcia J.; Forehand, Rex

2013-01-01

Goals of the paper were to use item response theory (IRT) to assess the relation of depressive symptoms to the underlying dimension of depression and to demonstrate how IRT-based measurement strategies can yield more reliable data about depression severity than conventional symptom counts. Participants were 3403 clinic and nonclinic children and adolescents from 12 contributing samples, all of whom received the Kiddie Schedule of Affective Disorders and Schizophrenia for school-aged children. Results revealed that some symptoms reflected higher levels of depression and were more discriminating than others. Results further demonstrated that utilization of IRT-based information about symptom severity and discriminability in the measurement of depression severity can reduce measurement error and increase measurement fidelity. PMID:21534696

Alzheimer's Disease Assessment: A Review and Illustrations Focusing on Item Response Theory Techniques.

PubMed

Balsis, Steve; Choudhury, Tabina K; Geraci, Lisa; Benge, Jared F; Patrick, Christopher J

2018-04-01

Alzheimer's disease (AD) affects neurological, cognitive, and behavioral processes. Thus, to accurately assess this disease, researchers and clinicians need to combine and incorporate data across these domains. This presents not only distinct methodological and statistical challenges but also unique opportunities for the development and advancement of psychometric techniques. In this article, we describe relatively recent research using item response theory (IRT) that has been used to make progress in assessing the disease across its various symptomatic and pathological manifestations. We focus on applications of IRT to improve scoring, test development (including cross-validation and adaptation), and linking and calibration. We conclude by describing potential future multidimensional applications of IRT techniques that may improve the precision with which AD is measured.

AhIRT1 and AhNRAMP1 metal transporter expression correlates with Cd uptake in peanuts under iron deficiency

PubMed Central

Xia, Shenglan; Deng, Rubo; Liu, Caifeng; Shi, Gangrong

2017-01-01

Fe deficiency may increase Cd accumulation in peanuts. However, the mechanisms are not yet fully understood. In the present study, two contrasting peanut cultivars, Luhua 8 (low seed-Cd cultivar) and Zhenghong 3 (high seed-Cd cultivar) were used to investigate the effect of Fe deficiency on the uptake and accumulation of cadmium (Cd) by hydroponic experiments. Under Fe-sufficient conditions, compared with Luhua 8, Zhenghong 3 had higher specific root length (SRL) and proportion of fine roots with a lower Km for Cd and showed slightly higher expression of AhIRT1 and AhNRAMP1 in the roots. These traits may be responsible for high capacity for Cd accumulation in Zhenghong 3. Under Fe deficiency, the increase of Cd accumulation was much larger in Zhenghong 3 than in Luhua 8. Kinetics studies revealed that the Vmax for Cd influx was 1.56-fold higher in Fe-deficient plants than in Fe-sufficient plants for Zhenghong 3, versus 0.48-fold higher for Luhua 8. Moreover, the increased expression levels of AhIRT1 and AhNRAMP1 induced by Fe deficiency was higher in Zhenghong 3 than in Luhua 8. Yeast complementation assays suggested that the AhIRT1 and AhNRAMP1 may function as transporters involved in Cd uptake. In conclusion, the different Cd accumulation between the two cultivars under Fe deficiency may be correlated with Vmax value for Cd uptake and the expression levels of AhIRT1 and AhNRAMP1 in the roots. PMID:28981520

Psychometric characteristics of daily diaries for the Patient-Reported Outcomes Measurement Information System (PROMIS®): a preliminary investigation.

PubMed

Schneider, Stefan; Choi, Seung W; Junghaenel, Doerte U; Schwartz, Joseph E; Stone, Arthur A

2013-09-01

The Patient-Reported Outcomes (PRO) Measurement Information System (PROMIS(®)) has developed assessment tools for numerous PROs, most using a 7-day recall format. We examined whether modifying the recall period for use in daily diary research would affect the psychometric characteristics of several PROMIS measures. Daily versions of short-forms for three PROMIS domains (pain interference, fatigue, depression) were administered to a general population sample (n = 100) for 28 days. Analyses used multilevel item response theory (IRT) models. We examined differential item functioning (DIF) across recall periods by comparing the IRT parameters from the daily data with the PROMIS 7-day recall IRT parameters. Additionally, we examined whether the IRT parameters for day-to-day within-person changes are invariant to those for between-person (cross-sectional) differences in PROs. Dimensionality analyses of the daily data suggested a single dimension for each PRO domain, consistent with PROMIS instruments. One-third of the daily items showed uniform DIF when compared with PROMIS 7-day recall, but the impact of DIF on the scale level was minor. IRT parameters for within-person changes differed from between-person parameters for 3 depression items, which were more sensitive for measuring change than between-person differences, but not for pain interference and fatigue items. Notably, mean scores from daily diaries were significantly lower than the PROMIS 7-day recall norms. The results provide initial evidence supporting the adaptation of PROMIS measures for daily diary research. However, scores from daily diaries cannot be directly interpreted on PROMIS norms established for 7-day recall.

The Effect of Fasting Duration on Baseline Blood Glucose Concentration, Blood Insulin Concentration, Glucose/Insulin Ratio, Oral Sugar Test, and Insulin Response Test Results in Horses.

PubMed

Bertin, F R; Taylor, S D; Bianco, A W; Sojka-Kritchevsky, J E

2016-09-01

Published descriptions of the oral sugar test (OST) and insulin response test (IRT) have been inconsistent when specifying the protocol for fasting horses before testing. The purpose of our study was to examine the effect of fasting duration on blood glucose concentration, blood insulin concentration, glucose/insulin ratio, OST, and IRT results in horses. Ten healthy adult horses. Both OST and IRT were performed on horses without fasting and after fasting for 3, 6, and 12 hours. Thus, 8 tests were performed per horse in a randomized order. Blood collected at the initial time point of the OST was analysed for both blood glucose and serum insulin concentrations so that baseline concentrations and the glucose/insulin ratio could be determined. Unless fasted, horses had free-choice access to grass hay. There was no effect of fasting and fasting duration on blood glucose concentration, serum insulin concentration, glucose/insulin ratio, or the OST. Response to insulin in the IRT was decreased in fasted horses. The effect increased with fasting duration, with the least response to insulin administration after a 12-hour fast. These data indicate that insulin sensitivity is not a fixed trait in horses. Fasting a horse is not recommended for a glucose/insulin ratio or IRT, and fasting a horse for 3 hours is recommended for the OST. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

Immediate list recall as a measure of short-term episodic memory: insights from the serial position effect and item response theory.

PubMed

Gavett, Brandon E; Horwitz, Julie E

2012-03-01

The serial position effect shows that two interrelated cognitive processes underlie immediate recall of a supraspan word list. The current study used item response theory (IRT) methods to determine whether the serial position effect poses a threat to the construct validity of immediate list recall as a measure of verbal episodic memory. Archival data were obtained from a national sample of 4,212 volunteers aged 28-84 in the Midlife Development in the United States study. Telephone assessment yielded item-level data for a single immediate recall trial of the Rey Auditory Verbal Learning Test (RAVLT). Two parameter logistic IRT procedures were used to estimate item parameters and the Q(1) statistic was used to evaluate item fit. A two-dimensional model better fit the data than a unidimensional model, supporting the notion that list recall is influenced by two underlying cognitive processes. IRT analyses revealed that 4 of the 15 RAVLT items (1, 12, 14, and 15) were misfit (p < .05). Item characteristic curves for items 14 and 15 decreased monotonically, implying an inverse relationship between the ability level and the probability of recall. Elimination of the four misfit items provided better fit to the data and met necessary IRT assumptions. Performance on a supraspan list learning test is influenced by multiple cognitive abilities; failure to account for the serial position of words decreases the construct validity of the test as a measure of episodic memory and may provide misleading results. IRT methods can ameliorate these problems and improve construct validity.

Development and evaluation of the PI-G: a three-scale measure based on the German translation of the PROMIS ® pain interference item bank.

PubMed

Farin, Erik; Nagl, Michaela; Gramm, Lukas; Heyduck, Katja; Glattacker, Manuela

2014-05-01

Study aim was to translate the PROMIS(®) pain interference (PI) item bank (41 items) into German, test its psychometric properties in patients with chronic low back pain and develop static subforms. We surveyed N = 262 patients undergoing rehabilitation who were asked to fill out questionnaires at the beginning and 2 weeks after the end of rehabilitation, applying the Oswestry Disability Index (ODI) and Pain Disability Index (PDI) in addition to the PROMIS(®) PI items. For psychometric testing, a 1-parameter item response theory (IRT) model was used. Exploratory and confirmatory factor analyses as well as reliability and construct validity analyses were conducted. The assumptions regarding IRT scaling of the translated PROMIS(®) PI item bank as a whole were not confirmed. However, we succeeded in devising three static subforms (PI-G scales: PI mental 13 items, PI functional 11 items, PI physical 4 items), revealing good psychometric properties. The PI-G scales in their static form can be recommended for use in German-speaking countries. Their strengths versus the ODI and PDI are that pain interference is assessed in a differentiated manner and that several psychometric values are somewhat better than those associated with the ODI and PDI (distribution properties, IRT model fit, reliability). To develop an IRT-scaled item bank of the German translations of the PROMIS(®) PI items, it would be useful to have additional studies (e.g., with larger sample sizes and using a 2-parameter IRT model).

Estimating Non-Normal Latent Trait Distributions within Item Response Theory Using True and Estimated Item Parameters

ERIC Educational Resources Information Center

Sass, D. A.; Schmitt, T. A.; Walker, C. M.

2008-01-01

Item response theory (IRT) procedures have been used extensively to study normal latent trait distributions and have been shown to perform well; however, less is known concerning the performance of IRT with non-normal latent trait distributions. This study investigated the degree of latent trait estimation error under normal and non-normal…

Civil Military Programs. Stronger Oversight of the Innovative Readiness Training Program Needed for Better Compliance. Report to Congressional Committees.

ERIC Educational Resources Information Center

General Accounting Office, Washington, DC. National Security and International Affairs Div.

A study reviewed the U.S. Department of Defense's (DOD) training projects that support nondefense activity under its Innovative Readiness Training (IRT) Program. The report examines the following: extent, nature, and cost of civil military projects; consistency of DOD's guidance on the IRT Program with statutory requirements; conformity of…

Demonstrating the Difference between Classical Test Theory and Item Response Theory Using Derived Test Data

ERIC Educational Resources Information Center

Magno, Carlo

2009-01-01

The present report demonstrates the difference between classical test theory (CTT) and item response theory (IRT) approach using an actual test data for chemistry junior high school students. The CTT and IRT were compared across two samples and two forms of test on their item difficulty, internal consistency, and measurement errors. The specific…

Anchor Selection Strategies for DIF Analysis: Review, Assessment, and New Approaches

ERIC Educational Resources Information Center

Kopf, Julia; Zeileis, Achim; Strobl, Carolin

2015-01-01

Differential item functioning (DIF) indicates the violation of the invariance assumption, for instance, in models based on item response theory (IRT). For item-wise DIF analysis using IRT, a common metric for the item parameters of the groups that are to be compared (e.g., for the reference and the focal group) is necessary. In the Rasch model,…

Weighting Test Samples in IRT Linking and Equating: Toward an Improved Sampling Design for Complex Equating. Research Report. ETS RR-13-39

ERIC Educational Resources Information Center

Qian, Jiahe; Jiang, Yanming; von Davier, Alina A.

2013-01-01

Several factors could cause variability in item response theory (IRT) linking and equating procedures, such as the variability across examinee samples and/or test items, seasonality, regional differences, native language diversity, gender, and other demographic variables. Hence, the following question arises: Is it possible to select optimal…

Adjusting for Year to Year Rater Variation in IRT Linking--An Empirical Evaluation

ERIC Educational Resources Information Center

Yen, Shu Jing; Ochieng, Charles; Michaels, Hillary; Friedman, Greg

2005-01-01

The main purpose of this study was to illustrate a polytomous IRT-based linking procedure that adjusts for rater variations. Test scores from two administrations of a statewide reading assessment were used. An anchor set of Year 1 students' constructed responses were rescored by Year 2 raters. To adjust for year-to-year rater variation in IRT…

The Measurement of Visuo-Spatial and Verbal-Numerical Working Memory: Development of IRT-Based Scales

ERIC Educational Resources Information Center

Vock, Miriam; Holling, Heinz

2008-01-01

The objective of this study is to explore the potential for developing IRT-based working memory scales for assessing specific working memory components in children (8-13 years). These working memory scales should measure cognitive abilities reliably in the upper range of ability distribution as well as in the normal range, and provide a…

A Comment on Early Student Blunders on Computer-Based Adaptive Tests

ERIC Educational Resources Information Center

Green, Bert F.

2011-01-01

This article refutes a recent claim that computer-based tests produce biased scores for very proficient test takers who make mistakes on one or two initial items and that the "bias" can be reduced by using a four-parameter IRT model. Because the same effect occurs with pattern scores on nonadaptive tests, the effect results from IRT scoring, not…

An NCME Instructional Module on Item-Fit Statistics for Item Response Theory Models

ERIC Educational Resources Information Center

Ames, Allison J.; Penfield, Randall D.

2015-01-01

Drawing valid inferences from item response theory (IRT) models is contingent upon a good fit of the data to the model. Violations of model-data fit have numerous consequences, limiting the usefulness and applicability of the model. This instructional module provides an overview of methods used for evaluating the fit of IRT models. Upon completing…

Item Response Theory with Covariates (IRT-C): Assessing Item Recovery and Differential Item Functioning for the Three-Parameter Logistic Model

ERIC Educational Resources Information Center

Tay, Louis; Huang, Qiming; Vermunt, Jeroen K.

2016-01-01

In large-scale testing, the use of multigroup approaches is limited for assessing differential item functioning (DIF) across multiple variables as DIF is examined for each variable separately. In contrast, the item response theory with covariate (IRT-C) procedure can be used to examine DIF across multiple variables (covariates) simultaneously. To…

Development and Initial Validation of the Medical Fear Survey-Short Version

ERIC Educational Resources Information Center

Olatunji, Bunmi O.; Ebesutani, Chad; Sawchuk, Craig N.; McKay, Dean; Lohr, Jeffrey M.; Kleinknecht, Ronald A.

2012-01-01

The present investigation employs item response theory (IRT) to develop an abbreviated Medical Fear Survey (MFS). Application of IRT analyses in Study 1 (n = 931) to the original 50-item MFS resulted in a 25-item shortened version. Examination of the location parameters also resulted in a reduction of the Likert-type scaling of the MFS by removing…

Generalized IRT Models for Extreme Response Style

ERIC Educational Resources Information Center

Jin, Kuan-Yu; Wang, Wen-Chung

2014-01-01

Extreme response style (ERS) is a systematic tendency for a person to endorse extreme options (e.g., strongly disagree, strongly agree) on Likert-type or rating-scale items. In this study, we develop a new class of item response theory (IRT) models to account for ERS so that the target latent trait is free from the response style and the tendency…

Fitting a Mixture Item Response Theory Model to Personality Questionnaire Data: Characterizing Latent Classes and Investigating Possibilities for Improving Prediction

ERIC Educational Resources Information Center

Maij-de Meij, Annette M.; Kelderman, Henk; van der Flier, Henk

2008-01-01

Mixture item response theory (IRT) models aid the interpretation of response behavior on personality tests and may provide possibilities for improving prediction. Heterogeneity in the population is modeled by identifying homogeneous subgroups that conform to different measurement models. In this study, mixture IRT models were applied to the…

A Primer on the 2- and 3-Parameter Item Response Theory Models.

ERIC Educational Resources Information Center

Thornton, Artist

Item response theory (IRT) is a useful and effective tool for item response measurement if used in the proper context. This paper discusses the sets of assumptions under which responses can be modeled while exploring the framework of the IRT models relative to response testing. The one parameter model, or one parameter logistic model, is perhaps…

Person Response Functions and the Definition of Units in the Social Sciences

ERIC Educational Resources Information Center

Engelhard, George, Jr.; Perkins, Aminah F.

2011-01-01

Humphry (this issue) has written a thought-provoking piece on the interpretation of item discrimination parameters as scale units in item response theory. One of the key features of his work is the description of an item response theory (IRT) model that he calls the logistic measurement function that combines aspects of two traditions in IRT that…

Applying Item Response Theory to the Development of a Screening Adaptation of the Goldman-Fristoe Test of Articulation-Second Edition

ERIC Educational Resources Information Center

Brackenbury, Tim; Zickar, Michael J.; Munson, Benjamin; Storkel, Holly L.

2017-01-01

Purpose: Item response theory (IRT) is a psychometric approach to measurement that uses latent trait abilities (e.g., speech sound production skills) to model performance on individual items that vary by difficulty and discrimination. An IRT analysis was applied to preschoolers' productions of the words on the Goldman-Fristoe Test of…

Rasch Model Parameter Estimation in the Presence of a Nonnormal Latent Trait Using a Nonparametric Bayesian Approach

ERIC Educational Resources Information Center

Finch, Holmes; Edwards, Julianne M.

2016-01-01

Standard approaches for estimating item response theory (IRT) model parameters generally work under the assumption that the latent trait being measured by a set of items follows the normal distribution. Estimation of IRT parameters in the presence of nonnormal latent traits has been shown to generate biased person and item parameter estimates. A…

Accuracy and Variability of Item Parameter Estimates from Marginal Maximum a Posteriori Estimation and Bayesian Inference via Gibbs Samplers

ERIC Educational Resources Information Center

Wu, Yi-Fang

2015-01-01

Item response theory (IRT) uses a family of statistical models for estimating stable characteristics of items and examinees and defining how these characteristics interact in describing item and test performance. With a focus on the three-parameter logistic IRT (Birnbaum, 1968; Lord, 1980) model, the current study examines the accuracy and…

Measuring Anxiety in Visually-Impaired People: A Comparison between the Linear and the Nonlinear IRT Approaches

ERIC Educational Resources Information Center

Ferrando, Pere J.; Pallero, Rafael; Anguiano-Carrasco, Cristina

2013-01-01

The present study has two main interests. First, some pending issues about the psychometric properties of the CTAC (an anxiety questionnaire for blind and visually-impaired people) are assessed using item response theory (IRT). Second, the linear model is compared to the graded response model (GRM) in terms of measurement precision, sensitivity…

Increasing the Number of Replications in Item Response Theory Simulations: Automation through SAS and Disk Operating System

ERIC Educational Resources Information Center

Gagne, Phill; Furlow, Carolyn; Ross, Terris

2009-01-01

In item response theory (IRT) simulation research, it is often necessary to use one software package for data generation and a second software package to conduct the IRT analysis. Because this can substantially slow down the simulation process, it is sometimes offered as a justification for using very few replications. This article provides…

A Comparison of Item Fit Statistics for Mixed IRT Models

ERIC Educational Resources Information Center

Chon, Kyong Hee; Lee, Won-Chan; Dunbar, Stephen B.

2010-01-01

In this study we examined procedures for assessing model-data fit of item response theory (IRT) models for mixed format data. The model fit indices used in this study include PARSCALE's G[superscript 2], Orlando and Thissen's S-X[superscript 2] and S-G[superscript 2], and Stone's chi[superscript 2*] and G[superscript 2*]. To investigate the…

Estimation of a Ramsay-Curve Item Response Theory Model by the Metropolis-Hastings Robbins-Monro Algorithm. CRESST Report 834

ERIC Educational Resources Information Center

Monroe, Scott; Cai, Li

2013-01-01

In Ramsay curve item response theory (RC-IRT, Woods & Thissen, 2006) modeling, the shape of the latent trait distribution is estimated simultaneously with the item parameters. In its original implementation, RC-IRT is estimated via Bock and Aitkin's (1981) EM algorithm, which yields maximum marginal likelihood estimates. This method, however,…

Estimation of a Ramsay-Curve Item Response Theory Model by the Metropolis-Hastings Robbins-Monro Algorithm

ERIC Educational Resources Information Center

Monroe, Scott; Cai, Li

2014-01-01

In Ramsay curve item response theory (RC-IRT) modeling, the shape of the latent trait distribution is estimated simultaneously with the item parameters. In its original implementation, RC-IRT is estimated via Bock and Aitkin's EM algorithm, which yields maximum marginal likelihood estimates. This method, however, does not produce the…

Small helium-cooled infrared telescope experiment for Spacelab-2 (IRT)

NASA Technical Reports Server (NTRS)

Fazio, Giovanni G.

1990-01-01

The Infrared Telescope (IRT) experiment, flown on Spacelab-2, was used to make infrared measurements between 2 and 120 microns. The objectives were multidisciplinary in nature with astrophysical goals of mapping the diffuse cosmic emission and extended infrared sources and technical goals of measuring the induced Shuttle environment, studying properties of superfluid helium in space, and testing various infrared telescope system designs. Astrophysically, new data were obtained on the structure of the Galaxy at near-infrared wavelengths. A summary of the large scale diffuse near-infrared observations of the Galaxy by the IRT is presented, as well as a summary of the preliminary results obtained from this data on the structure of the galactic disk and bulge. The importance of combining CO and near-infrared maps of similar resolution to determine a 3-D model of galactic extinction is demonstrated. The IRT data are used, in conjunction with a proposed galactic model, to make preliminary measurements of the global scale parameters of the Galaxy. During the mission substantial amounts of data were obtained concerning the induced Shuttle environment. An experiment was also performed to measure spacecraft glow in the IR.

Mixture Rasch model for guessing group identification

NASA Astrophysics Data System (ADS)

Siow, Hoo Leong; Mahdi, Rasidah; Siew, Eng Ling

2013-04-01

Several alternative dichotomous Item Response Theory (IRT) models have been introduced to account for guessing effect in multiple-choice assessment. The guessing effect in these models has been considered to be itemrelated. In the most classic case, pseudo-guessing in the three-parameter logistic IRT model is modeled to be the same for all the subjects but may vary across items. This is not realistic because subjects can guess worse or better than the pseudo-guessing. Derivation from the three-parameter logistic IRT model improves the situation by incorporating ability in guessing. However, it does not model non-monotone function. This paper proposes to study guessing from a subject-related aspect which is guessing test-taking behavior. Mixture Rasch model is employed to detect latent groups. A hybrid of mixture Rasch and 3-parameter logistic IRT model is proposed to model the behavior based guessing from the subjects' ways of responding the items. The subjects are assumed to simply choose a response at random. An information criterion is proposed to identify the behavior based guessing group. Results show that the proposed model selection criterion provides a promising method to identify the guessing group modeled by the hybrid model.

Ultralow Dose MSCT Imaging in Dental Implantology

PubMed Central

Widmann, Gerlig; Al-Ekrish, Asma'a A.

2018-01-01

Introduction: The Council Directive 2013/59 Euratom has a clear commitment for keeping medical radiation exposure as low as reasonably achievable and demands a regular review and use of diagnostic reference levels. Methods: In dental implantology, the range of effective doses for cone beam computed tomography (CBCT) shows a broad overlap with multislice computed tomography (MSCT). More recently, ultralow dose imaging with new generations of MSCT scanners may impart radiation doses equal to or lower than CBCT. Dose reductions in MSCT have been further facilitated by the introduction of iterative image reconstruction technology (IRT), which provides substantial noise reduction over the current standard of filtered backward projection (FBP). Aim: The aim of this article is to review the available literature on ultralow dose CT imaging and IRTs in dental implantology imaging and to summarize their influence on spatial and contrast resolution, image noise, tissue density measurements, and validity of linear measurements of the jaws. Conclusion: Application of ultralow dose MSCT with IRT technology in dental implantology offers the potential for very large dose reductions compared with standard dose imaging. Yet, evaluation of various diagnostic tasks related to dental implantology is still needed to confirm the results obtained with various IRTs and ultra-low doses so far. PMID:29492174

Effects of Chinese Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats.

PubMed

Li, Jing-Bin; Xu, Li-Jun; Dong, Hui; Huang, Zhao-Yi; Zhao, Yan; Chen, Guang; Lu, Fu-Er

2013-12-01

The effect of Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats was investigated. The rat model of type 2 diabetes was established by feeding on a high-fat diet for 8 weeks and by subsequently intravenous injection of small doses of streptozotocin. Rats in treatment groups, including the Fructus Mume formula treatment group (FM), the cold property herbs of Fructus Mume formula treatment group (CFM), the warm property herbs of Fructus Mume formula treatment group (WFM), were administrated with Fructus Mume formula and its separated prescription extract by gavage, while the rats in diabetic model group (DM) and metformin group (MET) were given by gavage with normal saline and metformin correspondingly. The body weight before and after treatment was measured, and the oral glucose tolerance test (OGTT) and the insulin release test (IRT) were performed. The homeostasis model assessment-insulin resistance index (HOMA-IR) was calculated. The protein and mRNA expression levels of Insr, β-arrestin-2, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were detected by using Western blotting and RT-PCR respectively. The results demonstrated that, as compared with DM group, OGTT, IRT (0 h, 1 h) levels and HOMR-IR in treatment groups were all reduced, meanwhile their protein and mRNA expression levels of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were obviously increased, and their protein and mRNA expression levels of β-arrestin-2 in the liver and skeletal muscle tissues were also markedly increased. It was suggested that the Fructus Mume formula and its separated prescription extracts could effectively improve insulin resistance in type 2 diabetic rats, which might be related to the up-regulated expression of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues, and β-arrestin-2 in the liver and skeletal muscle tissues.

Sweat chloride and immunoreactive trypsinogen in infants carrying two CFTR mutations and not affected by cystic fibrosis.

PubMed

Castellani, Carlo; Tridello, Gloria; Tamanini, Anna; Assael, Baroukh M

2017-07-01

Newborns with raised immunotrypsinogen levels who have non-pathological sweat chloride values and carry two cystic fibrosis transmembrane regulator ( CFTR ) mutations of which at least one is not acknowledged to be cystic fibrosis (CF)-causing are at risk of developing clinical manifestations consistent with CFTR-related disorders or even CF. It is not known whether newborns with similar genotypes and normal immunoreactive trypsinogen (IRT) may share the same risk. This study found that newborns with these characteristics and normal IRT have lower sweat chloride values than those with raised IRT (p=0.007). Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Infrared thermography for wood density estimation

NASA Astrophysics Data System (ADS)

López, Gamaliel; Basterra, Luis-Alfonso; Acuña, Luis

2018-03-01

Infrared thermography (IRT) is becoming a commonly used technique to non-destructively inspect and evaluate wood structures. Based on the radiation emitted by all objects, this technique enables the remote visualization of the surface temperature without making contact using a thermographic device. The process of transforming radiant energy into temperature depends on many parameters, and interpreting the results is usually complicated. However, some works have analyzed the operation of IRT and expanded its applications, as found in the latest literature. This work analyzes the effect of density on the thermodynamic behavior of timber to be determined by IRT. The cooling of various wood samples has been registered, and a statistical procedure that enables one to quantitatively estimate the density of timber has been designed. This procedure represents a new method to physically characterize this material.

Energetic electrons, hard x-ray emission and MHD activity studies in the IR-T1 tokamak.

PubMed

Agah, K Mikaili; Ghoranneviss, M; Elahi, A Salar

2015-01-01

Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons.

Thermographic Sensing For On-Line Industrial Control

NASA Astrophysics Data System (ADS)

Holmsten, Dag

1986-10-01

It is today's emergence of thermoelectrically cooled, highly accurate infrared linescanners and imaging systems that has definitely made on-line Infraread Thermography (IRT) possible. Specifically designed for continuous use, these scanners are equipped with dedicated software capable of monitoring and controlling highly complex thermodynamic situations. This paper will outline some possible implications of using IRT on-line by describing some uses of this technology in the steel-making (hot rolling) and automotive industries (machine-vision). A warning is also expressed that IRT technology not originally designed for automated applications e.g. high resolution, imaging systems, should not be directly applied to an on-line measurement situation without having its measurement resolution, accuracy and especially its repeatability, reliably proven. Some suitable testing procedures are briefly outlined at the end of the paper.

A Randomized, Placebo-Controlled Trial of Online Cognitive Behavioral Therapy for Chronic Insomnia Disorder Delivered via an Automated Media-Rich Web Application

PubMed Central

Espie, Colin A.; Kyle, Simon D.; Williams, Chris; Ong, Jason C.; Douglas, Neil J.; Hames, Peter; Brown, June S.L.

2012-01-01

Study Objectives: The internet provides a pervasive milieu for healthcare delivery. The purpose of this study was to determine the effectiveness of a novel web-based cognitive behavioral therapy (CBT) course delivered by an automated virtual therapist, when compared with a credible placebo; an approach required because web products may be intrinsically engaging, and vulnerable to placebo response. Design: Randomized, placebo-controlled trial comprising 3 arms: CBT, imagery relief therapy (IRT: placebo), treatment as usual (TAU). Setting: Online community of participants in the UK. Participants: One hundred sixty-four adults (120 F: [mean age 49y (18-78y)] meeting proposed DSM-5 criteria for Insomnia Disorder, randomly assigned to CBT (n = 55; 40 F), IRT placebo (n = 55; 42 F) or TAU (n = 54; 38 F). Interventions: CBT and IRT each comprised 6 online sessions delivered by an animated personal therapist, with automated web and email support. Participants also had access to a video library/back catalogue of session content and Wikipedia style articles. Online CBT users had access to a moderated social network/community of users. TAU comprised no restrictions on usual care and access to an online sleep diary. Measurements and Results: Major assessments at baseline, post-treatment, and at follow-up 8-weeks post-treatment; outcomes appraised by online sleep diaries and clinical status. On the primary endpoint of sleep efficiency (SE; total time asleep expressed as a percentage of the total time spent in bed), online CBT was associated with sustained improvement at post-treatment (+20%) relative to both TAU (+6%; d = 0.95) and IRT (+6%: d = 1.06), and at 8 weeks (+20%) relative to IRT (+7%: d = 1.00) and TAU (+9%: d = 0.69) These findings were mirrored across a range of sleep diary measures. Clinical benefits of CBT were evidenced by modest superiority over placebo on daytime outcomes (d = 0.23-0.37) and by substantial improved sleep-wake functioning on the Sleep Condition Indicator (range of d = 0.77-1.20). Three-quarters of CBT participants (76% [CBT] vs. 29% [IRT] and 18% [TAU]) completed treatment with SE > 80%, more than half (55% [CBT] vs. 17% [IRT] and 8% [TAU]) with SE > 85%, and over one-third (38% [CBT] vs. 6% [IRT] and 0% [TAU]) with SE > 90%; these improvements were largely maintained during follow-up. Conclusion: CBT delivered using a media-rich web application with automated support and a community forum is effective in improving the sleep and associated daytime functioning of adults with insomnia disorder. Clinical Trial Registration: ISRCTN – 44615689. Citation: Espie CA; Kyle SD; Williams C; Ong JC; Douglas NJ; Hames P; Brown JSL. A randomized, placebo-controlled trial of online cognitive behavioral therapy for chronic insomnia disorder delivered via an automated media-rich web application. SLEEP 2012;35(6):769-781. PMID:22654196

Analysis Test of Understanding of Vectors with the Three-Parameter Logistic Model of Item Response Theory and Item Response Curves Technique

ERIC Educational Resources Information Center

Rakkapao, Suttida; Prasitpong, Singha; Arayathanitkul, Kwan

2016-01-01

This study investigated the multiple-choice test of understanding of vectors (TUV), by applying item response theory (IRT). The difficulty, discriminatory, and guessing parameters of the TUV items were fit with the three-parameter logistic model of IRT, using the parscale program. The TUV ability is an ability parameter, here estimated assuming…

An Application of Unfolding and Cumulative Item Response Theory Models for Noncognitive Scaling: Examining the Assumptions and Applicability of the Generalized Graded Unfolding Model

ERIC Educational Resources Information Center

Sgammato, Adrienne N.

2009-01-01

This study examined the applicability of a relatively new unidimensional, unfolding item response theory (IRT) model called the generalized graded unfolding model (GGUM; Roberts, Donoghue, & Laughlin, 2000). A total of four scaling methods were applied. Two commonly used cumulative IRT models for polytomous data, the Partial Credit Model and…

Practical Implications of Test Dimensionality for Item Response Theory Calibration of the Medical College Admission Test. MCAT Monograph.

ERIC Educational Resources Information Center

Childs, Ruth A.; Oppler, Scott H.

The use of item response theory (IRT) in the Medical College Admission Test (MCAT) testing program has been limited. This study provides a basis for future IRT analyses of the MCAT by exploring the dimensionality of each of the MCAT's three multiple-choice test sections (Verbal Reasoning, Physical Sciences, and Biological Sciences) and the…

DIF Testing with an Empirical-Histogram Approximation of the Latent Density for Each Group

ERIC Educational Resources Information Center

Woods, Carol M.

2011-01-01

This research introduces, illustrates, and tests a variation of IRT-LR-DIF, called EH-DIF-2, in which the latent density for each group is estimated simultaneously with the item parameters as an empirical histogram (EH). IRT-LR-DIF is used to evaluate the degree to which items have different measurement properties for one group of people versus…

The Robustness of LOGIST and BILOG IRT Estimation Programs to Violations of Local Independence.

ERIC Educational Resources Information Center

Ackerman, Terry A.

One of the important underlying assumptions of all item response theory (IRT) models is that of local independence. This assumption requires that the response to an item on a test not be influenced by the response to any other items. This assumption is often taken for granted, with little or no scrutiny of the response process required to answer…

The Impact of Test Dimensionality, Common-Item Set Format, and Scale Linking Methods on Mixed-Format Test Equating

ERIC Educational Resources Information Center

Öztürk-Gübes, Nese; Kelecioglu, Hülya

2016-01-01

The purpose of this study was to examine the impact of dimensionality, common-item set format, and different scale linking methods on preserving equity property with mixed-format test equating. Item response theory (IRT) true-score equating (TSE) and IRT observed-score equating (OSE) methods were used under common-item nonequivalent groups design.…

Comparing Different Approaches of Bias Correction for Ability Estimation in IRT Models. Research Report. ETS RR-08-13

ERIC Educational Resources Information Center

Lee, Yi-Hsuan; Zhang, Jinming

2008-01-01

The method of maximum-likelihood is typically applied to item response theory (IRT) models when the ability parameter is estimated while conditioning on the true item parameters. In practice, the item parameters are unknown and need to be estimated first from a calibration sample. Lewis (1985) and Zhang and Lu (2007) proposed the expected response…

Assessing the Utility of Item Response Theory Models: Differential Item Functioning.

ERIC Educational Resources Information Center

Scheuneman, Janice Dowd

The current status of item response theory (IRT) is discussed. Several IRT methods exist for assessing whether an item is biased. Focus is on methods proposed by L. M. Rudner (1975), F. M. Lord (1977), D. Thissen et al. (1988) and R. L. Linn and D. Harnisch (1981). Rudner suggested a measure of the area lying between the two item characteristic…

A Note on Stochastic Ordering of the Latent Trait Using the Sum of Polytomous Item Scores

ERIC Educational Resources Information Center

van der Ark, L. Andries; Bergsma, Wicher P.

2010-01-01

In contrast to dichotomous item response theory (IRT) models, most well-known polytomous IRT models do not imply stochastic ordering of the latent trait by the total test score (SOL). This has been thought to make the ordering of respondents on the latent trait using the total test score questionable and throws doubt on the justifiability of using…

Comparing the Fit of Item Response Theory and Factor Analysis Models

ERIC Educational Resources Information Center

Maydeu-Olivares, Alberto; Cai, Li; Hernandez, Adolfo

2011-01-01

Linear factor analysis (FA) models can be reliably tested using test statistics based on residual covariances. We show that the same statistics can be used to reliably test the fit of item response theory (IRT) models for ordinal data (under some conditions). Hence, the fit of an FA model and of an IRT model to the same data set can now be…

A Comparison of the One-, the Modified Three-, and the Three-Parameter Item Response Theory Models in the Test Development Item Selection Process.

ERIC Educational Resources Information Center

Eignor, Daniel R.; Douglass, James B.

This paper attempts to provide some initial information about the use of a variety of item response theory (IRT) models in the item selection process; its purpose is to compare the information curves derived from the selection of items characterized by several different IRT models and their associated parameter estimation programs. These…

Does Preequating Work? An Investigation into a Preequated Testlet-Based College Placement Exam Using Postadministration Data. Research Report. ETS RR-12-12

ERIC Educational Resources Information Center

Gao, Rui; He, Wei; Ruan, Chunyi

2012-01-01

In this study, we investigated whether preequating results agree with equating results that are based on observed operational data (postequating) for a college placement program. Specifically, we examined the degree to which item response theory (IRT) true score preequating results agreed with those from IRT true score postequating and from…

An Information-Correction Method for Testlet-Based Test Analysis: From the Perspectives of Item Response Theory and Generalizability Theory. Research Report. ETS RR-17-27

ERIC Educational Resources Information Center

Li, Feifei

2017-01-01

An information-correction method for testlet-based tests is introduced. This method takes advantage of both generalizability theory (GT) and item response theory (IRT). The measurement error for the examinee proficiency parameter is often underestimated when a unidimensional conditional-independence IRT model is specified for a testlet dataset. By…

A Comparison of Three IRT Approaches to Examinee Ability Change Modeling in a Single-Group Anchor Test Design

ERIC Educational Resources Information Center

Paek, Insu; Park, Hyun-Jeong; Cai, Li; Chi, Eunlim

2014-01-01

Typically a longitudinal growth modeling based on item response theory (IRT) requires repeated measures data from a single group with the same test design. If operational or item exposure problems are present, the same test may not be employed to collect data for longitudinal analyses and tests at multiple time points are constructed with unique…

"We Freeze to Please": A History of NASA's Icing Research Tunnel and the Quest for Flight Safety

NASA Technical Reports Server (NTRS)

Leary, William M.

2002-01-01

The formation of ice on wings and other control surfaces of airplanes is one of the oldest and most vexing problems that aircraft engineers and scientists continue to face. While no easy, comprehensive answers exist, the staff at NASAs Icing Research Tunnel (IRT) at the Glenn Research Center in Cleveland has done pioneering work to make flight safer for experimental, commercial, and military customers. The National Advisory Committee for Aeronautics (NACA) initiated government research on aircraft icing in the 1930s at its Langley facility in Virginia. Icing research shifted to the NACA's Cleveland facility in the 1940s. Initially there was little focus on icing at either location, as these facilities were more concerned with aerodynamics and engine development. With several high-profile fatal crashes of air mail carriers, however, the NACA soon realized the need for a leading research facility devoted to icing prevention and removal. The IRT began operation in 1944 and, despite renovations and periodic attempts to shut it down, has continued to function productively for almost 60 years. In part because icing has proved so problematic over time, IRT researchers have been unusually open-minded in experimenting with a wide variety of substances, devices, and techniques. Early icing prevention experiments involved grease, pumping hot engine exhaust onto the wings, glycerin soap, mechanical and inflatable "boots," and even corn syrup. The IRT staff also looked abroad for ideas and later tried a German and Soviet technique of electromagnetism, to no avail. More recently, European polymer fluids have been more promising. The IRT even periodically had "amateur nights" in which a dentist's coating for children's teeth proved unequal to the demands of super-cooled water droplets blown at 100 miles per hour. Despite many research dead-ends, IRT researchers have achieved great success over the years. They have developed important computer models, such as the LEWICE software, and made significant contributions to prevent ice buildup on turbine-powered commercial aircraft, helicopters, and military planes.

Treatment and technical intervention time analysis of a robotic stereotactic radiotherapy system.

PubMed

Crop, F; Lacornerie, T; Szymczak, H; Felin, A; Bailleux, C; Mirabel, X; Lartigau, E

2014-02-01

The purpose of this study is to obtain a better operational knowledge of Stereotactic Body Radiotherapy (SBRT) treatments with CyberKnife(r). An analysis of both In-room Times (IRT) and technical interventions of 5 years of treatments was performed, during which more than 1600 patients were treated for various indications, including liver (21%), lung (29%), intracranial (13%), head and neck (11%) and prostate (7%). Technical interventions were recorded along with the time of the failure, time to the intervention, and the complexity and duration of the repair. Analyses of Time Between Failures (TBF) and Service Disrupting TBF(disr) were performed. Treatment time data and variability per indication and following different system upgrades were evaluated. Large variations of IRTs were found between indications, but also large variations for each indication. The combination of the time reduction Tool (using Iris(r)) and Improved Stop Handling was of major impact to shortening of treatment times. The first implementation of the Iris collimator alone did not lead to significantly shorter IRTs for us except during prostate treatments. This was mostly due to the addition at the same time of larger rotational compensation for prostate treatments (58 instead of 1.58). Significant differences of duration between the first fraction and following fractions of a treatment, representing the necessity of defining imaging parameters and explanation to patients, were found for liver (12 min) and lung treatments using Xsight(r) Spine (5 min). Liver and lung treatments represent the longest IRT's and involve the largest variability's in IRT. The malfunction rate of the system followed a Weibull distribution with the shape and scale parameters of 0.8 and 39.7. Mean TBF(disr) was 68 work hours. 60 to 80% of the service disrupting interventions were resolved within 30-60 min, 5% required external intervention and 30% occurred in the morning. The presented results can be applied in the evaluation of the required machine time in order to implement robotic radiosurgery for different indications. The analytical distributions of IRTs and technical interruptions can be used for simulations.

Measuring the ICF components of impairment, activity limitation and participation restriction: an item analysis using classical test theory and item response theory

PubMed Central

Pollard, Beth; Dixon, Diane; Dieppe, Paul; Johnston, Marie

2009-01-01

Background The International Classification of Functioning, Disability and Health (ICF) proposes three main health outcomes, Impairment (I), Activity Limitation (A) and Participation Restriction (P), but good measures of these constructs are needed The aim of this study was to use both Classical Test Theory (CTT) and Item Response Theory (IRT) methods to carry out an item analysis to improve measurement of these three components in patients having joint replacement surgery mainly for osteoarthritis (OA). Methods A geographical cohort of patients about to undergo lower limb joint replacement was invited to participate. Five hundred and twenty four patients completed ICF items that had been previously identified as measuring only a single ICF construct in patients with osteoarthritis. There were 13 I, 26 A and 20 P items. The SF-36 was used to explore the construct validity of the resultant I, A and P measures. The CTT and IRT analyses were run separately to identify items for inclusion or exclusion in the measurement of each construct. The results from both analyses were compared and contrasted. Results Overall, the item analysis resulted in the removal of 4 I items, 9 A items and 11 P items. CTT and IRT identified the same 14 items for removal, with CTT additionally excluding 3 items, and IRT a further 7 items. In a preliminary exploration of reliability and validity, the new measures appeared acceptable. Conclusion New measures were developed that reflect the ICF components of Impairment, Activity Limitation and Participation Restriction for patients with advanced arthritis. The resulting Aberdeen IAP measures (Ab-IAP) comprising I (Ab-I, 9 items), A (Ab-A, 17 items), and P (Ab-P, 9 items) met the criteria of conventional psychometric (CTT) analyses and the additional criteria (information and discrimination) of IRT. The use of both methods was more informative than the use of only one of these methods. Thus combining CTT and IRT appears to be a valuable tool in the development of measures. PMID:19422677

Effect of dobutamine on a Doppler echocardiographic index of combined systolic and diastolic performance.

PubMed

Harada, K; Tamura, M; Toyono, M; Yasuoka, K

2002-01-01

Dobutamine stress echocardiography has become accepted in the evaluation of cardiac functional reserve. Although the Doppler-derived index of combined systolic/diastolic myocardial performance (Tei index) has been reported to be easily obtainable and useful for predicting left ventricular performance, the effect of dobutamine on the Tei index has not been determined in children. To assess the effect of dobutamine on the Tei index, 8 patients who had undergone surgery for ventricular septal defect and 7 patients who had a history of Kawasaki disease were examined. Echocardiographic recordings were obtained before and after dobutamine infusion (5 microg/kg per minute). Variables measured were transmitral flow velocities (E, A, E/A), rate-corrected mean velocity of circumferential fiber shortening (rate-corrected Vcf), and IMP. We measured isovolumic contraction time (ICT), isovolumic relaxation time (IRT), and ejection time (ET) and then calculated the Tei index using the following formula: Tei index = (ICT + IRT)/ET. Dobutamine infusion increased rate-corrected Vcf (29%, p < 0.01), peak E (7%, p < 0.05), and peak A (13%, p < 0.05). E/A ratio did not change during dobutamine infusion. ET, ICT, and IRT were found to decrease during dobutamine infusion. The magnitude of the change in the ICT (-21%, p < 0.01) was greater than those in IRT (-12%, p < 0.01) and ET (-8%, p < 0.05). The decrease in Tei index (-16%, p < 0.01) resulted in a decrease in ICT/ET (-21%, p < 0.01) and a slight decrease in IRT/ET (-12%, p < 0.05). The Tei index has potential as a sensitive indicator of the effects of inotropic stimilation on global left ventricular function.

An Experimental and Numerical Study of Icing Effects on the Performance and Controllability of a Twin Engine Aircraft

NASA Technical Reports Server (NTRS)

Reehorst, A.; Chung, J.; Potapczuk, M.; Choo, Y.; Wright, W.; Langhals, T.

1999-01-01

In September 1997 the National Transportation Safety Board (NTSB) requested assistance from the NASA Lewis Research Center (LeRC) Icing Branch in the investigation of an aircraft accident that was suspected of being caused by ice contamination. In response to the request NASA agreed to perform an experimental and computational study. The main activities that NASA performed were LERC Icing Research Tunnel (IRT) testing to define ice shapes and 2-D Navier-Stokes analysis to determine the performance degradation that those ice shapes would have caused. An IRT test was conducted in January 1998. Most conditions for the test were based upon raw and derived data from the Flight Data Recorder (FDR) recovered from the accident and upon the current understanding of the Meteorological conditions near the accident. Using a two-dimensional Navier-Stokes code, the flow field and resultant lift and drag were calculated for the wing section with various ice shapes accreted in the IRT test. Before the final calculations could be performed extensive examinations of geometry smoothing and turbulence were conducted. The most significant finding of this effort is that several of the five-minute ice accretions generated in the IRT were found by the Navier-Stokes analysis to produce severe lift and drag degradation. The information generated by this study suggests a possible scenario for the kind of control upset recorded in the accident. Secondary findings were that the ice shapes accreted in the IRT were mostly limited to the protected pneumatic boot region of the wing and that during testing, activation of the pneumatic boots cleared most of the ice.

Using classical test theory, item response theory, and Rasch measurement theory to evaluate patient-reported outcome measures: a comparison of worked examples.

PubMed

Petrillo, Jennifer; Cano, Stefan J; McLeod, Lori D; Coon, Cheryl D

2015-01-01

To provide comparisons and a worked example of item- and scale-level evaluations based on three psychometric methods used in patient-reported outcome development-classical test theory (CTT), item response theory (IRT), and Rasch measurement theory (RMT)-in an analysis of the National Eye Institute Visual Functioning Questionnaire (VFQ-25). Baseline VFQ-25 data from 240 participants with diabetic macular edema from a randomized, double-masked, multicenter clinical trial were used to evaluate the VFQ at the total score level. CTT, RMT, and IRT evaluations were conducted, and results were assessed in a head-to-head comparison. Results were similar across the three methods, with IRT and RMT providing more detailed diagnostic information on how to improve the scale. CTT led to the identification of two problematic items that threaten the validity of the overall scale score, sets of redundant items, and skewed response categories. IRT and RMT additionally identified poor fit for one item, many locally dependent items, poor targeting, and disordering of over half the response categories. Selection of a psychometric approach depends on many factors. Researchers should justify their evaluation method and consider the intended audience. If the instrument is being developed for descriptive purposes and on a restricted budget, a cursory examination of the CTT-based psychometric properties may be all that is possible. In a high-stakes situation, such as the development of a patient-reported outcome instrument for consideration in pharmaceutical labeling, however, a thorough psychometric evaluation including IRT or RMT should be considered, with final item-level decisions made on the basis of both quantitative and qualitative results. Copyright © 2015. Published by Elsevier Inc.

Thermal Imaging Is a Noninvasive Alternative to PET/CT for Measurement of Brown Adipose Tissue Activity in Humans

PubMed Central

Law, James; Morris, David E.; Izzi-Engbeaya, Chioma; Salem, Victoria; Coello, Christopher; Robinson, Lindsay; Jayasinghe, Maduka; Scott, Rebecca; Gunn, Roger; Rabiner, Eugenii; Tan, Tricia; Dhillo, Waljit S.; Bloom, Stephen; Budge, Helen

2018-01-01

Obesity and its metabolic consequences are a major cause of morbidity and mortality. Brown adipose tissue (BAT) utilizes glucose and free fatty acids to produce heat, thereby increasing energy expenditure. Effective evaluation of human BAT stimulators is constrained by the current standard method of assessing BAT—PET/CT—as it requires exposure to high doses of ionizing radiation. Infrared thermography (IRT) is a potential noninvasive, safe alternative, although direct corroboration with PET/CT has not been established. Methods: IRT and 18F-FDG PET/CT data from 8 healthy men subjected to water-jacket cooling were directly compared. Thermal images were geometrically transformed to overlay PET/CT-derived maximum intensity projection (MIP) images from each subject, and the areas with the most intense temperature and glucose uptake within the supraclavicular regions were compared. Relationships between supraclavicular temperatures (TSCR) from IRT and the metabolic rate of glucose uptake (MR(gluc)) from PET/CT were determined. Results: Glucose uptake on MR(gluc)MIP was found to correlate positively with a change in TSCR relative to a reference region (r2 = 0.721; P = 0.008). Spatial overlap between areas of maximal MR(gluc)MIP and maximal TSCR was 29.5% ± 5.1%. Prolonged cooling, for 60 min, was associated with a further TSCR rise, compared with cooling for 10 min. Conclusion: The supraclavicular hotspot identified on IRT closely corresponded to the area of maximal uptake on PET/CT-derived MR(gluc)MIP images. Greater increases in relative TSCR were associated with raised glucose uptake. IRT should now be considered a suitable method for measuring BAT activation, especially in populations for whom PET/CT is not feasible, practical, or repeatable. PMID:28912148

Structural and photodynamic properties of the anti-cancer drug irinotecan in aqueous solutions of different pHs.

PubMed

di Nunzio, Maria Rosaria; Douhal, Yasmin; Organero, Juan Angel; Douhal, Abderrazzak

2018-05-23

This work reports on photophysical studies of the irinotecan (IRT) anti-cancer drug in water solutions of different acidities (pH = 1.11-9.46). We found that IRT co-exists as mono-cationic (C1), di-cationic (C2), or neutral (N) forms. The population of each prototropic species depends on the pH of the solution. At pH = 1.11-3.01, the C1 and C2 structures are stabilized. At pH = 7.00, the most populated species is C1, while at pH values larger than 9.46 the N form is the most stable species. In the 1.11-2.61 pH range, the C1* emission is efficiently quenched by protons to give rise to the emission from C2*. The dynamic quenching constant, KD, is ∼32 M-1. While the diffusion governs the rate of excited-state proton-transfer (ESPT) under these conditions, the reaction rate increases with the proton concentration. A two-step diffusive Debye-Smoluchowski model was applied at pH = 1.11-2.61 to describe the protonation of C1*. The ESPT time constants derived for C1* are 382 and 1720 ps at pH = 1.11 and 1.95, respectively. We found that one proton species is involved in the protonation of C1* to give C2*, in the analyzed acidic pH range. Under alkaline conditions (pH = 9.46), the N form is the most stable structure of IRT. These results indicate the influence of the pH of the medium on the structural and dynamical properties of IRT in water solution. They may help to provide a better understanding on the relationship between the structure and biological activity of IRT.

Impact of IRT item misfit on score estimates and severity classifications: an examination of PROMIS depression and pain interference item banks.

PubMed

Zhao, Yue

2017-03-01

In patient-reported outcome research that utilizes item response theory (IRT), using statistical significance tests to detect misfit is usually the focus of IRT model-data fit evaluations. However, such evaluations rarely address the impact/consequence of using misfitting items on the intended clinical applications. This study was designed to evaluate the impact of IRT item misfit on score estimates and severity classifications and to demonstrate a recommended process of model-fit evaluation. Using secondary data sources collected from the Patient-Reported Outcome Measurement Information System (PROMIS) wave 1 testing phase, analyses were conducted based on PROMIS depression (28 items; 782 cases) and pain interference (41 items; 845 cases) item banks. The identification of misfitting items was assessed using Orlando and Thissen's summed-score item-fit statistics and graphical displays. The impact of misfit was evaluated according to the agreement of both IRT-derived T-scores and severity classifications between inclusion and exclusion of misfitting items. The examination of the presence and impact of misfit suggested that item misfit had a negligible impact on the T-score estimates and severity classifications with the general population sample in the PROMIS depression and pain interference item banks, implying that the impact of item misfit was insignificant. Findings support the T-score estimates in the two item banks as robust against item misfit at both the group and individual levels and add confidence to the use of T-scores for severity diagnosis in the studied sample. Recommendations on approaches for identifying item misfit (statistical significance) and assessing the misfit impact (practical significance) are given.

www.common-metrics.org: a web application to estimate scores from different patient-reported outcome measures on a common scale.

PubMed

Fischer, H Felix; Rose, Matthias

2016-10-19

Recently, a growing number of Item-Response Theory (IRT) models has been published, which allow estimation of a common latent variable from data derived by different Patient Reported Outcomes (PROs). When using data from different PROs, direct estimation of the latent variable has some advantages over the use of sum score conversion tables. It requires substantial proficiency in the field of psychometrics to fit such models using contemporary IRT software. We developed a web application ( http://www.common-metrics.org ), which allows estimation of latent variable scores more easily using IRT models calibrating different measures on instrument independent scales. Currently, the application allows estimation using six different IRT models for Depression, Anxiety, and Physical Function. Based on published item parameters, users of the application can directly estimate latent trait estimates using expected a posteriori (EAP) for sum scores as well as for specific response patterns, Bayes modal (MAP), Weighted likelihood estimation (WLE) and Maximum likelihood (ML) methods and under three different prior distributions. The obtained estimates can be downloaded and analyzed using standard statistical software. This application enhances the usability of IRT modeling for researchers by allowing comparison of the latent trait estimates over different PROs, such as the Patient Health Questionnaire Depression (PHQ-9) and Anxiety (GAD-7) scales, the Center of Epidemiologic Studies Depression Scale (CES-D), the Beck Depression Inventory (BDI), PROMIS Anxiety and Depression Short Forms and others. Advantages of this approach include comparability of data derived with different measures and tolerance against missing values. The validity of the underlying models needs to be investigated in the future.

A new IRT-based standard setting method: application to eCat-listening.

PubMed

García, Pablo Eduardo; Abad, Francisco José; Olea, Julio; Aguado, David

2013-01-01

Criterion-referenced interpretations of tests are highly necessary, which usually involves the difficult task of establishing cut scores. Contrasting with other Item Response Theory (IRT)-based standard setting methods, a non-judgmental approach is proposed in this study, in which Item Characteristic Curve (ICC) transformations lead to the final cut scores. eCat-Listening, a computerized adaptive test for the evaluation of English Listening, was administered to 1,576 participants, and the proposed standard setting method was applied to classify them into the performance standards of the Common European Framework of Reference for Languages (CEFR). The results showed a classification closely related to relevant external measures of the English language domain, according to the CEFR. It is concluded that the proposed method is a practical and valid standard setting alternative for IRT-based tests interpretations.

Extending item response theory to online homework

NASA Astrophysics Data System (ADS)

Kortemeyer, Gerd

2014-06-01

Item response theory (IRT) becomes an increasingly important tool when analyzing "big data" gathered from online educational venues. However, the mechanism was originally developed in traditional exam settings, and several of its assumptions are infringed upon when deployed in the online realm. For a large-enrollment physics course for scientists and engineers, the study compares outcomes from IRT analyses of exam and homework data, and then proceeds to investigate the effects of each confounding factor introduced in the online realm. It is found that IRT yields the correct trends for learner ability and meaningful item parameters, yet overall agreement with exam data is moderate. It is also found that learner ability and item discrimination is robust over a wide range with respect to model assumptions and introduced noise. Item difficulty is also robust, but over a narrower range.

Wind tunnel evaluation of air-foil performance using simulated ice shapes

NASA Technical Reports Server (NTRS)

Bragg, M. B.; Zaguli, R. J.; Gregorek, G. M.

1982-01-01

A two-phase wind tunnel test was conducted in the 6 by 9 foot Icing Research Tunnel (IRT) at NASA Lewis Research Center to evaluate the effect of ice on the performance of a full scale general aviation wing. In the first IRT tests, rime and glaze shapes were carefully documented as functions of angle of attack and free stream conditions. Next, simulated ice shapes were constructed for two rime and two glaze shapes and used in the second IRT tunnel entry. The ice shapes and the clean airfoil were tapped to obtain surface pressures and a probe used to measure the wake characteristics. These data were recorded and processed, on-line, with a minicomputer/digital data acquisition system. The effect of both rime and glaze ice on the pressure distribution, Cl, Cd, and Cm are presented.

Nondestructive damage evaluation in ceramic matrix composites for aerospace applications.

PubMed

Dassios, Konstantinos G; Kordatos, Evangelos Z; Aggelis, Dimitrios G; Matikas, Theodore E

2013-01-01

Infrared thermography (IRT) and acoustic emission (AE) are the two major nondestructive methodologies for evaluating damage in ceramic matrix composites (CMCs) for aerospace applications. The two techniques are applied herein to assess and monitor damage formation and evolution in a SiC-fiber reinforced CMC loaded under cyclic and fatigue loading. The paper explains how IRT and AE can be used for the assessment of the material's performance under fatigue. IRT and AE parameters are specifically used for the characterization of the complex damage mechanisms that occur during CMC fracture, and they enable the identification of the micromechanical processes that control material failure, mainly crack formation and propagation. Additionally, these nondestructive parameters help in early prediction of the residual life of the material and in establishing the fatigue limit of materials rapidly and accurately.

Sodium sulfate crystallisation monitoring using IR thermography

NASA Astrophysics Data System (ADS)

Vazquez, P.; Thomachot-Schneider, C.; Mouhoubi, K.; Bodnar, J.-L.; Avdelidis, N. P.; Charles, D.; Benavente, D.

2018-03-01

In this work, the evaporation of sodium sulfate droplets with different concentrations and at different temperatures were studied using infrared thermography (IRT). IRT allows to detect the evaporation evolution, the crystal growth and for the first time, to observe in vivo the heat release related to sodium sulfate crystallisation. A detailed study revealed that dendritic Thenardite III crystals appeared at the edge of all the crystallised droplets, though they showed a fast increase of temperature related to crystallisation only when a hydrated phase crystallised also from the droplet. The observation of the heat of crystallisation is thus directly related to the supersaturation of the droplet and consequently to temperature. In addition, IRT detection is circumscribed by the location of crystallisation. The heat can be observed and measured only when the crystallisation occurs in the interface solution - air.

Icing Research Tunnel (IRT) Force Measurement System (FMS)

NASA Technical Reports Server (NTRS)

Roberts, Paul W.

2012-01-01

An Electronics Engineer at the Glenn Research Center (GRC), requested the NASA Engineering and Safety Center (NESC) provide technical support for an evaluation of the existing force measurement system (FMS) at the GRC's Icing Research Tunnel (IRT) with the intent of developing conceptual designs to improve the tunnel's force measurement capability in order to better meet test customer needs. This report contains the outcome of the NESC technical review.

Factor Models for Ordinal Variables With Covariate Effects on the Manifest and Latent Variables: A Comparison of LISREL and IRT Approaches

ERIC Educational Resources Information Center

Moustaki, Irini; Joreskog, Karl G.; Mavridis, Dimitris

2004-01-01

We consider a general type of model for analyzing ordinal variables with covariate effects and 2 approaches for analyzing data for such models, the item response theory (IRT) approach and the PRELIS-LISREL (PLA) approach. We compare these 2 approaches on the basis of 2 examples, 1 involving only covariate effects directly on the ordinal variables…

Interval timing under a behavioral microscope: Dissociating motivational and timing processes in fixed-interval performance.

PubMed

Daniels, Carter W; Sanabria, Federico

2017-03-01

The distribution of latencies and interresponse times (IRTs) of rats was compared between two fixed-interval (FI) schedules of food reinforcement (FI 30 s and FI 90 s), and between two levels of food deprivation. Computational modeling revealed that latencies and IRTs were well described by mixture probability distributions embodying two-state Markov chains. Analysis of these models revealed that only a subset of latencies is sensitive to the periodicity of reinforcement, and prefeeding only reduces the size of this subset. The distribution of IRTs suggests that behavior in FI schedules is organized in bouts that lengthen and ramp up in frequency with proximity to reinforcement. Prefeeding slowed down the lengthening of bouts and increased the time between bouts. When concatenated, latency and IRT models adequately reproduced sigmoidal FI response functions. These findings suggest that behavior in FI schedules fluctuates in and out of schedule control; an account of such fluctuation suggests that timing and motivation are dissociable components of FI performance. These mixture-distribution models also provide novel insights on the motivational, associative, and timing processes expressed in FI performance. These processes may be obscured, however, when performance in timing tasks is analyzed in terms of mean response rates.

The Isolation of Motivational, Motoric, and Schedule Effects on Operant Performance: A Modeling Approach

PubMed Central

Brackney, Ryan J; Cheung, Timothy H. C; Neisewander, Janet L; Sanabria, Federico

2011-01-01

Dissociating motoric and motivational effects of pharmacological manipulations on operant behavior is a substantial challenge. To address this problem, we applied a response-bout analysis to data from rats trained to lever press for sucrose on variable-interval (VI) schedules of reinforcement. Motoric, motivational, and schedule factors (effort requirement, deprivation level, and schedule requirements, respectively) were manipulated. Bout analysis found that interresponse times (IRTs) were described by a mixture of two exponential distributions, one characterizing IRTs within response bouts, another characterizing intervals between bouts. Increasing effort requirement lengthened the shortest IRT (the refractory period between responses). Adding a ratio requirement increased the length and density of response bouts. Both manipulations also decreased the bout-initiation rate. In contrast, food deprivation only increased the bout-initiation rate. Changes in the distribution of IRTs over time showed that responses during extinction were also emitted in bouts, and that the decrease in response rate was primarily due to progressively longer intervals between bouts. Taken together, these results suggest that changes in the refractory period indicate motoric effects, whereas selective alterations in bout initiation rate indicate incentive-motivational effects. These findings support the use of response-bout analyses to identify the influence of pharmacological manipulations on processes underlying operant performance. PMID:21765544

Measured performance of the heat exchanger in the NASA icing research tunnel under severe icing and dry-air conditions

NASA Technical Reports Server (NTRS)

Olsen, W.; Vanfossen, J.; Nussle, R.

1987-01-01

Measurements were made of the pressure drop and thermal perfomance of the unique refrigeration heat exchanger in the NASA Lewis Icing Research Tunnel (IRT) under severe icing and frosting conditions and also with dry air. This data will be useful to those planning to use or extend the capability of the IRT and other icing facilities (e.g., the Altitude Wind Tunnel-AWT). The IRT heat exchanger and refrigeration system is able to cool air passing through the test section down to at least a total temperature of -30 C (well below icing requirements), and usually up to -2 C. The system maintains a uniform temperature across the test section at all airspeeds, which is more difficult and time consuming at low airspeeds, at high temperatures, and on hot, humid days when the cooling towers are less efficient. The very small surfaces of the heat exchanger prevent any icing cloud droplets from passing through it and going through the tests section again. The IRT heat exchanger was originally designed not to be adversely affected by severe icing. During a worst-case icing test the heat exchanger iced up enough so that the temperature uniformaity was no worse than about +/- 1 deg C. The conclusion is that the heat exchanger design performs well.

Alternative Matching Scores to Control Type I Error of the Mantel-Haenszel Procedure for DIF in Dichotomously Scored Items Conforming to 3PL IRT and Nonparametric 4PBCB Models

ERIC Educational Resources Information Center

Monahan, Patrick O.; Ankenmann, Robert D.

2010-01-01

When the matching score is either less than perfectly reliable or not a sufficient statistic for determining latent proficiency in data conforming to item response theory (IRT) models, Type I error (TIE) inflation may occur for the Mantel-Haenszel (MH) procedure or any differential item functioning (DIF) procedure that matches on summed-item…

Effectiveness of Item Response Theory (IRT) Proficiency Estimation Methods under Adaptive Multistage Testing. Research Report. ETS RR-15-11

ERIC Educational Resources Information Center

Kim, Sooyeon; Moses, Tim; Yoo, Hanwook Henry

2015-01-01

The purpose of this inquiry was to investigate the effectiveness of item response theory (IRT) proficiency estimators in terms of estimation bias and error under multistage testing (MST). We chose a 2-stage MST design in which 1 adaptation to the examinees' ability levels takes place. It includes 4 modules (1 at Stage 1, 3 at Stage 2) and 3 paths…

An Investigation of the Performance of the Generalized S-X[superscript 2] Item-Fit Index for Polytomous IRT Models. ACT Research Report Series, 2007-1

ERIC Educational Resources Information Center

Kang, Taehoon; Chen, Troy T.

2007-01-01

Orlando and Thissen (2000, 2003) proposed an item-fit index, S-X[superscript 2], for dichotomous item response theory (IRT) models, which has performed better than traditional item-fit statistics such as Yen's (1981) Q[subscript 1] and McKinley and Mill's (1985) G[superscript 2]. This study extends the utility of S-X[superscript 2] to polytomous…

The Army FAO Training Program: Time to Break More Glass

DTIC Science & Technology

2013-03-01

these five countries, English is the co-national language in the Philippines, a strong second language in Malaysia , and the second language and growing...advanced language studies and develop in-depth knowledge of the region through a program of travel, research, and self -study.” While IRT succeeds in...in providing advanced language training. Furthermore, most IRT FAOs conduct little research, and “ self -study”, when conducted, normally equates to

RADON LEVELS AND ЕQUIVALENT DOSE RATES AT THE IRT-SOFIA RESEARCH REACTOR SITE.

PubMed

Krezhov, Kiril; Mladenov, Aleksander; Dimitrov, Dobromir

2018-06-11

Results from radon measurements by active sampling of indoor air in the buildings within the Nuclear Scientific Experimental and Educational Centre (NSEEC) protected site at the Institute for Nuclear Research and Nuclear Energy (INRNE) are presented. The inspected buildings included in this report are the IRT research reactor structure and several auxiliary formations wherein the laundry facilities and the gamma irradiator GOU-1 (60Co source) are installed as well as the Central Alarm Station (CAS) premises. Besides the reactor hall and the primary cooling loop area, special attention was given to the premises of the First Class Radiochemical Laboratory in the IRT reactor basement. Determination of radon concentration distribution in the premises of the constructions within the site is an important part of radiation surveillance during the operation and maintenance of the NSEEC facilities as well as for their involvement in the educational activities at INRNE.

Overview of the Icing and Flow Quality Improvements Program for the NASA Glenn Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Irvine, Thomas B.; Kevdzija, Susan L.; Sheldon, David W.; Spera, David A.

2001-01-01

Major upgrades were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research Tunnel (IRT) at the NASA Glenn Research Center. These included replacement of the electronic controls for the variable-speed drive motor, replacement of the heat exchanger, complete replacement and enlargement of the leg of the tunnel containing the new heat-exchanger, the addition of flow-expanding and flow-contracting turning vanes upstream and downstream of the heat exchanger, respectively, and the addition of fan outlet guide vanes (OGV's). This paper describes the rationale behind this latest program of IRT upgrades and the program's requirements and goals. An overview is given of the scope of work undertaken by the design and construction contractors, the scale-model IRT (SMIRT) design verification program, the comprehensive reactivation test program initiated upon completion of construction, and the overall management approach followed.

Extending LMS to Support IRT-Based Assessment Test Calibration

NASA Astrophysics Data System (ADS)

Fotaris, Panagiotis; Mastoras, Theodoros; Mavridis, Ioannis; Manitsaris, Athanasios

Developing unambiguous and challenging assessment material for measuring educational attainment is a time-consuming, labor-intensive process. As a result Computer Aided Assessment (CAA) tools are becoming widely adopted in academic environments in an effort to improve the assessment quality and deliver reliable results of examinee performance. This paper introduces a methodological and architectural framework which embeds a CAA tool in a Learning Management System (LMS) so as to assist test developers in refining items to constitute assessment tests. An Item Response Theory (IRT) based analysis is applied to a dynamic assessment profile provided by the LMS. Test developers define a set of validity rules for the statistical indices given by the IRT analysis. By applying those rules, the LMS can detect items with various discrepancies which are then flagged for review of their content. Repeatedly executing the aforementioned procedure can improve the overall efficiency of the testing process.

High-order noise analysis for low dose iterative image reconstruction methods: ASIR, IRIS, and MBAI

NASA Astrophysics Data System (ADS)

Do, Synho; Singh, Sarabjeet; Kalra, Mannudeep K.; Karl, W. Clem; Brady, Thomas J.; Pien, Homer

2011-03-01

Iterative reconstruction techniques (IRTs) has been shown to suppress noise significantly in low dose CT imaging. However, medical doctors hesitate to accept this new technology because visual impression of IRT images are different from full-dose filtered back-projection (FBP) images. Most common noise measurements such as the mean and standard deviation of homogeneous region in the image that do not provide sufficient characterization of noise statistics when probability density function becomes non-Gaussian. In this study, we measure L-moments of intensity values of images acquired at 10% of normal dose and reconstructed by IRT methods of two state-of-art clinical scanners (i.e., GE HDCT and Siemens DSCT flash) by keeping dosage level identical to each other. The high- and low-dose scans (i.e., 10% of high dose) were acquired from each scanner and L-moments of noise patches were calculated for the comparison.

Infrared thermography based on artificial intelligence as a screening method for carpal tunnel syndrome diagnosis.

PubMed

Jesensek Papez, B; Palfy, M; Mertik, M; Turk, Z

2009-01-01

This study further evaluated a computer-based infrared thermography (IRT) system, which employs artificial neural networks for the diagnosis of carpal tunnel syndrome (CTS) using a large database of 502 thermal images of the dorsal and palmar side of 132 healthy and 119 pathological hands. It confirmed the hypothesis that the dorsal side of the hand is of greater importance than the palmar side when diagnosing CTS thermographically. Using this method it was possible correctly to classify 72.2% of all hands (healthy and pathological) based on dorsal images and > 80% of hands when only severely affected and healthy hands were considered. Compared with the gold standard electromyographic diagnosis of CTS, IRT cannot be recommended as an adequate diagnostic tool when exact severity level diagnosis is required, however we conclude that IRT could be used as a screening tool for severe cases in populations with high ergonomic risk factors of CTS.

A Review of the Effects on IRT Item Parameter Estimates with a Focus on Misbehaving Common Items in Test Equating

PubMed Central

Michaelides, Michalis P.

2010-01-01

Many studies have investigated the topic of change or drift in item parameter estimates in the context of item response theory (IRT). Content effects, such as instructional variation and curricular emphasis, as well as context effects, such as the wording, position, or exposure of an item have been found to impact item parameter estimates. The issue becomes more critical when items with estimates exhibiting differential behavior across test administrations are used as common for deriving equating transformations. This paper reviews the types of effects on IRT item parameter estimates and focuses on the impact of misbehaving or aberrant common items on equating transformations. Implications relating to test validity and the judgmental nature of the decision to keep or discard aberrant common items are discussed, with recommendations for future research into more informed and formal ways of dealing with misbehaving common items. PMID:21833230

A Review of the Effects on IRT Item Parameter Estimates with a Focus on Misbehaving Common Items in Test Equating.

PubMed

Michaelides, Michalis P

2010-01-01

Many studies have investigated the topic of change or drift in item parameter estimates in the context of item response theory (IRT). Content effects, such as instructional variation and curricular emphasis, as well as context effects, such as the wording, position, or exposure of an item have been found to impact item parameter estimates. The issue becomes more critical when items with estimates exhibiting differential behavior across test administrations are used as common for deriving equating transformations. This paper reviews the types of effects on IRT item parameter estimates and focuses on the impact of misbehaving or aberrant common items on equating transformations. Implications relating to test validity and the judgmental nature of the decision to keep or discard aberrant common items are discussed, with recommendations for future research into more informed and formal ways of dealing with misbehaving common items.

Ethylene response factor AtERF72 negatively regulates Arabidopsis thaliana response to iron deficiency.

PubMed

Liu, Wei; Li, Qiwei; Wang, Yi; Wu, Ting; Yang, Yafei; Zhang, Xinzhong; Han, Zhenhai; Xu, Xuefeng

2017-09-23

Ethylene regulates the plant's response to stress caused by iron (Fe) deficiency. However, specific roles of ERF proteins in response to Fe deficiency remain poorly understood. Here, we investigated the role of ERF72 in response to iron deficiency in Arabidopsis thaliana. In this study, the levels of the ethylene response factor AtERF72 increased in leaves and roots induced under the iron deficient conditions. erf72 mutant plants showed increased growth compared to wild type (WT) when grown in iron deficient medium for 5 d. erf72 mutants had increased root H + velocity and the ferric reductase activity, and increase in the expression of the iron deficiency response genes iron-regulated transporter 1 (IRT1) and H + -ATPase (HA2) levels in iron deficient conditions. Compared to WT plants, erf72 mutants retained healthy chloroplast structure with significantly higher Fe and Mg content, and decreased chlorophyll degradation gene pheophorbide a oxygenase (PAO) and chlorophyllase (CLH1) expression when grown in iron deficient media. Yeast one-hybrid analysis showed that ERF72 could directly bind to the promoter regions of iron deficiency responses genes IRT1, HA2 and CLH1. Based on our results, we suggest that ethylene released from plants under iron deficiency stress can activate the expression of ERF72, which responds to iron deficiency in the negative regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

Integration of Infrared Thermography and Photogrammetric Surveying of Built Landscape

NASA Astrophysics Data System (ADS)

Scaioni, M.; Rosina, E.; L'Erario, A.; Dìaz-Vilariño, L.

2017-05-01

The thermal analysis of buildings represents a key-step for reduction of energy consumption, also in the case of Cultural Heritage. Here the complexity of the constructions and the adopted materials might require special analysis and tailored solutions. Infrared Thermography (IRT) is an important non-destructive investigation technique that may aid in the thermal analysis of buildings. The paper reports the application of IRT on a listed building, belonging to the Cultural Heritage and to a residential one, as a demonstration that IRT is a suitable and convenient tool for analysing the existing buildings. The purposes of the analysis are the assessment of the damages and energy efficiency of the building envelope. Since in many cases the complex geometry of historic constructions may involve the thermal analysis, the integration of IRT and accurate 3D models were developed during the latest years. Here authors propose a solution based on the up-to-date photogrammetric solutions for purely image-based 3D modelling, including automatic image orientation/sensor calibration using Structure-from-Motion and dense matching. Thus, an almost fully automatic pipeline for the generation of accurate 3D models showing the temperatures on a building skin in a realistic manner is described, where the only manual task is given by the measurement of a few common points for co-registration of RGB and IR photogrammetric projects.

What are the appropriate methods for analyzing patient-reported outcomes in randomized trials when data are missing?

PubMed

Hamel, J F; Sebille, V; Le Neel, T; Kubis, G; Boyer, F C; Hardouin, J B

2017-12-01

Subjective health measurements using Patient Reported Outcomes (PRO) are increasingly used in randomized trials, particularly for patient groups comparisons. Two main types of analytical strategies can be used for such data: Classical Test Theory (CTT) and Item Response Theory models (IRT). These two strategies display very similar characteristics when data are complete, but in the common case when data are missing, whether IRT or CTT would be the most appropriate remains unknown and was investigated using simulations. We simulated PRO data such as quality of life data. Missing responses to items were simulated as being completely random, depending on an observable covariate or on an unobserved latent trait. The considered CTT-based methods allowed comparing scores using complete-case analysis, personal mean imputations or multiple-imputations based on a two-way procedure. The IRT-based method was the Wald test on a Rasch model including a group covariate. The IRT-based method and the multiple-imputations-based method for CTT displayed the highest observed power and were the only unbiased method whatever the kind of missing data. Online software and Stata® modules compatibles with the innate mi impute suite are provided for performing such analyses. Traditional procedures (listwise deletion and personal mean imputations) should be avoided, due to inevitable problems of biases and lack of power.

New scoring methodology improves the sensitivity of the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) in clinical trials.

PubMed

Verma, Nishant; Beretvas, S Natasha; Pascual, Belen; Masdeu, Joseph C; Markey, Mia K

2015-11-12

As currently used, the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) has low sensitivity for measuring Alzheimer's disease progression in clinical trials. A major reason behind the low sensitivity is its sub-optimal scoring methodology, which can be improved to obtain better sensitivity. Using item response theory, we developed a new scoring methodology (ADAS-CogIRT) for the ADAS-Cog, which addresses several major limitations of the current scoring methodology. The sensitivity of the ADAS-CogIRT methodology was evaluated using clinical trial simulations as well as a negative clinical trial, which had shown an evidence of a treatment effect. The ADAS-Cog was found to measure impairment in three cognitive domains of memory, language, and praxis. The ADAS-CogIRT methodology required significantly fewer patients and shorter trial durations as compared to the current scoring methodology when both were evaluated in simulated clinical trials. When validated on data from a real clinical trial, the ADAS-CogIRT methodology had higher sensitivity than the current scoring methodology in detecting the treatment effect. The proposed scoring methodology significantly improves the sensitivity of the ADAS-Cog in measuring progression of cognitive impairment in clinical trials focused in the mild-to-moderate Alzheimer's disease stage. This provides a boost to the efficiency of clinical trials requiring fewer patients and shorter durations for investigating disease-modifying treatments.

Doppler-derived myocardial performance index in patients with impaired left ventricular relaxation and preserved systolic function.

PubMed

Fernandes, José Maria G; Rivera, Ivan Romero; de Oliveira Romão, Benício; Mendonça, Maria Alayde; Vasconcelos, Miriam Lira Castro; Carvalho, Antônio Carlos; Campos, Orlando; De Paola, Angelo Amato V; Moisés, Valdir A

2009-09-01

The Doppler-derived myocardial performance index (MPI) has been used in the evaluation of left ventricular (LV) function in several diseases. In patients with isolated diastolic dysfunction, the diagnostic utility of this index remains unclear. The aim of this study was to determine the diagnostic utility of MPI in patients with systemic hypertension, impaired LV relaxation, and normal ejection fraction. Thirty hypertensive patients with impaired LV relaxation were compared to 30 control subjects. MPI and its components, isovolumetric relaxation time (IRT), isovolumetric contraction time (ICT), and the ejection time (ET), were measured from LV outflow and mitral inflow Doppler velocity profiles. MPI was higher in patients than in control subjects (0.45 +/- 0.13 vs 0.37 +/- 0.07 P < 0.0029). The increase in MPI was due to the prolongation of IRT without significant change of ICT and ET. MPI cutoff value of > or =0.40 identified impaired LV relaxation with a sensitivity of 63% and specificity of 70% while an IRT >94 ms had a sensitivity of 67% and specificity of 80%. Multivariate analysis identified relative wall thickness, mitral early filling wave velocity (E), and systolic myocardial velocity (Sm) as independent predictors of MPI in patients with hypertension. MPI was increase in patients with hypertension, diastolic dysfunction, and normal ejection fraction but was not superior to IRT to detect impaired LV relaxation.

An Item Response Theory Analysis of DSM–IV Diagnostic Criteria for Personality Disorders: Findings From the National Epidemiologic Survey on Alcohol and Related Conditions

PubMed Central

Harford, Thomas C.; Chen, Chiung M.; Saha, Tulshi D.; Smith, Sharon M.; Hasin, Deborah S.; Grant, Bridget F.

2013-01-01

The purpose of this study was to evaluate the psychometric properties of DSM–IV symptom criteria for assessing personality disorders (PDs) in a national population and to compare variations in proposed symptom coding for social and/or occupational dysfunction. Data were obtained from a total sample of 34,653 respondents from Waves 1 and 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). For each personality disorder, confirmatory factor analysis (CFA) established a 1-factor latent factor structure for the respective symptom criteria. A 2-parameter item response theory (IRT) model was applied to the symptom criteria for each PD to assess the probabilities of symptom item endorsements across different values of the underlying trait (latent factor). Findings were compared with a separate IRT model using an alternative coding of symptom criteria that requires distress/impairment to be related to each criterion. The CFAs yielded a good fit for a single underlying latent dimension for each PD. Findings from the IRT indicated that DSM–IV PD symptom criteria are clustered in the moderate to severe range of the underlying latent dimension for each PD and are peaked, indicating high measurement precision only within a narrow range of the underlying trait and lower measurement precision at lower and higher levels of severity. Compared with the NESARC symptom coding, the IRT results for the alternative symptom coding are shifted toward the more severe range of the latent trait but generally have lower measurement precision for each PD. The IRT findings provide support for a reliable assessment of each PD for both NESARC and alternative coding for distress/impairment. The use of symptom dysfunction for each criterion, however, raises a number of issues and implications for the DSM-5 revision currently proposed for Axis II disorders (American Psychiatric Association, 2010). PMID:22449066

Use of infrared thermography to assess the influence of high environmental temperature on rabbits.

PubMed

de Lima, V; Piles, M; Rafel, O; López-Béjar, M; Ramón, J; Velarde, A; Dalmau, A

2013-10-01

The aim of this work was to ascertain if infrared thermography (IRT) can be used on rabbits to assess differences in surface body temperature when they are subjected to two different environmental temperatures outside the comfort zone. Rabbits housed in room A were maintained at a temperature of below 30°C and rabbits in room B at a temperature of above 32°C for a year. Faeces were collected six times during the year to assess stress by means of faecal cortisol metabolites (FCM). The assessment of IRT was carried out to assess maximum and minimum temperatures on the eyes, nose and ears. FCM concentration was higher in room B than A, to confirm that stress conditions were higher in room B. Significant differences in IRT were found between the animals housed in both rooms. It was observed that it was more difficult for animals from room B to maintain a regular heat loss. Although all the body zones used to assess temperature with IRT gave statistical differences, the correlations found between the eyes, nose and ears were moderate, suggesting that they were giving different information. In addition, differences up to 3.36°C were found in the eye temperature of rabbits housed in the same room, with a clear effect of their position in relation to extractors and heating equipments. Therefore, IRT could be a good tool to assess heat stress in animals housed on typical rabbit farm buildings, giving a measure of how the animal is perceiving a combination of humidity, temperature and ventilation. Some face areas were better for analysing images. Minimum temperature on eyes and temperatures on nose are suggested to assess heat losses and critical areas of the farm for heat stress in rabbits. Copyright © 2013 Elsevier Ltd. All rights reserved.

Reductions in ambulatory blood pressure in young normotensive men and women after isometric resistance training and its relationship with cardiovascular reactivity.

PubMed

Somani, Yasina; Baross, Anthony; Levy, Phillip; Zinszer, Kate; Milne, Kevin; Swaine, Ian; McGowan, Cheri

2017-02-01

There has been very little published work exploring the comparative effects of isometric resistance training (IRT) on blood pressure (BP) in men and women. Most of the previously published work has involved men and used resting BP as the primary outcome variable. Early evidence suggests that IRT is particularly effective in older women and has a positive influence on ambulatory BP, a better predictor of disease risk. With the WHO now placing global emphasis on the primary prevention of hypertension, the goals of this proof-of-concept study were to (i) examine whether sex differences exist in the ambulatory BP-lowering effects of IRT in young, normotensive men and women and (ii) determine whether these reductions can be predicted by simple laboratory stress tasks (a 2-min sustained isometric contraction and a math task involving subtracting a two-digit number from a series of numbers). There were no differences in the IRT-induced reductions in 24-h (men: Δ4 mmHg, women: Δ4 mmHg), daytime (men: Δ3 mmHg, women: Δ4 mmHg), or night-time (men: Δ4 mmHg, women: Δ3 mmHg) ambulatory BP in men (n=13) and women (n=11) (P<0.05) and these changes were not associated with systolic BP reactivity to either stress task (all P>0.05). Our data suggest that lower ambulatory BP can be achieved, to a similar magnitude in young healthy women as well as men, with IRT; however, the BP-lowering effectiveness cannot be predicted by systolic BP reactivity. Taken together, this work heralds a potentially novel approach to the primary prevention of hypertension in both men and women and warrants further investigation in a larger clinical outcome trial.

Modified release terbutaline (SKP1052) for hypoglycaemia prevention: a proof-of-concept study in people with type 1 diabetes mellitus.

PubMed

Nosek, L; Cardot, J-M; Owens, D R; Ibarra, P; Bagate, K; Vergnault, G; Kaiser, K; Fischer, A; Heise, T

2012-12-01

In this randomized, single blind, cross-over study 2.5 mg and 5 mg of the modified-release terbutaline formulation (SKP-1052) were compared with conventional immediate-release terbutaline (IRT, 5 mg) and placebo on overnight blood glucose (BG) and hypoglycaemia in 30 subjects with type 1 diabetes mellitus. Subjects received subcutaneous injections of insulin glargine (individualized doses) before dinner. SKP-1052, IRT or placebo was administered around 21:00 hours. BG and terbutaline concentrations were monitored overnight for 10 h post-dosing. Endpoints comprised of the nadir BG (BGn 0-10 h, primary endpoint), mean overnight BG (BGmean), morning BG (BGmorning) and hypoglycaemia rates as well as pharmacokinetic (PK) endpoints. SKP-1052 delayed release of terbutaline by 2 h [PK-tmax (mean ± SD) 5.0 ± 2.1 h (2.5 mg) and 4.7 ± 1.7 h (5 mg) vs. 2.6 ± 1.3 h with IRT, p < 0.01, respectively]. Compared with placebo, no significant differences were observed for BGn 0-10 h across treatments, but both 5 mg formulations showed less hypoglycaemic events [10 (IRT), 16 (SKP-1052) vs. 33], higher BGmean (120, 114 and 95 mg/dl) and BGmorning (126, 126 and 101 mg/dl, all comparisons p < 0.05 vs. placebo). Numerically higher BG-levels between 3 and 8 h post-dosing were observed with 2.5 mg SKP-1052 vs. placebo. Compared with IRT SKP-1052 delays release of terbutaline. 2.5 mg SKP-1052 led to numerically higher BG 3 to 8 h post-dose without fasting hyperglycaemia while 5 mg SKP-1052 resulted in fasting hyperglycaemia vs. placebo. Future studies will investigate optimized doses of SKP-1052 for nocturnal hypoglycaemia prevention. © 2012 Blackwell Publishing Ltd.

Improvements to the Total Temperature Calibration of the NASA Glenn Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Arrington, E. Allen; Gonsalez, Jose C.

2005-01-01

The ability to accurately set repeatable total temperature conditions is critical for collecting quality icing condition data, particularly near freezing conditions. As part of efforts to continually improve data quality in the NASA Glenn Icing Research Tunnel (IRT), new facility instrumentation and new calibration hardware for total temperature measurement were installed and new operational techniques were developed and implemented. This paper focuses on the improvements made in the calibration of total temperature in the IRT.

New tests of the common calibration context for ISO, IRTS, and MSX

NASA Technical Reports Server (NTRS)

Cohen, Martin

1997-01-01

The work carried out in order to test, verify and validate the accuracy of the calibration spectra provided to the Infrared Space Observatory (ISO), to the Infrared Telescope in Space (IRTS) and to the Midcourse Space Experiment (MSX) for external calibration support of instruments, is reviewed. The techniques, used to vindicate the accuracy of the absolute spectra, are discussed. The work planned for comparing far infrared spectra of Mars and some of the bright stellar calibrators with long wavelength spectrometer data are summarized.

Impact of Transmammary-Delivered Meloxicam on Biomarkers of Pain and Distress in Piglets after Castration and Tail Docking

PubMed Central

Bates, Jessica L.; Karriker, Locke A.; Stock, Matthew L.; Pertzborn, Kelly M.; Baldwin, Luke G.; Wulf, Larry W.; Lee, C. J.; Wang, Chong; Coetzee, Johann F.

2014-01-01

To investigate a novel route for providing analgesia to processed piglets via transmammary drug delivery, meloxicam was administered orally to sows after farrowing. The objectives of the study were to demonstrate meloxicam transfer from sows to piglets via milk and to describe the analgesic effects in piglets after processing through assessment of pain biomarkers and infrared thermography (IRT). Ten sows received either meloxicam (30 mg/kg) (n = 5) or whey protein (placebo) (n = 5) in their daily feedings, starting four days after farrowing and continuing for three consecutive days. During this period, blood and milk samples were collected at 12-hour intervals. On Day 5 after farrowing, three boars and three gilts from each litter were castrated or sham castrated, tail docked, and administered an iron injection. Piglet blood samples were collected immediately before processing and at predetermined times over an 84-hour period. IRT images were captured at each piglet blood collection point. Plasma was tested to confirm meloxicam concentrations using a validated high-performance liquid chromatography-mass spectrometry method. Meloxicam was detected in all piglets nursing on medicated sows at each time point, and the mean (± standard error of the mean) meloxicam concentration at castration was 568.9±105.8 ng/mL. Furthermore, ex-vivo prostaglandin E2 (PGE2) synthesis inhibition was greater in piglets from treated sows compared to controls (p = 0.0059). There was a time-by-treatment interaction for plasma cortisol (p = 0.0009), with meloxicam-treated piglets demonstrating lower cortisol concentrations than control piglets for 10 hours after castration. No differences in mean plasma substance P concentrations between treatment groups were observed (p = 0.67). Lower cranial skin temperatures on IRT were observed in placebo compared to meloxicam-treated piglets (p = 0.015). This study demonstrates the successful transfer of meloxicam from sows to piglets through milk and corresponding analgesia after processing, as evidenced by a decrease in cortisol and PGE2 levels and maintenance of cranial skin temperature. PMID:25437866

Harmonizing Measures of Cognitive Performance Across International Surveys of Aging Using Item Response Theory.

PubMed

Chan, Kitty S; Gross, Alden L; Pezzin, Liliana E; Brandt, Jason; Kasper, Judith D

2015-12-01

To harmonize measures of cognitive performance using item response theory (IRT) across two international aging studies. Data for persons ≥65 years from the Health and Retirement Study (HRS, N = 9,471) and the English Longitudinal Study of Aging (ELSA, N = 5,444). Cognitive performance measures varied (HRS fielded 25, ELSA 13); 9 were in common. Measurement precision was examined for IRT scores based on (a) common items, (b) common items adjusted for differential item functioning (DIF), and (c) DIF-adjusted all items. Three common items (day of date, immediate word recall, and delayed word recall) demonstrated DIF by survey. Adding survey-specific items improved precision but mainly for HRS respondents at lower cognitive levels. IRT offers a feasible strategy for harmonizing cognitive performance measures across other surveys and for other multi-item constructs of interest in studies of aging. Practical implications depend on sample distribution and the difficulty mix of in-common and survey-specific items. © The Author(s) 2015.

Psychometric properties of the Global Operative Assessment of Laparoscopic Skills (GOALS) using item response theory.

PubMed

Watanabe, Yusuke; Madani, Amin; Ito, Yoichi M; Bilgic, Elif; McKendy, Katherine M; Feldman, Liane S; Fried, Gerald M; Vassiliou, Melina C

2017-02-01

The extent to which each item assessed using the Global Operative Assessment of Laparoscopic Skills (GOALS) contributes to the total score remains unknown. The purpose of this study was to evaluate the level of difficulty and discriminative ability of each of the 5 GOALS items using item response theory (IRT). A total of 396 GOALS assessments for a variety of laparoscopic procedures over a 12-year time period were included. Threshold parameters of item difficulty and discrimination power were estimated for each item using IRT. The higher slope parameters seen with "bimanual dexterity" and "efficiency" are indicative of greater discriminative ability than "depth perception", "tissue handling", and "autonomy". IRT psychometric analysis indicates that the 5 GOALS items do not demonstrate uniform difficulty and discriminative power, suggesting that they should not be scored equally. "Bimanual dexterity" and "efficiency" seem to have stronger discrimination. Weighted scores based on these findings could improve the accuracy of assessing individual laparoscopic skills. Copyright © 2016 Elsevier Inc. All rights reserved.

Using Item Response Theory to Evaluate LSCI Learning Gains

NASA Astrophysics Data System (ADS)

Schlingman, Wayne M.; Prather, E. E.; Collaboration of Astronomy Teaching Scholars CATS

2012-01-01

Analyzing the data from the recent national study using the Light and Spectroscopy Concept Inventory (LSCI), this project uses Item Response Theory (IRT) to investigate the learning gains of students as measured by the LSCI. IRT provides a theoretical model to generate parameters accounting for students’ abilities. We use IRT to measure changes in students’ abilities to reason about light from pre- to post-instruction. Changes in students’ abilities are compared by classroom to better understand the learning that is taking place in classrooms across the country. We compare the average change in ability for each classroom to the Interactivity Assessment Score (IAS) to provide further insight into the prior results presented from this data set. This material is based upon work supported by the National Science Foundation under Grant No. 0715517, a CCLI Phase III Grant for the Collaboration of Astronomy Teaching Scholars (CATS). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frybort, Jan

A critical experiment is a standard part of training of students at the Training Reactor VR-1 operated within the Faculty of Nuclear Sciences and Physical Engineering at the Czech Technical University in Prague. In autumn 2005 the HEU fuel IRT-3M with enrichment 36 % {sup 235}U was replaced by the LEU fuel IRT-4M with enrichment 19.7 % {sup 235}U. The fuel replacement at the VR-1 Reactor is a part of an international program RERTR. This Paper presents basic information about preparation for the fuel replacement and approaching of the first critical state with the new zone configuration C1 which replacedmore » B1 core with the old IRT-3M fuel. The whole process was carried out according to the Czech law and the relevant international recommendations. The experience with the VR-1 operation confirms the assumption that the C1 core configuration will be suitable from the point of view of the reactivity balance for the long term safe operation of the Training Reactor VR-1. (author)« less

Metastable Superconductivity in Two-Dimensional IrTe2 Crystals.

PubMed

Yoshida, Masaro; Kudo, Kazutaka; Nohara, Minoru; Iwasa, Yoshihiro

2018-05-09

Two-dimensional (2D) materials exhibit unusual physical and chemical properties that are attributed to the thinning-induced modification of their electronic band structure. Recently, reduced thickness was found to dramatically impact not only the static electronic structure, but also the dynamic ordering kinetics. The ordering kinetics of first-order phase transitions becomes significantly slowed with decreasing thickness, and metastable supercooled states can be realized by thinning alone. We therefore focus on layered iridium ditelluride (IrTe 2 ), a charge-ordering system that is transformed into a superconductor by suppressing its first-order transition. Here, we discovered a persistent superconducting zero-resistance state in mechanically exfoliated IrTe 2 thin flakes. The maximum superconducting critical temperature ( T c ) was identical to that which is chemically optimized, and the emergent superconductivity was revealed to have a metastable nature. The discovered robust metastable superconductivity suggests that 2D material is a new platform to induce, control, and functionalize metastable electronic states that are inaccessible in bulk crystals.

Development of 3-D Ice Accretion Measurement Method

NASA Technical Reports Server (NTRS)

Lee, Sam; Broeren, Andy P.; Addy, Harold E., Jr.; Sills, Robert; Pifer, Ellen M.

2012-01-01

A research plan is currently being implemented by NASA to develop and validate the use of a commercial laser scanner to record and archive fully three-dimensional (3-D) ice shapes from an icing wind tunnel. The plan focused specifically upon measuring ice accreted in the NASA Icing Research Tunnel (IRT). The plan was divided into two phases. The first phase was the identification and selection of the laser scanning system and the post-processing software to purchase and develop further. The second phase was the implementation and validation of the selected system through a series of icing and aerodynamic tests. Phase I of the research plan has been completed. It consisted of evaluating several scanning hardware and software systems against an established selection criteria through demonstrations in the IRT. The results of Phase I showed that all of the scanning systems that were evaluated were equally capable of scanning ice shapes. The factors that differentiated the scanners were ease of use and the ability to operate in a wide range of IRT environmental conditions.

Evaluating the validity of the Work Role Functioning Questionnaire (Canadian French version) using classical test theory and item response theory.

PubMed

Hong, Quan Nha; Coutu, Marie-France; Berbiche, Djamal

2017-01-01

The Work Role Functioning Questionnaire (WRFQ) was developed to assess workers' perceived ability to perform job demands and is used to monitor presenteeism. Still few studies on its validity can be found in the literature. The purpose of this study was to assess the items and factorial composition of the Canadian French version of the WRFQ (WRFQ-CF). Two measurement approaches were used to test the WRFQ-CF: Classical Test Theory (CTT) and non-parametric Item Response Theory (IRT). A total of 352 completed questionnaires were analyzed. A four-factor and three-factor model models were tested and shown respectively good fit with 14 items (Root Mean Square Error of Approximation (RMSEA) = 0.06, Standardized Root Mean Square Residual (SRMR) = 0.04, Bentler Comparative Fit Index (CFI) = 0.98) and with 17 items (RMSEA = 0.059, SRMR = 0.048, CFI = 0.98). Using IRT, 13 problematic items were identified, of which 9 were common with CTT. This study tested different models with fewer problematic items found in a three-factor model. Using a non-parametric IRT and CTT for item purification gave complementary results. IRT is still scarcely used and can be an interesting alternative method to enhance the quality of a measurement instrument. More studies are needed on the WRFQ-CF to refine its items and factorial composition.

Biases and power for groups comparison on subjective health measurements.

PubMed

Hamel, Jean-François; Hardouin, Jean-Benoit; Le Neel, Tanguy; Kubis, Gildas; Roquelaure, Yves; Sébille, Véronique

2012-01-01

Subjective health measurements are increasingly used in clinical research, particularly for patient groups comparisons. Two main types of analytical strategies can be used for such data: so-called classical test theory (CTT), relying on observed scores and models coming from Item Response Theory (IRT) relying on a response model relating the items responses to a latent parameter, often called latent trait. Whether IRT or CTT would be the most appropriate method to compare two independent groups of patients on a patient reported outcomes measurement remains unknown and was investigated using simulations. For CTT-based analyses, groups comparison was performed using t-test on the scores. For IRT-based analyses, several methods were compared, according to whether the Rasch model was considered with random effects or with fixed effects, and the group effect was included as a covariate or not. Individual latent traits values were estimated using either a deterministic method or by stochastic approaches. Latent traits were then compared with a t-test. Finally, a two-steps method was performed to compare the latent trait distributions, and a Wald test was performed to test the group effect in the Rasch model including group covariates. The only unbiased IRT-based method was the group covariate Wald's test, performed on the random effects Rasch model. This model displayed the highest observed power, which was similar to the power using the score t-test. These results need to be extended to the case frequently encountered in practice where data are missing and possibly informative.

Intrinsic Membrane Properties of Pre-oromotor Neurons in the Intermediate Zone of the Medullary Reticular Formation

PubMed Central

Venugopal, Sharmila; Boulant, Jack A.; Chen, Zhixiong; Travers, Joseph B.

2010-01-01

Neurons in the lower brainstem that control consummatory behavior are widely distributed in the reticular formation (RF) of the pons and medulla. The intrinsic membrane properties of neurons within this distributed system shape complex excitatory and inhibitory inputs from both orosensory and central structures implicated in homeostatic control to produce coordinated oromotor patterns. The current study explored the intrinsic membrane properties of neurons in the intermediate subdivision of the medullary reticular formation (IRt). Neurons in the IRt receive input from the overlying (gustatory) nucleus of the solitary tract and project to the oromotor nuclei. Recent behavioral pharmacology studies as well as computational modeling suggest that inhibition in the IRt plays an important role in the transition from a taste-initiated oromotor pattern of ingestion to one of rejection. The present study explored the impact of hyperpolarization on membrane properties. In response to depolarization, neurons responded with either a tonic discharge, an irregular/burst pattern or were spike-adaptive. A hyperpolarizing pre-pulse modulated the excitability of most (82%) IRt neurons to subsequent depolarization. Instances of both increased (30%) and decreased (52%) excitability were observed. Currents induced by the hyperpolarization included an outward 4-AP sensitive K+ current that suppressed excitability and an inward cation current that increased excitability. These currents are also present in other subpopulations of RF neurons that influence the oromotor nuclei and we discuss how these currents could alter ring characteristics to impact pattern generation. PMID:20338224

An experimental and theoretical study of the ice accretion process during artificial and natural icing conditions

NASA Technical Reports Server (NTRS)

Kirby, Mark S.; Hansman, R. John

1988-01-01

Real-time measurements of ice growth during artificial and natural icing conditions were conducted using an ultrasonic pulse-echo technique. This technique allows ice thickness to be measured with an accuracy of + or - 0.5 mm; in addition, the ultrasonic signal characteristics may be used to detect the presence of liquid on the ice surface and hence discern wet and dry ice growth behavior. Ice growth was measured on the stagnation line of a cylinder exposed to artificial icing conditions in the NASA Lewis Icing Research Tunnel (IRT), and similarly for a cylinder exposed in flight to natural icing conditions. Ice thickness was observed to increase approximately linearly with exposure time during the initial icing period. The ice accretion rate was found to vary with cloud temperature during wet ice growth, and liquid runback from the stagnation region was inferred. A steady-state energy balance model for the icing surface was used to compare heat transfer characteristics for IRT and natural icing conditions. Ultrasonic measurements of wet and dry ice growth observed in the IRT and in flight were compared with icing regimes predicted by a series of heat transfer coefficients. The heat transfer magnitude was generally inferred to be higher for the IRT than for the natural icing conditions encountered in flight. An apparent variation in the heat transfer magnitude was also observed for flights conducted through different natural icing-cloud formations.

Comprehensive CFTR gene analysis of the French cystic fibrosis screened newborn cohort: implications for diagnosis, genetic counseling, and mutation-specific therapy.

PubMed

Audrézet, Marie Pierre; Munck, Anne; Scotet, Virginie; Claustres, Mireille; Roussey, Michel; Delmas, Dominique; Férec, Claude; Desgeorges, Marie

2015-02-01

Newborn screening (NBS) for cystic fibrosis (CF) was implemented throughout France in 2002. It involves a four-tiered procedure: immunoreactive trypsin (IRT)/DNA/IRT/sweat test [corrected] was implemented throughout France in 2002. The aim of this study was to assess the performance of molecular CFTR gene analysis from the French NBS cohort, to evaluate CF incidence, mutation detection rate, and allelic heterogeneity. During the 8-year period, 5,947,148 newborns were screened for cystic fibrosis. The data were collected by the Association Française pour le Dépistage et la Prévention des Handicaps de l'Enfant. The mutations identified were classified into four groups based on their potential for causing disease, and a diagnostic algorithm was proposed. Combining the genetic and sweat test results, 1,160 neonates were diagnosed as having cystic fibrosis. The corresponding incidence, including both the meconium ileus (MI) and false-negative cases, was calculated at 1 in 4,726 live births. The CF30 kit, completed with a comprehensive CFTR gene analysis, provides an excellent detection rate of 99.77% for the mutated alleles, enabling the identification of a complete genotype in 99.55% of affected neonates. With more than 200 different mutations characterized, we confirmed the French allelic heterogeneity. The very good sensitivity, specificity, and positive predictive value obtained suggest that the four-tiered IRT/DNA/IRT/sweat test procedure may provide an effective strategy for newborn screening for cystic fibrosis.

A Study of Large Droplet Ice Accretions in the NASA-Lewis IRT at Near-Freezing Conditions

NASA Technical Reports Server (NTRS)

Miller, Dean R.; Addy, Harold E. , Jr.; Ide, Robert F.

1996-01-01

This report documents the results of an experimental study on large droplet ice accretions which was conducted in the NASA-Lewis Icing Research Tunnel (IRT) with a full-scale 77.25 inch chord Twin-Otter wing section. This study was intended to: (1) document the existing capability of the IRT to produce a large droplet icing cloud, and (2) study the effect of various parameters on large droplet ice accretions. Results are presented from a study of the IRT's capability to produce large droplets with MVD of 99 and 160 microns. The effect of the initial water droplet temperature on the resultant ice accretion was studied for different initial spray bar air and water temperatures. The initial spray bar water temperature was found to have no discernible effect upon the large droplet ice accretions. Also, analytical and experimental results suggest that the water droplet temperature is very nearly the same as the tunnel ambient temperature, thus providing a realistic simulation of the large droplet natural icing condition. The effect of temperature, droplet size, airspeed, angle-of attack, flap setting and de-icer boot cycling time on ice accretion was studied, and will be discussed in this report. It was found that, in almost all of the cases studied, an ice ridge formed immediately aft of the active portion of the de-icer boot. This ridge was irregular in shape, varied in location, and was in some cases discontinuous due to aerodynamic shedding.

Convective heat transfer measurements from a NACA 0012 airfoil in flight and in the NASA Lewis Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Poinsatte, Philip E.; Vanfossen, G. James; Dewitt, Kenneth J.

1989-01-01

Local heat transfer coefficients were measured on a smooth and roughened NACA 0012 airfoil. Heat transfer measurements on the 0.533 m chord airfoil were made both in flight on the NASA Lewis Twin Otter Icing Research Aircraft and in the NASA Lewis Icing Research Tunnel (IRT). Roughness was obtained by the attachment of uniform 2 mm diameter hemispheres to the airfoil surface in 4 distinct patterns. Flight data were taken for the smooth and roughened airfoil at various Reynolds numbers based on chord in the range 1.24 to 2.50 x 10(exp 6) and at various angles of attack up to 4 deg. During these flight tests, the free stream velocity turbulence intensity was found to be very low (less than 0.1 percent). Wind tunnel data were acquired in the Reynolds number range 1.20 to 4.25 x 10(exp 6) and at angles of attack from -4 to 8 deg. The turbulence intensity in the IRT was 0.5 to 0.7 percent with the cloud generating sprays off. A direct comparison was made between the results obtained in flight and in the IRT. The higher level of turbulence in the IRT vs. flight had little effect on the heat transfer for the lower Reynolds numbers but caused a moderate increase in heat transfer at the high Reynolds numbers. Roughness generally increased the heat transfer.

Thermographic imaging in sports and exercise medicine: A Delphi study and consensus statement on the measurement of human skin temperature.

PubMed

Moreira, Danilo Gomes; Costello, Joseph T; Brito, Ciro J; Adamczyk, Jakub G; Ammer, Kurt; Bach, Aaron J E; Costa, Carlos M A; Eglin, Clare; Fernandes, Alex A; Fernández-Cuevas, Ismael; Ferreira, José J A; Formenti, Damiano; Fournet, Damien; Havenith, George; Howell, Kevin; Jung, Anna; Kenny, Glen P; Kolosovas-Machuca, Eleazar S; Maley, Matthew J; Merla, Arcangelo; Pascoe, David D; Priego Quesada, Jose I; Schwartz, Robert G; Seixas, Adérito R D; Selfe, James; Vainer, Boris G; Sillero-Quintana, Manuel

2017-10-01

The importance of using infrared thermography (IRT) to assess skin temperature (t sk ) is increasing in clinical settings. Recently, its use has been increasing in sports and exercise medicine; however, no consensus guideline exists to address the methods for collecting data in such situations. The aim of this study was to develop a checklist for the collection of t sk using IRT in sports and exercise medicine. We carried out a Delphi study to set a checklist based on consensus agreement from leading experts in the field. Panelists (n = 24) representing the areas of sport science (n = 8; 33%), physiology (n = 7; 29%), physiotherapy (n = 3; 13%) and medicine (n = 6; 25%), from 13 different countries completed the Delphi process. An initial list of 16 points was proposed which was rated and commented on by panelists in three rounds of anonymous surveys following a standard Delphi procedure. The panel reached consensus on 15 items which encompassed the participants' demographic information, camera/room or environment setup and recording/analysis of t sk using IRT. The results of the Delphi produced the checklist entitled "Thermographic Imaging in Sports and Exercise Medicine (TISEM)" which is a proposal to standardize the collection and analysis of t sk data using IRT. It is intended that the TISEM can also be applied to evaluate bias in thermographic studies and to guide practitioners in the use of this technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of indirect ring tension test for fracture characterization of asphalt mixtures

NASA Astrophysics Data System (ADS)

Zeinali Siavashani, Alireza

Low temperature cracking is a major distress in asphalt pavements. Several test configurations have been introduced to characterize the fracture properties of hot mix (HMA); however, most are considered to be research tools due to the complexity of the test methods or equipment. This dissertation describes the development of the indirect ring tension (IRT) fracture test for HMA, which was designed to be an effective and user-friendly test that could be deployed at the Department of Transportation level. The primary advantages of this innovative and yet practical test include: relatively large fracture surface test zone, simplicity of the specimen geometry, widespread availability of the required test equipment, and ability to test laboratory compacted specimens as well as field cores. Numerical modeling was utilized to calibrate the stress intensity factor formula of the IRT fracture test for various specimen dimensions. The results of this extensive analysis were encapsulated in a single equation. To develop the test procedure, a laboratory study was conducted to determine the optimal test parameters for HMA material. An experimental plan was then developed to evaluate the capability of the test in capturing the variations in the mix properties, asphalt pavement density, asphalt material aging, and test temperature. Five plant-produced HMA mixtures were used in this extensive study, and the results revealed that the IRT fracture test is highly repeatable, and capable of capturing the variations in the fracture properties of HMA. Furthermore, an analytical model was developed based on the viscoelastic properties of HMA to estimate the maximum allowable crack size for the pavements in the experimental study. This analysis indicated that the low-temperature cracking potential of the asphalt mixtures is highly sensitive to the fracture toughness and brittleness of the HMA material. Additionally, the IRT fracture test data seemed to correlate well with the data from the distress survey which was conducted on the pavements after five years of service. The maximum allowable crack size analysis revealed that a significant improvement could be realized in terms of the pavements performance if the HMA were to be compacted to a higher density. Finally, the IRT fracture test data were compared to the results of the disk-shaped compact [DC(t)] test. The results of the two tests showed a strong correlation; however, the IRT test seemed to be more repeatable. KEYWORDS: Asphalt Pavement, Low-Temperature Cracking, Fracture Mechanics, Material Characterization, Laboratory Testing.

Aero-Thermal Calibration of the NASA Glenn Icing Research Tunnel (2004 and 2005 Tests)

NASA Technical Reports Server (NTRS)

Arrington, E. Allen; Pastor, Christine M.; Gonsalez, Jose C.; Curry, Monroe R., III

2010-01-01

A full aero-thermal calibration of the NASA Glenn Icing Research Tunnel was completed in 2004 following the replacement of the inlet guide vanes upstream of the tunnel drive system and improvement to the facility total temperature instrumentation. This calibration test provided data used to fully document the aero-thermal flow quality in the IRT test section and to construct calibration curves for the operation of the IRT. The 2004 test was also the first to use the 2-D RTD array, an improved total temperature calibration measurement platform.

Epidemiological Survey of Amoxicillin-Clavulanate Resistance and Corresponding Molecular Mechanisms in Escherichia coli Isolates in France: New Genetic Features of blaTEM Genes

PubMed Central

Leflon-Guibout, V.; Speldooren, V.; Heym, B.; Nicolas-Chanoine, M.-H.

2000-01-01

Amoxicillin-clavulanate resistance (MIC >16 μg/ml) and the corresponding molecular mechanisms were prospectively studied in Escherichia coli over a 3-year period (1996 to 1998) in 14 French hospitals. The overall frequency of resistant E. coli isolates remained stable at about 5% over this period. The highest frequency of resistant isolates (10 to 15%) was observed, independently of the year, among E. coli isolated from lower respiratory tract samples, and the isolation rate of resistant strains was significantly higher in surgical wards than in medical wards in 1998 (7.8 versus 2.8%). The two most frequent mechanisms of resistance for the 3 years were the hyperproduction of the chromosomal class C β-lactamase (48, 38.4, and 39.7%) and the production of inhibitor-resistant TEM (IRT) enzymes (30.4, 37.2, and 41.2%). By using the single-strand conformational polymorphism–PCR technique and sequencing methods, we determined that 59 IRT enzymes corresponded to previously described IRT enzymes whereas 8 were new. Three of these new enzymes derived from TEM-1 by only one amino acid substitution (Ser130Gly, Arg244Gly, and Asn276Asp), whereas three others derived by two amino acid substitutions (Met69Leu and Arg244Ser, Met69Leu and Ile127Val, and Met69Val and Arg275Gln). The two remaining new IRTs showed three amino acid substitutions (Met69Val, Trp165Arg, and Asn276Asp and Met69Ile, Trp165Cys, and Arg275Gln). New genetic features were also found in blaTEM genes, namely, blaTEM-1B with either the promoters Pa and Pb, P4, or a promoter displaying a C→G transversion at position 3 of the −35 consensus sequence and new blaTEM genes, notably one encoding TEM-1 but possessing the silent mutations originally described in blaTEM-2 and then in some blaTEM-encoding IRT enzymes. PMID:10991849

A dimensional approach to understanding severity estimates and risk correlates of marijuana abuse and dependence in adults

PubMed Central

WU, LI-TZY; WOODY, GEORGE E.; YANG, CHONGMING; PAN, JENG-JONG; REEVE, BRYCE B.; BLAZER, DAN G.

2012-01-01

While item response theory (IRT) research shows a latent severity trait underlying response patterns of substance abuse and dependence symptoms, little is known about IRT-based severity estimates in relation to clinically relevant measures. In response to increased prevalences of marijuana-related treatment admissions, an elevated level of marijuana potency, and the debate on medical marijuana use, we applied dimensional approaches to understand IRT-based severity estimates for marijuana use disorders (MUDs) and their correlates while simultaneously considering gender- and race/ethnicity-related differential item functioning (DIF). Using adult data from the 2008 National Survey on Drug Use and Health (N=37,897), DSM-IV criteria for MUDs among past-year marijuana users were examined by IRT, logistic regression, and multiple indicators–multiple causes (MIMIC) approaches. Among 6,917 marijuana users, 15% met criteria for a MUD; another 24% exhibited subthreshold dependence. Abuse criteria were highly correlated with dependence criteria (correlation=0.90), indicating unidimensionality; item information curves revealed redundancy in multiple criteria. MIMIC analyses showed that MUD criteria were positively associated with weekly marijuana use, early marijuana use, other substance use disorders, substance abuse treatment, and serious psychological distress. African Americans and Hispanics showed higher levels of MUDs than whites, even after adjusting for race/ethnicity-related DIF. The redundancy in multiple criteria suggests an opportunity to improve efficiency in measuring symptom-level manifestations by removing low-informative criteria. Elevated rates of MUDs among African Americans and Hispanics require research to elucidate risk factors and improve assessments of MUDs for different racial/ethnic groups. PMID:22351489

Biases and Power for Groups Comparison on Subjective Health Measurements

PubMed Central

Hamel, Jean-François; Hardouin, Jean-Benoit; Le Neel, Tanguy; Kubis, Gildas; Roquelaure, Yves; Sébille, Véronique

2012-01-01

Subjective health measurements are increasingly used in clinical research, particularly for patient groups comparisons. Two main types of analytical strategies can be used for such data: so-called classical test theory (CTT), relying on observed scores and models coming from Item Response Theory (IRT) relying on a response model relating the items responses to a latent parameter, often called latent trait. Whether IRT or CTT would be the most appropriate method to compare two independent groups of patients on a patient reported outcomes measurement remains unknown and was investigated using simulations. For CTT-based analyses, groups comparison was performed using t-test on the scores. For IRT-based analyses, several methods were compared, according to whether the Rasch model was considered with random effects or with fixed effects, and the group effect was included as a covariate or not. Individual latent traits values were estimated using either a deterministic method or by stochastic approaches. Latent traits were then compared with a t-test. Finally, a two-steps method was performed to compare the latent trait distributions, and a Wald test was performed to test the group effect in the Rasch model including group covariates. The only unbiased IRT-based method was the group covariate Wald’s test, performed on the random effects Rasch model. This model displayed the highest observed power, which was similar to the power using the score t-test. These results need to be extended to the case frequently encountered in practice where data are missing and possibly informative. PMID:23115620

Lawton IADL scale in dementia: can item response theory make it more informative?

PubMed

McGrory, Sarah; Shenkin, Susan D; Austin, Elizabeth J; Starr, John M

2014-07-01

impairment of functional abilities represents a crucial component of dementia diagnosis. Current functional measures rely on the traditional aggregate method of summing raw scores. While this summary score provides a quick representation of a person's ability, it disregards useful information on the item level. to use item response theory (IRT) methods to increase the interpretive power of the Lawton Instrumental Activities of Daily Living (IADL) scale by establishing a hierarchy of item 'difficulty' and 'discrimination'. this cross-sectional study applied IRT methods to the analysis of IADL outcomes. Participants were 202 members of the Scottish Dementia Research Interest Register (mean age = 76.39, range = 56-93, SD = 7.89 years) with complete itemised data available. a Mokken scale with good reliability (Molenaar Sijtsama statistic 0.79) was obtained, satisfying the IRT assumption that the items comprise a single unidimensional scale. The eight items in the scale could be placed on a hierarchy of 'difficulty' (H coefficient = 0.55), with 'Shopping' being the most 'difficult' item and 'Telephone use' being the least 'difficult' item. 'Shopping' was the most discriminatory item differentiating well between patients of different levels of ability. IRT methods are capable of providing more information about functional impairment than a summed score. 'Shopping' and 'Telephone use' were identified as items that reveal key information about a patient's level of ability, and could be useful screening questions for clinicians. © The Author 2013. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@ oup.com.

Improving Measurement Efficiency of the Inner EAR Scale with Item Response Theory.

PubMed

Jessen, Annika; Ho, Andrew D; Corrales, C Eduardo; Yueh, Bevan; Shin, Jennifer J

2018-02-01

Objectives (1) To assess the 11-item Inner Effectiveness of Auditory Rehabilitation (Inner EAR) instrument with item response theory (IRT). (2) To determine whether the underlying latent ability could also be accurately represented by a subset of the items for use in high-volume clinical scenarios. (3) To determine whether the Inner EAR instrument correlates with pure tone thresholds and word recognition scores. Design IRT evaluation of prospective cohort data. Setting Tertiary care academic ambulatory otolaryngology clinic. Subjects and Methods Modern psychometric methods, including factor analysis and IRT, were used to assess unidimensionality and item properties. Regression methods were used to assess prediction of word recognition and pure tone audiometry scores. Results The Inner EAR scale is unidimensional, and items varied in their location and information. Information parameter estimates ranged from 1.63 to 4.52, with higher values indicating more useful items. The IRT model provided a basis for identifying 2 sets of items with relatively lower information parameters. Item information functions demonstrated which items added insubstantial value over and above other items and were removed in stages, creating a 8- and 3-item Inner EAR scale for more efficient assessment. The 8-item version accurately reflected the underlying construct. All versions correlated moderately with word recognition scores and pure tone averages. Conclusion The 11-, 8-, and 3-item versions of the Inner EAR scale have strong psychometric properties, and there is correlational validity evidence for the observed scores. Modern psychometric methods can help streamline care delivery by maximizing relevant information per item administered.

A Non-Parametric Item Response Theory Evaluation of the CAGE Instrument Among Older Adults.

PubMed

Abdin, Edimansyah; Sagayadevan, Vathsala; Vaingankar, Janhavi Ajit; Picco, Louisa; Chong, Siow Ann; Subramaniam, Mythily

2018-02-23

The validity of the CAGE using item response theory (IRT) has not yet been examined in older adult population. This study aims to investigate the psychometric properties of the CAGE using both non-parametric and parametric IRT models, assess whether there is any differential item functioning (DIF) by age, gender and ethnicity and examine the measurement precision at the cut-off scores. We used data from the Well-being of the Singapore Elderly study to conduct Mokken scaling analysis (MSA), dichotomous Rasch and 2-parameter logistic IRT models. The measurement precision at the cut-off scores were evaluated using classification accuracy (CA) and classification consistency (CC). The MSA showed the overall scalability H index was 0.459, indicating a medium performing instrument. All items were found to be homogenous, measuring the same construct and able to discriminate well between respondents with high levels of the construct and the ones with lower levels. The item discrimination ranged from 1.07 to 6.73 while the item difficulty ranged from 0.33 to 2.80. Significant DIF was found for 2-item across ethnic group. More than 90% (CC and CA ranged from 92.5% to 94.3%) of the respondents were consistently and accurately classified by the CAGE cut-off scores of 2 and 3. The current study provides new evidence on the validity of the CAGE from the IRT perspective. This study provides valuable information of each item in the assessment of the overall severity of alcohol problem and the precision of the cut-off scores in older adult population.

A review on the application of medical infrared thermal imaging in hands

NASA Astrophysics Data System (ADS)

Sousa, Elsa; Vardasca, Ricardo; Teixeira, Sérgio; Seixas, Adérito; Mendes, Joaquim; Costa-Ferreira, António

2017-09-01

Infrared Thermal (IRT) imaging is a medical imaging modality to study skin temperature in real time, providing physiological information about the underlining structures. One of the most accessible body sites to be investigated using such imaging method is the hands, which can reflect valuable information about conditions affecting the upper limbs. The aim of this review is to acquaint the successful applications of IRT in the hands with a medical scope, opening horizons for future applications based in the achieved results. A systematic literature review was performed in order to assess in which applications medical IRT imaging was applied to the hands. The literature search was conducted in the reference databases: PubMed, Scopus and ISI Web of Science, making use of keywords (hand, thermography, infrared imaging, thermal imaging) combination that were present at the title and abstract. No temporal restriction was made. As a result, 4260 articles were identified, after removal of duplicates, 3224 articles remained and from first title and abstract filtering, a total of 388 articles were considered. After application of exclusion criteria (non-availability, non-clinical applications, reviews, case studies, written in other languages than English and using liquid crystal thermography), 146 articles were considered for this review. It can be verified that thermography provides useful diagnostic and monitoring information of conditions that directly or indirectly related to hands, as well as aiding in the treatment assessment. Trends and future challenges for IRT applications on hands are provided to stimulate researchers and clinicians to explore and address them.

An integrated study for mapping the moisture distribution in an ancient damaged wall painting.

PubMed

Capitani, Donatella; Proietti, Noemi; Gobbino, Marco; Soroldoni, Luigi; Casellato, Umberto; Valentini, Massimo; Rosina, Elisabetta

2009-12-01

An integrated study of microclimate monitoring, IR thermography (IRT), gravimetric tests and portable unilateral nuclear magnetic resonance (NMR) was applied in the framework of planning emergency intervention on a very deteriorated wall painting in San Rocco church, Cornaredo (Milan, Italy). The IRT investigation supported by gravimetric tests showed that the worst damage, due to water infiltration, was localized on the wall painting of the northern wall. Unilateral NMR, a new non-destructive technique which measures the hydrogen signal of the moisture and that was applied directly to the wall, allowed a detailed map of the distribution of the moisture in the plaster underlying the wall panting to be obtained. With a proper calibration of the integral of the recorded signal with suitable specimens, each area of the map corresponded to an accurate amount of moisture. IRT, gravimetric tests and unilateral NMR applied to investigate the northern wall painting showed the presence of two wet areas separated by a dry area. The moisture found in the lower area was ascribed to the occurrence of rising damp at the bottom of the wall due to the slope of the garden soil towards the northern exterior. The moisture found in the upper area was ascribed to condensation phenomena associated with the presence of a considerable amount of soluble, hygroscopic salts. In the framework of this integrated study, IRT investigation and gravimetric methods validated portable unilateral NMR as a new analytical tool for measuring in situ and without any sampling of the distribution and amount of moisture in wall paintings.

Intrinsic membrane properties of pre-oromotor neurons in the intermediate zone of the medullary reticular formation.

PubMed

Venugopal, S; Boulant, J A; Chen, Z; Travers, J B

2010-06-16

Neurons in the lower brainstem that control consummatory behavior are widely distributed in the reticular formation (RF) of the pons and medulla. The intrinsic membrane properties of neurons within this distributed system shape complex excitatory and inhibitory inputs from both orosensory and central structures implicated in homeostatic control to produce coordinated oromotor patterns. The current study explored the intrinsic membrane properties of neurons in the intermediate subdivision of the medullary reticular formation (IRt). Neurons in the IRt receive input from the overlying (gustatory) nucleus of the solitary tract and project to the oromotor nuclei. Recent behavioral pharmacology studies as well as computational modeling suggest that inhibition in the IRt plays an important role in the transition from a taste-initiated oromotor pattern of ingestion to one of rejection. The present study explored the impact of hyperpolarization on membrane properties. In response to depolarization, neurons responded with either a tonic discharge, an irregular/burst pattern or were spike-adaptive. A hyperpolarizing pre-pulse modulated the excitability of most (82%) IRt neurons to subsequent depolarization. Instances of both increased (30%) and decreased (52%) excitability were observed. Currents induced by the hyperpolarization included an outward 4-aminopyridine (4-AP) sensitive K+ current that suppressed excitability and an inward cation current that increased excitability. These currents are also present in other subpopulations of RF neurons that influence the oromotor nuclei and we discuss how these currents could alter firing characteristics to impact pattern generation. 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

Item response theory analysis of the Pain Self-Efficacy Questionnaire.

PubMed

Costa, Daniel S J; Asghari, Ali; Nicholas, Michael K

2017-01-01

The Pain Self-Efficacy Questionnaire (PSEQ) is a 10-item instrument designed to assess the extent to which a person in pain believes s/he is able to accomplish various activities despite their pain. There is strong evidence for the validity and reliability of both the full-length PSEQ and a 2-item version. The purpose of this study is to further examine the properties of the PSEQ using an item response theory (IRT) approach. We used the two-parameter graded response model to examine the category probability curves, and location and discrimination parameters of the 10 PSEQ items. In item response theory, responses to a set of items are assumed to be probabilistically determined by a latent (unobserved) variable. In the graded-response model specifically, item response threshold (the value of the latent variable for which adjacent response categories are equally likely) and discrimination parameters are estimated for each item. Participants were 1511 mixed, chronic pain patients attending for initial assessment at a tertiary pain management centre. All items except item 7 ('I can cope with my pain without medication') performed well in IRT analysis, and the category probability curves suggested that participants used the 7-point response scale consistently. Items 6 ('I can still do many of the things I enjoy doing, such as hobbies or leisure activity, despite pain'), 8 ('I can still accomplish most of my goals in life, despite the pain') and 9 ('I can live a normal lifestyle, despite the pain') captured higher levels of the latent variable with greater precision. The results from this IRT analysis add to the body of evidence based on classical test theory illustrating the strong psychometric properties of the PSEQ. Despite the relatively poor performance of Item 7, its clinical utility warrants its retention in the questionnaire. The strong psychometric properties of the PSEQ support its use as an effective tool for assessing self-efficacy in people with pain. Copyright © 2016 Scandinavian Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

A New Look at the Psychometrics of the Parenting Scale through the Lens of Item Response Theory

PubMed Central

Lorber, Michael F.; Xu, Shu; Smith Slep, Amy M.; Bulling, Lisanne; O'Leary, Susan G.

2015-01-01

The psychometrics of the Parenting Scale's Overreactivity and Laxness subscales were evaluated using item response theory (IRT) techniques. The IRT analyses were based on two community samples of cohabiting parents of 3- to 8-year-old children, combined to yield an N of 852 families. The results supported the utility of the Overreactivity and Laxness subscales, particularly in discriminating among parents in the mid to upper reaches of each construct. The original versions of the Overreactivity and Laxness subscales were more reliable than alternative, shorter versions identified in replicated factor analyses from previously published research and in IRT analyses in the present research. Moreover, in several cases, the original versions of these subscales, in comparison with the shortened versions, exhibited greater six-month stabilities and correlations with child externalizing behavior and couple relationship satisfaction. Reliability was greater for the Laxness than for the Overreactivity subscale. Item performance on each subscale was highly variable. Together, the present findings are generally supportive of the psychometrics of the Parenting Scale, particularly for clinical research and practice. They also suggest areas for further development. PMID:24828855

A new look at the psychometrics of the parenting scale through the lens of item response theory.

PubMed

Lorber, Michael F; Xu, Shu; Slep, Amy M Smith; Bulling, Lisanne; O'Leary, Susan G

2014-01-01

The psychometrics of the Parenting Scale's Overreactivity and Laxness subscales were evaluated using item response theory (IRT) techniques. The IRT analyses were based on 2 community samples of cohabiting parents of 3- to 8-year-old children, combined to yield a total sample size of 852 families. The results supported the utility of the Overreactivity and Laxness subscales, particularly in discriminating among parents in the mid to upper reaches of each construct. The original versions of the Overreactivity and Laxness subscales were more reliable than alternative, shorter versions identified in replicated factor analyses from previously published research and in IRT analyses in the present research. Moreover, in several cases, the original versions of these subscales, in comparison with the shortened versions, exhibited greater 6-month stabilities and correlations with child externalizing behavior and couple relationship satisfaction. Reliability was greater for the Laxness than for the Overreactivity subscale. Item performance on each subscale was highly variable. Together, the present findings are generally supportive of the psychometrics of the Parenting Scale, particularly for clinical research and practice. They also suggest areas for further development.

Coma Recovery Scale-Revised: evidentiary support for hierarchical grading of level of consciousness.

PubMed

Gerrard, Paul; Zafonte, Ross; Giacino, Joseph T

2014-12-01

To investigate the neurobehavioral pattern of recovery of consciousness as reflected by performance on the subscales of the Coma Recovery Scale-Revised (CRS-R). Retrospective item response theory (IRT) and factor analysis. Inpatient rehabilitation facilities. Rehabilitation inpatients (N=180) with posttraumatic disturbance in consciousness who participated in a double-blinded, randomized, controlled drug trial. Not applicable. Scores on CRS-R subscales. The CRS-R was found to fit factor analytic models adhering to the assumptions of unidimensionality and monotonicity. In addition, subscales were mutually independent based on residual correlations. Nonparametric IRT reaffirmed the finding of monotonicity. A highly constrained confirmatory factor analysis model, which imposed equal factor loadings on all items, was found to fit the data well and was used to estimate a 1-parameter IRT model. This study provides evidence of the unidimensionality of the CRS-R and supports the hierarchical structure of the CRS-R subscales, suggesting that it is an effective tool for establishing diagnosis and monitoring recovery of consciousness after severe traumatic brain injury. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Building of scientific information system for sustainable development of BNCT in Bulgaria.

PubMed

Mitev, M; Ilieva, K; Apostolov, T

2009-07-01

Building a boron neutron capture therapy (BNCT) facility is foreseen within the reconstruction of the Research Reactor IRT (IRT) of the Institute for Nuclear Research and Nuclear Energy of the Bulgaria Academy of Sciences (INRNE). The development of BNCT at IRT plays a very significant role in the plan for sustainable application of the reactor. A centralized scientific information system on BNCT is being built at the INRNE with the purpose to collect and sort new information as knowledge accumulated during more than thirty years history of BNCT. This BNCT information system will help the creation and consolidation of a well informed and interconnected interdisciplinary team of physicists, chemists, biologists, and radio-oncologists for establishing BNCT cancer treatment in Bulgaria. It will strengthen more intensive development of the national network as well as its enlargement to the Balkan region countries. Furthermore, to acquaint the public at large with the opportunity for BNCT cancer treatment will be addressed. Human, social, and economics results due to BNCT for many patients from Balkan region are expected.

Sensitive observations with the Spacelab 2 infrared telescope

NASA Technical Reports Server (NTRS)

Young, E. T.; Rieke, G. H.; Gautier, T. N.; Hoffmann, W. F.; Low, F. J.; Poteet, W.; Fazio, G. G.; Koch, D.; Traub, W. A.; Urban, E. W.

1983-01-01

The small helium-cooled infrared telescope (Spacelab IRT) is a multiband instrument capable of highly sensitive observations from space. The experiment consists of a cryogenically cooled, very well baffled telescope with a ten channel focal plane array. During the Spacelab 2 flight of the Space Shuttle, this instrument will make observations between 5 and 120 micron wavelength that will be background limited by the expected zodiacal emission. Design considerations necessitated by this level of performance are discussed in this paper. In particular, the operation of a very sensitive focal plane array in the space environment is described. The Spacelab IRT will be used to map the extended, low-surface brightness celestial emission. During the seven day length of the mission better than 70 percent sky coverage is expected. The instrument will also be used to measure the infrared contamination environment of the Space Shuttle. This information will be important in the development of the next generation of infrared astronomical instruments. The performance of the Spacelab IRT, in particular its sensitivity to the contamination environment is detailed.

The application of item response theory in developing and validating a shortened version of the Emirate Marital Satisfaction Scale.

PubMed

Dodeen, Hamzeh; Al-Darmaki, Fatima

2016-12-01

The aim of this study was to determine the feasibility of generating a shorter version of the Emirati Marital Satisfaction Scale (EMSS) using item response theory (IRT)-based methodology. The EMSS is the first national scale used to provide an understanding of the family function and level of marital satisfaction within the cultural context of the United Arab Emirates. A sample of 1,049 Emirati married individuals from different ages, genders, places of residence, and monthly incomes participated in this study. The IRT was calibrated using X-Calibre 4.2 and the graded response model. The analysis was developed on the basis of a short form of the EMSS (7 items), which constitutes a promising alternative to the original scale for practitioners and researchers. This short version is reliable, valid, and it gives results very similar to the original scale. The results of this study confirmed the usefulness of IRT-based methodology for developing psychological and counseling scales. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Implementation of newborn screening for cystic fibrosis in Norway. Results from the first three years.

PubMed

Lundman, Emma; Gaup, H Junita; Bakkeheim, Egil; Olafsdottir, Edda J; Rootwelt, Terje; Storrøsten, Olav Trond; Pettersen, Rolf D

2016-05-01

Norway introduced newborn screening for cystic fibrosis (CF) March 1, 2012. We present results from the first three years of the national newborn CF screening program. Positive primary screening of immunoreactive trypsinogen (IRT) was followed by DNA testing of the Cystic fibrosis transmembrane conductance regulator (CFTR) gene. Infants with two CFTR mutations were reported for diagnostic follow-up. Of 181,859 infants tested, 1454 samples (0.80%) were assessed for CFTR mutations. Forty children (1:4546) had two CFTR mutations, of which only 21 (1:8660) were confirmed to have a CF diagnosis. The CFTR mutations differed from previously clinically diagnosed CF patients, and p.R117H outnumbered p.F508del as the most frequent mutation. One child with a negative IRT screening test was later clinically diagnosed with CF. The CF screening program identified fewer children with a conclusive CF diagnosis than expected. Our data suggest a revision of the IRT/DNA protocol. Copyright © 2016 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.

An Orchestrated Intron Retention Program in Meiosis Controls Timely Usage of Transcripts during Germ Cell Differentiation.

PubMed

Naro, Chiara; Jolly, Ariane; Di Persio, Sara; Bielli, Pamela; Setterblad, Niclas; Alberdi, Antonio J; Vicini, Elena; Geremia, Raffaele; De la Grange, Pierre; Sette, Claudio

2017-04-10

Global transcriptome reprogramming during spermatogenesis ensures timely expression of factors in each phase of male germ cell differentiation. Spermatocytes and spermatids require particularly extensive reprogramming of gene expression to switch from mitosis to meiosis and to support gamete morphogenesis. Here, we uncovered an extensive alternative splicing program during this transmeiotic differentiation. Notably, intron retention was largely the most enriched pattern, with spermatocytes showing generally higher levels of retention compared with spermatids. Retained introns are characterized by weak splice sites and are enriched in genes with strong relevance for gamete function. Meiotic intron-retaining transcripts (IRTs) were exclusively localized in the nucleus. However, differently from other developmentally regulated IRTs, they are stable RNAs, showing longer half-life than properly spliced transcripts. Strikingly, fate-mapping experiments revealed that IRTs are recruited onto polyribosomes days after synthesis. These studies reveal an unexpected function for regulated intron retention in modulation of the timely expression of select transcripts during spermatogenesis. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Assessing the equivalence of Web-based and paper-and-pencil questionnaires using differential item and test functioning (DIF and DTF) analysis: a case of the Four-Dimensional Symptom Questionnaire (4DSQ).

PubMed

Terluin, Berend; Brouwers, Evelien P M; Marchand, Miquelle A G; de Vet, Henrica C W

2018-05-01

Many paper-and-pencil (P&P) questionnaires have been migrated to electronic platforms. Differential item and test functioning (DIF and DTF) analysis constitutes a superior research design to assess measurement equivalence across modes of administration. The purpose of this study was to demonstrate an item response theory (IRT)-based DIF and DTF analysis to assess the measurement equivalence of a Web-based version and the original P&P format of the Four-Dimensional Symptom Questionnaire (4DSQ), measuring distress, depression, anxiety, and somatization. The P&P group (n = 2031) and the Web group (n = 958) consisted of primary care psychology clients. Unidimensionality and local independence of the 4DSQ scales were examined using IRT and Yen's Q3. Bifactor modeling was used to assess the scales' essential unidimensionality. Measurement equivalence was assessed using IRT-based DIF analysis using a 3-stage approach: linking on the latent mean and variance, selection of anchor items, and DIF testing using the Wald test. DTF was evaluated by comparing expected scale scores as a function of the latent trait. The 4DSQ scales proved to be essentially unidimensional in both modalities. Five items, belonging to the distress and somatization scales, displayed small amounts of DIF. DTF analysis revealed that the impact of DIF on the scale level was negligible. IRT-based DIF and DTF analysis is demonstrated as a way to assess the equivalence of Web-based and P&P questionnaire modalities. Data obtained with the Web-based 4DSQ are equivalent to data obtained with the P&P version.

A new Integrated Negative Symptom structure of the Positive and Negative Syndrome Scale (PANSS) in schizophrenia using item response analysis.

PubMed

Khan, Anzalee; Lindenmayer, Jean-Pierre; Opler, Mark; Yavorsky, Christian; Rothman, Brian; Lucic, Luka

2013-10-01

Debate persists with regard to how best to categorize the syndromal dimension of negative symptoms in schizophrenia. The aim was to first review published Principle Components Analysis (PCA) of the PANSS, and extract items most frequently included in the negative domain, and secondly, to examine the quality of items using Item Response Theory (IRT) to select items that best represent a measurable dimension (or dimensions) of negative symptoms. First, 22 factor analyses and PCA met were included. Second, using a large dataset (n=7187) of participants in clinical trials with chronic schizophrenia, we extracted items loading on one or more PCA. Third, items not loading with a value of ≥ 0.5, or loading on more than one component with values of ≥ 0.5 were discarded. Fourth, resulting items were included in a non-parametric IRT and retained based on Option Characteristic Curves (OCCs) and Item Characteristic Curves (ICCs). 15 items loaded on a negative domain in at least one study, with Emotional Withdrawal loading on all studies. Non-parametric IRT retained nine items as an Integrated Negative Factor: Emotional Withdrawal, Blunted Affect, Passive/Apathetic Social Withdrawal, Poor Rapport, Lack of Spontaneity/Conversation Flow, Active Social Avoidance, Disturbance of Volition, Stereotyped Thinking and Difficulty in Abstract Thinking. This is the first study to use a psychometric IRT process to arrive at a set of negative symptom items. Future steps will include further examination of these nine items in terms of their stability, sensitivity to change, and correlations with functional and cognitive outcomes. © 2013 Elsevier B.V. All rights reserved.

The Motivational Value Systems Questionnaire (MVSQ): Psychometric Analysis Using a Forced Choice Thurstonian IRT Model

PubMed Central

Merk, Josef; Schlotz, Wolff; Falter, Thomas

2017-01-01

This study presents a new measure of value systems, the Motivational Value Systems Questionnaire (MVSQ), which is based on a theory of value systems by psychologist Clare W. Graves. The purpose of the instrument is to help people identify their personal hierarchies of value systems and thus become more aware of what motivates and demotivates them in work-related contexts. The MVSQ is a forced-choice (FC) measure, making it quicker to complete and more difficult to intentionally distort, but also more difficult to assess its psychometric properties due to ipsativity of FC data compared to rating scales. To overcome limitations of ipsative data, a Thurstonian IRT (TIRT) model was fitted to the questionnaire data, based on a broad sample of N = 1,217 professionals and students. Comparison of normative (IRT) scale scores and ipsative scores suggested that MVSQ IRT scores are largely freed from restrictions due to ipsativity and thus allow interindividual comparison of scale scores. Empirical reliability was estimated using a sample-based simulation approach which showed acceptable and good estimates and, on average, slightly higher test-retest reliabilities. Further, validation studies provided evidence on both construct validity and criterion-related validity. Scale score correlations and associations of scores with both age and gender were largely in line with theoretically- and empirically-based expectations, and results of a multitrait-multimethod analysis supports convergent and discriminant construct validity. Criterion validity was assessed by examining the relation of value system preferences to departmental affiliation which revealed significant relations in line with prior hypothesizing. These findings demonstrate the good psychometric properties of the MVSQ and support its application in the assessment of value systems in work-related contexts. PMID:28979228

Using self-reported callous-unemotional traits to cross-nationally assess the DSM-5 'With Limited Prosocial Emotions' specifier.

PubMed

Kimonis, Eva R; Fanti, Kostas A; Frick, Paul J; Moffitt, Terrie E; Essau, Cecilia; Bijttebier, Patricia; Marsee, Monica A

2015-11-01

The presence of callous-unemotional (CU) traits designates an important subgroup of antisocial youth at risk for severe, persistent, and impairing conduct problems. As a result, the fifth revision of the Diagnostic and Statistical Manual includes a specifier for youth meeting diagnostic criteria for Conduct Disorder who show elevated CU traits. The current study evaluated the DSM-5 criteria using Item Response Theory (IRT) analyses and evaluated two methods for using a self-report measure of CU traits to make this diagnosis. The sample included 2257 adolescent (M age = 15.64, SD = 1.69 years) boys (53%) and girls (47%) from community and incarcerated settings in the United States and the European countries of Belgium, Germany, and Cyprus. IRT analyses suggested that four- or eight-item sets from the self-report measure (comparable to the symptoms used by the DSM-5 specifier) provided good model fit, suggesting that they assess a single underlying CU construct. Further, the most stringent method of scoring the self-report scale (i.e. taking only the most extreme responses) to approximate symptom presence provided the best discrimination in IRT analyses, showed reasonable prevalence rates of the specifier, and designated community adolescents who were highly antisocial, whereas the less stringent method best discriminated detained youth. Refined self-report scales developed on the basis of IRT findings provided good assessments of most of the symptoms used in the DSM-5 criteria. These scales may be used as one component of a multimethod assessment of the 'With Limited Prosocial Emotions' specifier for Conduct Disorder. © 2014 Association for Child and Adolescent Mental Health.

The Motivational Value Systems Questionnaire (MVSQ): Psychometric Analysis Using a Forced Choice Thurstonian IRT Model.

PubMed

Merk, Josef; Schlotz, Wolff; Falter, Thomas

2017-01-01

This study presents a new measure of value systems, the Motivational Value Systems Questionnaire (MVSQ), which is based on a theory of value systems by psychologist Clare W. Graves. The purpose of the instrument is to help people identify their personal hierarchies of value systems and thus become more aware of what motivates and demotivates them in work-related contexts. The MVSQ is a forced-choice (FC) measure, making it quicker to complete and more difficult to intentionally distort, but also more difficult to assess its psychometric properties due to ipsativity of FC data compared to rating scales. To overcome limitations of ipsative data, a Thurstonian IRT (TIRT) model was fitted to the questionnaire data, based on a broad sample of N = 1,217 professionals and students. Comparison of normative (IRT) scale scores and ipsative scores suggested that MVSQ IRT scores are largely freed from restrictions due to ipsativity and thus allow interindividual comparison of scale scores. Empirical reliability was estimated using a sample-based simulation approach which showed acceptable and good estimates and, on average, slightly higher test-retest reliabilities. Further, validation studies provided evidence on both construct validity and criterion-related validity. Scale score correlations and associations of scores with both age and gender were largely in line with theoretically- and empirically-based expectations, and results of a multitrait-multimethod analysis supports convergent and discriminant construct validity. Criterion validity was assessed by examining the relation of value system preferences to departmental affiliation which revealed significant relations in line with prior hypothesizing. These findings demonstrate the good psychometric properties of the MVSQ and support its application in the assessment of value systems in work-related contexts.

Clinical vs. Self-report Versions of the Quick Inventory of Depressive Symptomatology in a Public Sector Sample

PubMed Central

Bernstein, Ira H.; Rush, A. John; Carmody, Thomas J.; Woo, Ada; Trivedi, Madhukar H.

2007-01-01

Objectives Recent work using classical test theory (CTT) and item response theory (IRT) has found that the self-report (QIDS-SR16) and clinician-rated (QIDS-C16) versions of the 16-item Quick Inventory of Depressive Symptomatology were generally comparable in outpatients with nonpsychotic major depressive disorder (MDD). This report extends this comparison to a less well-educated, more treatment-resistant sample that included more ethnic/racial minorities using IRT and selected classical test analyses. Methods The QIDS-SR16 and QIDS-C16 were obtained in a sample of 441 outpatients with nonpsychotic MDD seen in the public sector in the Texas Medication Algorithm Project (TMAP). The Samejima graded response IRT model was used to compare the QIDS-SR16 and QIDS-C16. Results The nine symptom domains in the QIDS-SR16 and QIDS-C16 related well to overall depression. The slopes of the item response functions a), which index the strength of relationship between overall depression and each symptom, were extremely similar with the two measures. Likewise, the CTT and IRT indices of symptom frequency (item means and locations of the item response functions, bi) were also similar with these two measures. For example, sad mood and difficulty with concentration/decision making were highly related to the overall depression severity with both the QIDS-C16 and QIDS-SR16. Likewise, sleeping difficulties were commonly reported, even though they were not as strongly related to overall magnitude of depression. Conclusion In this less educated, socially disadvantaged sample, differences between the QIDS-C16 and QIDS-SR16 were minor. The QIDS-SR16 is a satisfactory substitute for the more time-consuming QIDS-C16 in a broad range of adult, nonpsychotic, depressed outpatients. PMID:16716351

Clinical vs. self-report versions of the quick inventory of depressive symptomatology in a public sector sample.

PubMed

Bernstein, Ira H; Rush, A John; Carmody, Thomas J; Woo, Ada; Trivedi, Madhukar H

2007-01-01

Recent work using classical test theory (CTT) and item response theory (IRT) has found that the self-report (QIDS-SR(16)) and clinician-rated (QIDS-C(16)) versions of the 16-item quick inventory of depressive symptomatology were generally comparable in outpatients with nonpsychotic major depressive disorder (MDD). This report extends this comparison to a less well-educated, more treatment-resistant sample that included more ethnic/racial minorities using IRT and selected classical test analyses. The QIDS-SR(16) and QIDS-C(16) were obtained in a sample of 441 outpatients with nonpsychotic MDD seen in the public sector in the Texas Medication Algorithm Project (TMAP). The Samejima graded response IRT model was used to compare the QIDS-SR(16) and QIDS-C(16). The nine symptom domains in the QIDS-SR(16) and QIDS-C(16) related well to overall depression. The slopes of the item response functions, a, which index the strength of relationship between overall depression and each symptom, were extremely similar with the two measures. Likewise, the CTT and IRT indices of symptom frequency (item means and locations of the item response functions, b(i) were also similar with these two measures. For example, sad mood and difficulty with concentration/decision making were highly related to the overall depression severity with both the QIDS-C(16) and QIDS-SR(16). Likewise, sleeping difficulties were commonly reported, even though they were not as strongly related to overall magnitude of depression. In this less educated, socially disadvantaged sample, differences between the QIDS-C(16) and QIDS-SR(16) were minor. The QIDS-SR(16) is a satisfactory substitute for the more time-consuming QIDS-C(16) in a broad range of adult, nonpsychotic, depressed outpatients.

Overview of classical test theory and item response theory for the quantitative assessment of items in developing patient-reported outcomes measures.

PubMed

Cappelleri, Joseph C; Jason Lundy, J; Hays, Ron D

2014-05-01

The US Food and Drug Administration's guidance for industry document on patient-reported outcomes (PRO) defines content validity as "the extent to which the instrument measures the concept of interest" (FDA, 2009, p. 12). According to Strauss and Smith (2009), construct validity "is now generally viewed as a unifying form of validity for psychological measurements, subsuming both content and criterion validity" (p. 7). Hence, both qualitative and quantitative information are essential in evaluating the validity of measures. We review classical test theory and item response theory (IRT) approaches to evaluating PRO measures, including frequency of responses to each category of the items in a multi-item scale, the distribution of scale scores, floor and ceiling effects, the relationship between item response options and the total score, and the extent to which hypothesized "difficulty" (severity) order of items is represented by observed responses. If a researcher has few qualitative data and wants to get preliminary information about the content validity of the instrument, then descriptive assessments using classical test theory should be the first step. As the sample size grows during subsequent stages of instrument development, confidence in the numerical estimates from Rasch and other IRT models (as well as those of classical test theory) would also grow. Classical test theory and IRT can be useful in providing a quantitative assessment of items and scales during the content-validity phase of PRO-measure development. Depending on the particular type of measure and the specific circumstances, the classical test theory and/or the IRT should be considered to help maximize the content validity of PRO measures. Copyright © 2014 Elsevier HS Journals, Inc. All rights reserved.

Using item response theory to address vulnerabilities in FFQ.

PubMed

Kazman, Josh B; Scott, Jonathan M; Deuster, Patricia A

2017-09-01

The limitations for self-reporting of dietary patterns are widely recognised as a major vulnerability of FFQ and the dietary screeners/scales derived from FFQ. Such instruments can yield inconsistent results to produce questionable interpretations. The present article discusses the value of psychometric approaches and standards in addressing these drawbacks for instruments used to estimate dietary habits and nutrient intake. We argue that a FFQ or screener that treats diet as a 'latent construct' can be optimised for both internal consistency and the value of the research results. Latent constructs, a foundation for item response theory (IRT)-based scales (e.g. Patient Reported Outcomes Measurement Information System) are typically introduced in the design stage of an instrument to elicit critical factors that cannot be observed or measured directly. We propose an iterative approach that uses such modelling to refine FFQ and similar instruments. To that end, we illustrate the benefits of psychometric modelling by using items and data from a sample of 12 370 Soldiers who completed the 2012 US Army Global Assessment Tool (GAT). We used factor analysis to build the scale incorporating five out of eleven survey items. An IRT-driven assessment of response category properties indicates likely problems in the ordering or wording of several response categories. Group comparisons, examined with differential item functioning (DIF), provided evidence of scale validity across each Army sub-population (sex, service component and officer status). Such an approach holds promise for future FFQ.

Automatic control study of the icing research tunnel refrigeration system

NASA Technical Reports Server (NTRS)

Kieffer, Arthur W.; Soeder, Ronald H.

1991-01-01

The Icing Research Tunnel (IRT) at the NASA Lewis Research Center is a subsonic, closed-return atmospheric tunnel. The tunnel includes a heat exchanger and a refrigeration plant to achieve the desired air temperature and a spray system to generate the type of icing conditions that would be encountered by aircraft. At the present time, the tunnel air temperature is controlled by manual adjustment of freon refrigerant flow control valves. An upgrade of this facility calls for these control valves to be adjusted by an automatic controller. The digital computer simulation of the IRT refrigeration plant and the automatic controller that was used in the simulation are discussed.

Flow Quality Surveys in the Settling Chamber of the NASA Glenn Icing Research Tunnel (2011 Tests)

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Van Zante, Judith Foss; Broeren, Andy P.; Kubiak, Mark J.

2012-01-01

In 2011, the heat exchanger and refrigeration plant for NASA Glenn Research Center's Icing Research Tunnel (IRT) were upgraded. Flow quality surveys were performed in the settling chamber of the IRT in order to understand the effect that the new heat exchanger had on the flow quality upstream of the spray bars. Measurements were made of the total pressure, static pressure, total temperature, airspeed, and ow angle (pitch and yaw). These measurements were directly compared to measurements taken in 2000, after the previous heat exchanger was installed. In general, the flow quality appears to have improved with the new heat exchanger.

Looking Closer at the Effects of Framing on Risky Choice: An Item Response Theory Analysis.

PubMed

Sickar; Highhouse

1998-07-01

Item response theory (IRT) methodology allowed an in-depth examination of several issues that would be difficult to explore using traditional methodology. IRT models were estimated for 4 risky-choice items, answered by students under either a gain or loss frame. Results supported the typical framing finding of risk-aversion for gains and risk-seeking for losses but also suggested that a latent construct we label preference for risk was influential in predicting risky choice. Also, the Asian Disease item, most often used in framing research, was found to have anomalous statistical properties when compared to other framing items. Copyright 1998 Academic Press.

Flow Quality Surveys in the Settling Chamber of the NASA Glenn Icing Research Tunnel (2011 Tests)

NASA Technical Reports Server (NTRS)

Steen, Laura E.; VanZante, Judith Foss; Broeren, Andy P.; Kubiak, Mark J.

2012-01-01

In 2011, the heat exchanger and refrigeration plant for NASA Glenn Research Center's Icing Research Tunnel (IRT) were upgraded. Flow quality surveys were performed in the settling chamber of the IRT in order to understand the effect that the new heat exchanger had on the flow quality upstream of the spray bars. Measurements were made of the total pressure, static pressure, total temperature, airspeed, and flow angle (pitch and yaw). These measurements were directly compared to measurements taken in 2000, after the previous heat exchanger was installed. In general, the flow quality appears to have improved with the new heat exchanger.

Flow Quality Surveys in the Settling Chamber of the NASA Glenn Icing Research Tunnel (2011 Tests)

NASA Technical Reports Server (NTRS)

Steen, Laura E.; VanZante, Judith Foss; Broeren, Andy P.; Kubiak, Mark J.

2014-01-01

In 2011, the heat exchanger and refrigeration plant for NASA Glenn Research Centers Icing Research Tunnel (IRT) were upgraded. Flow quality surveys were performed in the settling chamber of the IRT in order to understand the effect that the new heat exchanger had on the flow quality upstream of the spray bars. Measurements were made of the total pressure, static pressure, total temperature, airspeed, and flow angle (pitch and yaw). These measurements were directly compared to measurements taken in 2000, after the previous heat exchanger was installed. In general, the flow quality appears to have improved with the new heat exchanger.

Infrared thermography of the pig thorax: an assessment of selected regions of interest by computed tomographical and anatomical parameters.

PubMed

Menzel, A; Siewert, C; Gasse, H; Seifert, H; Hoeltig, D; Hennig-Pauka, I

2015-04-01

Current methods of diagnosis of respiratory diseases in swine are invasive, time-consuming and expensive. Infrared thermography (IRT) of the thorax might provide a new method of high specificity to select swine affected with lung alterations for further diagnostics. In this study, layer thickness of different tissues was determined in frozen thorax slices (FTS) by computed tomography (CT) and then related to skin temperatures measured by IRT in healthy pigs. The aim was to determine appropriate regions of interest (ROI) for evaluation of IRT images. Organ layer thicknesses measured in CT images correspond to those measured in FTS. Temperature differences between lung ROIs and abdomen ROIs were positively correlated with lung layer thickness at certain localizations, and negatively correlated with the thickness of the thorax wall and of inner organ layers. Reference values of differences between skin temperatures were established for two ROIs on the thorax with potential practical use for lung health status determination. Respective ROIs were located on vertical lines crossing the 7th (right) and the 10th (left) thoracic vertebrae. The presence of ribs affected skin temperature significantly. © 2014 Blackwell Verlag GmbH.

Infrared Thermography-based Biophotonics: Integrated Diagnostic Technique for Systemic Reaction Monitoring

NASA Astrophysics Data System (ADS)

Vainer, Boris G.; Morozov, Vitaly V.

A peculiar branch of biophotonics is a measurement, visualisation and quantitative analysis of infrared (IR) radiation emitted from living object surfaces. Focal plane array (FPA)-based IR cameras make it possible to realize in medicine the so called interventional infrared thermal diagnostics. An integrated technique aimed at the advancement of this new approach in biomedical science and practice is described in the paper. The assembled system includes a high-performance short-wave (2.45-3.05 μm) or long-wave (8-14 μm) IR camera, two laser Doppler flowmeters (LDF) and additional equipment and complementary facilities implementing the monitoring of human cardiovascular status. All these means operate synchronously. It is first ascertained the relationship between infrared thermography (IRT) and LDF data in humans in regard to their systemic cardiovascular reactivity. Blood supply real-time dynamics in a narcotized patient is first visualized and quantitatively represented during surgery in order to observe how the general hyperoxia influences thermoregulatory mechanisms; an abrupt increase in temperature of the upper limb is observed using IRT. It is outlined that the IRT-based integrated technique may act as a take-off runway leading to elaboration of informative new methods directly applicable to medicine and biomedical sciences.

An introduction to mixture item response theory models.

PubMed

De Ayala, R J; Santiago, S Y

2017-02-01

Mixture item response theory (IRT) allows one to address situations that involve a mixture of latent subpopulations that are qualitatively different but within which a measurement model based on a continuous latent variable holds. In this modeling framework, one can characterize students by both their location on a continuous latent variable as well as by their latent class membership. For example, in a study of risky youth behavior this approach would make it possible to estimate an individual's propensity to engage in risky youth behavior (i.e., on a continuous scale) and to use these estimates to identify youth who might be at the greatest risk given their class membership. Mixture IRT can be used with binary response data (e.g., true/false, agree/disagree, endorsement/not endorsement, correct/incorrect, presence/absence of a behavior), Likert response scales, partial correct scoring, nominal scales, or rating scales. In the following, we present mixture IRT modeling and two examples of its use. Data needed to reproduce analyses in this article are available as supplemental online materials at http://dx.doi.org/10.1016/j.jsp.2016.01.002. Copyright © 2016 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.

Item response theory analyses of the Delis-Kaplan Executive Function System card sorting subtest.

PubMed

Spencer, Mercedes; Cho, Sun-Joo; Cutting, Laurie E

2018-02-02

In the current study, we examined the dimensionality of the 16-item Card Sorting subtest of the Delis-Kaplan Executive Functioning System assessment in a sample of 264 native English-speaking children between the ages of 9 and 15 years. We also tested for measurement invariance for these items across age and gender groups using item response theory (IRT). Results of the exploratory factor analysis indicated that a two-factor model that distinguished between verbal and perceptual items provided the best fit to the data. Although the items demonstrated measurement invariance across age groups, measurement invariance was violated for gender groups, with two items demonstrating differential item functioning for males and females. Multigroup analysis using all 16 items indicated that the items were more effective for individuals whose IRT scale scores were relatively high. A single-group explanatory IRT model using 14 non-differential item functioning items showed that for perceptual ability, females scored higher than males and that scores increased with age for both males and females; for verbal ability, the observed increase in scores across age differed for males and females. The implications of these findings are discussed.

On the Complexity of Item Response Theory Models.

PubMed

Bonifay, Wes; Cai, Li

2017-01-01

Complexity in item response theory (IRT) has traditionally been quantified by simply counting the number of freely estimated parameters in the model. However, complexity is also contingent upon the functional form of the model. We examined four popular IRT models-exploratory factor analytic, bifactor, DINA, and DINO-with different functional forms but the same number of free parameters. In comparison, a simpler (unidimensional 3PL) model was specified such that it had 1 more parameter than the previous models. All models were then evaluated according to the minimum description length principle. Specifically, each model was fit to 1,000 data sets that were randomly and uniformly sampled from the complete data space and then assessed using global and item-level fit and diagnostic measures. The findings revealed that the factor analytic and bifactor models possess a strong tendency to fit any possible data. The unidimensional 3PL model displayed minimal fitting propensity, despite the fact that it included an additional free parameter. The DINA and DINO models did not demonstrate a proclivity to fit any possible data, but they did fit well to distinct data patterns. Applied researchers and psychometricians should therefore consider functional form-and not goodness-of-fit alone-when selecting an IRT model.

An Assessment of the Icing Blade and the SEA Multi-Element Sensor for Liquid Water Content Calibration of the NASA GRC Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith F.

2016-01-01

The Icing Research Tunnel at NASA Glenn has recently switched from using the Icing Blade to using the SEA Multi-Element Sensor (also known as the multi-wire) for its calibration of cloud liquid water content. In order to peform this transition, tests were completed to compare the Multi-Element Sensor to the Icing Blade, particularly with respect to liquid water content, airspeed, and drop size. The two instruments were found to compare well for the majority of Appendix C conditions. However, it was discovered that the Icing Blade under-measures when the conditions approach the Ludlam Limit. This paper also describes data processing procedures for the Multi-Element Sensor in the IRT, including collision efficiency corrections, mounting underneath a splitter plate, and correcting for a jump in the compensation wire power. Further data is presented to describe the repeatability of the IRT with the Multi-Element Sensor, health-monitoring checks for the instrument, and a sensing-element configuration comparison. Ultimately these tests showed that in the IRT, the multi-wire is a better instrument for measuring cloud liquid water content than the blade.

Development of the Abbreviated Masculine Gender Role Stress Scale

PubMed Central

Swartout, Kevin M.; Parrott, Dominic J.; Cohn, Amy M.; Hagman, Brett T.; Gallagher, Kathryn E.

2014-01-01

Data gathered from six independent samples (n = 1,729) that assessed men’s masculine gender role stress in college and community males were aggregated used to determine the reliability and validity of an abbreviated version of the Masculine Gender Role Stress Scale (MGRS scale). The 15 items with the highest item-to-total scale correlations were used to create an abbreviated MGRS scale. Psychometric properties of each of the 15-items were examined with Item Response Theory (IRT) analysis, using the discrimination and threshold parameters. IRT results showed that the abbreviated scale may hold promise at capturing the same amount of information as the full 40-item scale. Relative to the 40-item scale, the total score of the abbreviated MGRS scale demonstrated comparable convergent validity using the measurement domains of masculine identity, hyper-masculinity, trait anger, anger expression, and alcohol involvement. An abbreviated MGRS scale may be recommended for use in clinical practice and research settings to reduce cost, time, and patient/participant burden. Additionally, IRT analyses identified items with higher discrimination and threshold parameters that may be used to screen for problematic gender role stress in men who may be seen in routine clinical or medical practice. PMID:25528163

Human instrumental performance in ratio and interval contingencies: A challenge for associative theory.

PubMed

Pérez, Omar D; Aitken, Michael R F; Zhukovsky, Peter; Soto, Fabián A; Urcelay, Gonzalo P; Dickinson, Anthony

2016-12-15

Associative learning theories regard the probability of reinforcement as the critical factor determining responding. However, the role of this factor in instrumental conditioning is not completely clear. In fact, free-operant experiments show that participants respond at a higher rate on variable ratio than on variable interval schedules even though the reinforcement probability is matched between the schedules. This difference has been attributed to the differential reinforcement of long inter-response times (IRTs) by interval schedules, which acts to slow responding. In the present study, we used a novel experimental design to investigate human responding under random ratio (RR) and regulated probability interval (RPI) schedules, a type of interval schedule that sets a reinforcement probability independently of the IRT duration. Participants responded on each type of schedule before a final choice test in which they distributed responding between two schedules similar to those experienced during training. Although response rates did not differ during training, the participants responded at a lower rate on the RPI schedule than on the matched RR schedule during the choice test. This preference cannot be attributed to a higher probability of reinforcement for long IRTs and questions the idea that similar associative processes underlie classical and instrumental conditioning.

Precise determination of the heat delivery during in vivo magnetic nanoparticle hyperthermia with infrared thermography

NASA Astrophysics Data System (ADS)

Rodrigues, Harley F.; Capistrano, Gustavo; Mello, Francyelli M.; Zufelato, Nicholas; Silveira-Lacerda, Elisângela; Bakuzis, Andris F.

2017-05-01

Non-invasive and real-time monitoring of the heat delivery during magnetic nanoparticle hyperthermia (MNH) is of fundamental importance to predict clinical outcomes for cancer treatment. Infrared thermography (IRT) can determine the surface temperature due to three-dimensional heat delivery inside a subcutaneous tumor, an argument that is supported by numerical simulations. However, for precise temperature determination, it is of crucial relevance to use a correct experimental configuration. This work reports an MNH study using a sarcoma 180 murine tumor containing 3.9 mg of intratumorally injected manganese-ferrite nanoparticles. MNH was performed at low field amplitude and non-uniform field configuration. Five 30 min in vivo magnetic hyperthermia experiments were performed, monitoring the surface temperature with a fiber optical sensor and thermal camera at distinct angles with respect to the animal’s surface. The results indicate that temperature errors as large as 7~\\circ C can occur if the experiment is not properly designed. A new IRT error model is found to explain the data. More importantly, we show how to precisely monitor temperature with IRT during hyperthermia, which could positively impact heat dosimetry and clinical planning.

Precise determination of the heat delivery during in vivo magnetic nanoparticle hyperthermia with infrared thermography.

PubMed

Rodrigues, Harley F; Capistrano, Gustavo; Mello, Francyelli M; Zufelato, Nicholas; Silveira-Lacerda, Elisângela; Bakuzis, Andris F

2017-05-21

Non-invasive and real-time monitoring of the heat delivery during magnetic nanoparticle hyperthermia (MNH) is of fundamental importance to predict clinical outcomes for cancer treatment. Infrared thermography (IRT) can determine the surface temperature due to three-dimensional heat delivery inside a subcutaneous tumor, an argument that is supported by numerical simulations. However, for precise temperature determination, it is of crucial relevance to use a correct experimental configuration. This work reports an MNH study using a sarcoma 180 murine tumor containing 3.9 mg of intratumorally injected manganese-ferrite nanoparticles. MNH was performed at low field amplitude and non-uniform field configuration. Five 30 min in vivo magnetic hyperthermia experiments were performed, monitoring the surface temperature with a fiber optical sensor and thermal camera at distinct angles with respect to the animal's surface. The results indicate that temperature errors as large as [Formula: see text]C can occur if the experiment is not properly designed. A new IRT error model is found to explain the data. More importantly, we show how to precisely monitor temperature with IRT during hyperthermia, which could positively impact heat dosimetry and clinical planning.

An item response theory analysis of the Olweus Bullying scale.

PubMed

Breivik, Kyrre; Olweus, Dan

2014-12-02

In the present article, we used IRT (graded response) modeling as a useful technology for a detailed and refined study of the psychometric properties of the various items of the Olweus Bullying scale and the scale itself. The sample consisted of a very large number of Norwegian 4th-10th grade students (n = 48 926). The IRT analyses revealed that the scale was essentially unidimensional and had excellent reliability in the upper ranges of the latent bullying tendency trait, as intended and desired. Gender DIF effects were identified with regard to girls' use of indirect bullying by social exclusion and boys' use of physical bullying by hitting and kicking but these effects were small and worked in opposite directions, having negligible effects at the scale level. Also scale scores adjusted for DIF effects differed very little from non-adjusted scores. In conclusion, the empirical data were well characterized by the chosen IRT model and the Olweus Bullying scale was considered well suited for the conduct of fair and reliable comparisons involving different gender-age groups. Information Aggr. Behav. 9999:XX-XX, 2014. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

An item response theory analysis of the Olweus Bullying scale.

PubMed

Breivik, Kyrre; Olweus, Dan

2015-01-01

In the present article, we used IRT (graded response) modeling as a useful technology for a detailed and refined study of the psychometric properties of the various items of the Olweus Bullying scale and the scale itself. The sample consisted of a very large number of Norwegian 4th-10th grade students (n = 48 926). The IRT analyses revealed that the scale was essentially unidimensional and had excellent reliability in the upper ranges of the latent bullying tendency trait, as intended and desired. Gender DIF effects were identified with regard to girls' use of indirect bullying by social exclusion and boys' use of physical bullying by hitting and kicking but these effects were small and worked in opposite directions, having negligible effects at the scale level. Also scale scores adjusted for DIF effects differed very little from non-adjusted scores. In conclusion, the empirical data were well characterized by the chosen IRT model and the Olweus Bullying scale was considered well suited for the conduct of fair and reliable comparisons involving different gender-age groups. Information Aggr. Behav. 41:1-13, 2015. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

Development of the Abbreviated Masculine Gender Role Stress Scale.

PubMed

Swartout, Kevin M; Parrott, Dominic J; Cohn, Amy M; Hagman, Brett T; Gallagher, Kathryn E

2015-06-01

Data gathered from 6 independent samples (n = 1,729) that assessed men's masculine gender role stress in college and community males were aggregated used to determine the reliability and validity of an abbreviated version of the Masculine Gender Role Stress (MGRS) Scale. The 15 items with the highest item-to-total scale correlations were used to create an abbreviated MGRS Scale. Psychometric properties of each of the 15 items were examined with item response theory (IRT) analysis, using the discrimination and threshold parameters. IRT results showed that the abbreviated scale may hold promise at capturing the same amount of information as the full 40-item scale. Relative to the 40-item scale, the total score of the abbreviated MGRS Scale demonstrated comparable convergent validity using the measurement domains of masculine identity, hypermasculinity, trait anger, anger expression, and alcohol involvement. An abbreviated MGRS Scale may be recommended for use in clinical practice and research settings to reduce cost, time, and patient/participant burden. Additionally, IRT analyses identified items with higher discrimination and threshold parameters that may be used to screen for problematic gender role stress in men who may be seen in routine clinical or medical practice. (c) 2015 APA, all rights reserved).

Study of O-Phosphorylation Sites in Proteins Involved in Photosynthesis-Related Processes in Synechocystis sp. Strain PCC 6803: Application of the SRM Approach.

PubMed

Angeleri, Martina; Muth-Pawlak, Dorota; Aro, Eva-Mari; Battchikova, Natalia

2016-12-02

O-Phosphorylation has been shown in photosynthesis-related proteins in a cyanobacterium Synechocystis sp. strain PCC 6803 (thereafter Synechocystis 6803), suggesting that phosphorylation of S, T, and Y residues might be important in photosynthesis-related processes. Investigation of biological roles of these phosphorylation events requires confident knowledge of the phosphorylated sites and prospects for their individual assessment. We performed phosphoproteomic analysis of Synechocystis 6803 using TiO 2 enrichment of the phosphopeptides, followed by LC-MS/MS, and discovered 367 phosphorylation sites in 190 proteins participating in various cellular functions. Furthermore, we focused on the large group of phosphoproteins that are involved in light harvesting, photosynthesis-driven electron flow, photoprotection, and CO 2 fixation. The SRM approach was applied to verify/improve assignments of phosphorylation sites in these proteins and to investigate possibilities for analysis of phosphopeptide isomers. The SRM assays were designed for peptides comprising 45 phosphorylation sites. The assays contain peptide iRT values and Q1/Q3 transitions comprising those discriminating between phosphopeptide isoforms. The majority of investigated phosphopeptides and phosphorylated isoforms could be individually assessed with the SRM technique. The assays could be potentially used in future quantitative studies to evaluate an extent of phosphorylation in photosynthesis-related proteins in Synechocystis 6803 cells challenged with various environmental stresses.

Measurement Equivalence of the Patient Reported Outcomes Measurement Information System® (PROMIS®) Applied Cognition – General Concerns, Short Forms in Ethnically Diverse Groups

PubMed Central

Fieo, Robert; Ocepek-Welikson, Katja; Kleinman, Marjorie; Eimicke, Joseph P.; Crane, Paul K.; Cella, David; Teresi, Jeanne A.

2017-01-01

Aims The goals of these analyses were to examine the psychometric properties and measurement equivalence of a self-reported cognition measure, the Patient Reported Outcome Measurement Information System® (PROMIS®) Applied Cognition – General Concerns short form. These items are also found in the PROMIS Cognitive Function (version 2) item bank. This scale consists of eight items related to subjective cognitive concerns. Differential item functioning (DIF) analyses of gender, education, race, age, and (Spanish) language were performed using an ethnically diverse sample (n = 5,477) of individuals with cancer. This is the first analysis examining DIF in this item set across ethnic and racial groups. Methods DIF hypotheses were derived by asking content experts to indicate whether they posited DIF for each item and to specify the direction. The principal DIF analytic model was item response theory (IRT) using the graded response model for polytomous data, with accompanying Wald tests and measures of magnitude. Sensitivity analyses were conducted using ordinal logistic regression (OLR) with a latent conditioning variable. IRT-based reliability, precision and information indices were estimated. Results DIF was identified consistently only for the item, brain not working as well as usual. After correction for multiple comparisons, this item showed significant DIF for both the primary and sensitivity analyses. Black respondents and Hispanics in comparison to White non-Hispanic respondents evidenced a lower conditional probability of endorsing the item, brain not working as well as usual. The same pattern was observed for the education grouping variable: as compared to those with a graduate degree, conditioning on overall level of subjective cognitive concerns, those with less than high school education also had a lower probability of endorsing this item. DIF was also observed for age for two items after correction for multiple comparisons for both the IRT and OLR-based models: “I have had to work really hard to pay attention or I would make a mistake” and “I have had trouble shifting back and forth between different activities that require thinking”. For both items, conditional on cognitive complaints, older respondents had a higher likelihood than younger respondents of endorsing the item in the cognitive complaints direction. The magnitude and impact of DIF was minimal. The scale showed high precision along much of the subjective cognitive concerns continuum; the overall IRT-based reliability estimate for the total sample was 0.88 and the estimates for subgroups ranged from 0.87 to 0.92. Conclusion Little DIF of high magnitude or impact was observed in the PROMIS Applied Cognition – General Concerns short form item set. One item, “It has seemed like my brain was not working as well as usual” might be singled out for further study. However, in general the short form item set was highly reliable, informative, and invariant across differing race/ethnic, educational, age, gender, and language groups. PMID:28523238

Measurement Equivalence of the Patient Reported Outcomes Measurement Information System® (PROMIS®) Applied Cognition - General Concerns, Short Forms in Ethnically Diverse Groups.

PubMed

Fieo, Robert; Ocepek-Welikson, Katja; Kleinman, Marjorie; Eimicke, Joseph P; Crane, Paul K; Cella, David; Teresi, Jeanne A

2016-01-01

The goals of these analyses were to examine the psychometric properties and measurement equivalence of a self-reported cognition measure, the Patient Reported Outcome Measurement Information System ® (PROMIS ® ) Applied Cognition - General Concerns short form. These items are also found in the PROMIS Cognitive Function (version 2) item bank. This scale consists of eight items related to subjective cognitive concerns. Differential item functioning (DIF) analyses of gender, education, race, age, and (Spanish) language were performed using an ethnically diverse sample ( n = 5,477) of individuals with cancer. This is the first analysis examining DIF in this item set across ethnic and racial groups. DIF hypotheses were derived by asking content experts to indicate whether they posited DIF for each item and to specify the direction. The principal DIF analytic model was item response theory (IRT) using the graded response model for polytomous data, with accompanying Wald tests and measures of magnitude. Sensitivity analyses were conducted using ordinal logistic regression (OLR) with a latent conditioning variable. IRT-based reliability, precision and information indices were estimated. DIF was identified consistently only for the item, brain not working as well as usual. After correction for multiple comparisons, this item showed significant DIF for both the primary and sensitivity analyses. Black respondents and Hispanics in comparison to White non-Hispanic respondents evidenced a lower conditional probability of endorsing the item, brain not working as well as usual. The same pattern was observed for the education grouping variable: as compared to those with a graduate degree, conditioning on overall level of subjective cognitive concerns, those with less than high school education also had a lower probability of endorsing this item. DIF was also observed for age for two items after correction for multiple comparisons for both the IRT and OLR-based models: "I have had to work really hard to pay attention or I would make a mistake" and "I have had trouble shifting back and forth between different activities that require thinking". For both items, conditional on cognitive complaints, older respondents had a higher likelihood than younger respondents of endorsing the item in the cognitive complaints direction. The magnitude and impact of DIF was minimal. The scale showed high precision along much of the subjective cognitive concerns continuum; the overall IRT-based reliability estimate for the total sample was 0.88 and the estimates for subgroups ranged from 0.87 to 0.92. Little DIF of high magnitude or impact was observed in the PROMIS Applied Cognition - General Concerns short form item set. One item, "It has seemed like my brain was not working as well as usual" might be singled out for further study. However, in general the short form item set was highly reliable, informative, and invariant across differing race/ethnic, educational, age, gender, and language groups.

Extending the Limits of Quantitative Proteome Profiling with Data-Independent Acquisition and Application to Acetaminophen-Treated Three-Dimensional Liver Microtissues*

PubMed Central

Bruderer, Roland; Bernhardt, Oliver M.; Gandhi, Tejas; Miladinović, Saša M.; Cheng, Lin-Yang; Messner, Simon; Ehrenberger, Tobias; Zanotelli, Vito; Butscheid, Yulia; Escher, Claudia; Vitek, Olga; Rinner, Oliver; Reiter, Lukas

2015-01-01

The data-independent acquisition (DIA) approach has recently been introduced as a novel mass spectrometric method that promises to combine the high content aspect of shotgun proteomics with the reproducibility and precision of selected reaction monitoring. Here, we evaluate, whether SWATH-MS type DIA effectively translates into a better protein profiling as compared with the established shotgun proteomics. We implemented a novel DIA method on the widely used Orbitrap platform and used retention-time-normalized (iRT) spectral libraries for targeted data extraction using Spectronaut. We call this combination hyper reaction monitoring (HRM). Using a controlled sample set, we show that HRM outperformed shotgun proteomics both in the number of consistently identified peptides across multiple measurements and quantification of differentially abundant proteins. The reproducibility of HRM in peptide detection was above 98%, resulting in quasi complete data sets compared with 49% of shotgun proteomics. Utilizing HRM, we profiled acetaminophen (APAP)1-treated three-dimensional human liver microtissues. An early onset of relevant proteome changes was revealed at subtoxic doses of APAP. Further, we detected and quantified for the first time human NAPQI-protein adducts that might be relevant for the toxicity of APAP. The adducts were identified on four mitochondrial oxidative stress related proteins (GATM, PARK7, PRDX6, and VDAC2) and two other proteins (ANXA2 and FTCD). Our findings imply that DIA should be the preferred method for quantitative protein profiling. PMID:25724911

A modular approach for item response theory modeling with the R package flirt.

PubMed

Jeon, Minjeong; Rijmen, Frank

2016-06-01

The new R package flirt is introduced for flexible item response theory (IRT) modeling of psychological, educational, and behavior assessment data. flirt integrates a generalized linear and nonlinear mixed modeling framework with graphical model theory. The graphical model framework allows for efficient maximum likelihood estimation. The key feature of flirt is its modular approach to facilitate convenient and flexible model specifications. Researchers can construct customized IRT models by simply selecting various modeling modules, such as parametric forms, number of dimensions, item and person covariates, person groups, link functions, etc. In this paper, we describe major features of flirt and provide examples to illustrate how flirt works in practice.

Development and Standardization of the Diagnostic Adaptive Behavior Scale: Application of Item Response Theory to the Assessment of Adaptive Behavior.

PubMed

Tassé, Marc J; Schalock, Robert L; Thissen, David; Balboni, Giulia; Bersani, Henry Hank; Borthwick-Duffy, Sharon A; Spreat, Scott; Widaman, Keith F; Zhang, Dalun; Navas, Patricia

2016-03-01

The Diagnostic Adaptive Behavior Scale (DABS) was developed using item response theory (IRT) methods and was constructed to provide the most precise and valid adaptive behavior information at or near the cutoff point of making a decision regarding a diagnosis of intellectual disability. The DABS initial item pool consisted of 260 items. Using IRT modeling and a nationally representative standardization sample, the item set was reduced to 75 items that provide the most precise adaptive behavior information at the cutoff area determining the presence or not of significant adaptive behavior deficits across conceptual, social, and practical skills. The standardization of the DABS is described and discussed.

Equal Area Logistic Estimation for Item Response Theory

NASA Astrophysics Data System (ADS)

Lo, Shih-Ching; Wang, Kuo-Chang; Chang, Hsin-Li

2009-08-01

Item response theory (IRT) models use logistic functions exclusively as item response functions (IRFs). Applications of IRT models require obtaining the set of values for logistic function parameters that best fit an empirical data set. However, success in obtaining such set of values does not guarantee that the constructs they represent actually exist, for the adequacy of a model is not sustained by the possibility of estimating parameters. In this study, an equal area based two-parameter logistic model estimation algorithm is proposed. Two theorems are given to prove that the results of the algorithm are equivalent to the results of fitting data by logistic model. Numerical results are presented to show the stability and accuracy of the algorithm.

Multidimensional student skills with collaborative filtering

NASA Astrophysics Data System (ADS)

Bergner, Yoav; Rayyan, Saif; Seaton, Daniel; Pritchard, David E.

2013-01-01

Despite the fact that a physics course typically culminates in one final grade for the student, many instructors and researchers believe that there are multiple skills that students acquire to achieve mastery. Assessment validation and data analysis in general may thus benefit from extension to multidimensional ability. This paper introduces an approach for model determination and dimensionality analysis using collaborative filtering (CF), which is related to factor analysis and item response theory (IRT). Model selection is guided by machine learning perspectives, seeking to maximize the accuracy in predicting which students will answer which items correctly. We apply the CF to response data for the Mechanics Baseline Test and combine the results with prior analysis using unidimensional IRT.

Using R and WinBUGS to fit a Generalized Partial Credit Model for developing and evaluating patient-reported outcomes assessments

PubMed Central

Li, Yuelin; Baser, Ray

2013-01-01

The US Food and Drug Administration recently announced the final guidelines on the development and validation of Patient-Reported Outcomes (PROs) assessments in drug labeling and clinical trials. This guidance paper may boost the demand for new PRO survey questionnaires. Henceforth biostatisticians may encounter psychometric methods more frequently, particularly Item Response Theory (IRT) models to guide the shortening of a PRO assessment instrument. This article aims to provide an introduction on the theory and practical analytic skills in fitting a Generalized Partial Credit Model in IRT (GPCM). GPCM theory is explained first, with special attention to a clearer exposition of the formal mathematics than what is typically available in the psychometric literature. Then a worked example is presented, using self-reported responses taken from the International Personality Item Pool. The worked example contains step-by-step guides on using the statistical languages R and WinBUGS in fitting the GPCM. Finally, the Fisher information function of the GPCM model is derived and used to evaluate, as an illustrative example, the usefulness of assessment items by their information contents. This article aims to encourage biostatisticians to apply IRT models in the re-analysis of existing data and in future research. PMID:22362655

Using R and WinBUGS to fit a generalized partial credit model for developing and evaluating patient-reported outcomes assessments.

PubMed

Li, Yuelin; Baser, Ray

2012-08-15

The US Food and Drug Administration recently announced the final guidelines on the development and validation of patient-reported outcomes (PROs) assessments in drug labeling and clinical trials. This guidance paper may boost the demand for new PRO survey questionnaires. Henceforth, biostatisticians may encounter psychometric methods more frequently, particularly item response theory (IRT) models to guide the shortening of a PRO assessment instrument. This article aims to provide an introduction on the theory and practical analytic skills in fitting a generalized partial credit model (GPCM) in IRT. GPCM theory is explained first, with special attention to a clearer exposition of the formal mathematics than what is typically available in the psychometric literature. Then, a worked example is presented, using self-reported responses taken from the international personality item pool. The worked example contains step-by-step guides on using the statistical languages r and WinBUGS in fitting the GPCM. Finally, the Fisher information function of the GPCM model is derived and used to evaluate, as an illustrative example, the usefulness of assessment items by their information contents. This article aims to encourage biostatisticians to apply IRT models in the re-analysis of existing data and in future research. Copyright © 2012 John Wiley & Sons, Ltd.

An item response curves analysis of the Force Concept Inventory

NASA Astrophysics Data System (ADS)

Morris, Gary A.; Harshman, Nathan; Branum-Martin, Lee; Mazur, Eric; Mzoughi, Taha; Baker, Stephen D.

2012-09-01

Several years ago, we introduced the idea of item response curves (IRC), a simplistic form of item response theory (IRT), to the physics education research community as a way to examine item performance on diagnostic instruments such as the Force Concept Inventory (FCI). We noted that a full-blown analysis using IRT would be a next logical step, which several authors have since taken. In this paper, we show that our simple approach not only yields similar conclusions in the analysis of the performance of items on the FCI to the more sophisticated and complex IRT analyses but also permits additional insights by characterizing both the correct and incorrect answer choices. Our IRC approach can be applied to a variety of multiple-choice assessments but, as applied to a carefully designed instrument such as the FCI, allows us to probe student understanding as a function of ability level through an examination of each answer choice. We imagine that physics teachers could use IRC analysis to identify prominent misconceptions and tailor their instruction to combat those misconceptions, fulfilling the FCI authors' original intentions for its use. Furthermore, the IRC analysis can assist test designers to improve their assessments by identifying nonfunctioning distractors that can be replaced with distractors attractive to students at various ability levels.

The Communicative Participation Item Bank (CPIB): Item bank calibration and development of a disorder-generic short form

PubMed Central

Baylor, Carolyn; Yorkston, Kathryn; Eadie, Tanya; Kim, Jiseon; Chung, Hyewon; Amtmann, Dagmar

2015-01-01

Purpose The purpose of this study was to calibrate the items for the Communicative Participation Item Bank (CPIB) using Item Response Theory (IRT). One overriding objective was to examine if the IRT item parameters would be consistent across different diagnostic groups, thereby allowing creation of a disorder-generic instrument. The intended outcomes were the final item bank and a short form ready for clinical and research applications. Methods Self-report data were collected from 701 individuals representing four diagnoses: multiple sclerosis, Parkinson’s disease, amyotrophic lateral sclerosis and head and neck cancer. Participants completed the CPIB and additional self-report questionnaires. CPIB data were analyzed using the IRT Graded Response Model (GRM). Results The initial set of 94 candidate CPIB items were reduced to an item bank of 46 items demonstrating unidimensionality, local independence, good item fit, and good measurement precision. Differential item function (DIF) analyses detected no meaningful differences across diagnostic groups. A 10-item, disorder-generic short form was generated. Conclusions The CPIB provides speech-language pathologists with a unidimensional, self-report outcomes measurement instrument dedicated to the construct of communicative participation. This instrument may be useful to clinicians and researchers wanting to implement measures of communicative participation in their work. PMID:23816661

Aero-Thermal Calibration of the NASA Glenn Icing Research Tunnel (2012 Test)

NASA Technical Reports Server (NTRS)

Pastor-Barsi, Christine M.; Arrington, E. Allen; VanZante, Judith Foss

2012-01-01

A major modification of the refrigeration plant and heat exchanger at the NASA Glenn Icing Research Tunnel (IRT) occurred in autumn of 2011. It is standard practice at NASA Glenn to perform a full aero-thermal calibration of the test section of a wind tunnel facility upon completion of major modifications. This paper will discuss the tools and techniques used to complete an aero-thermal calibration of the IRT and the results that were acquired. The goal of this test entry was to complete a flow quality survey and aero-thermal calibration measurements in the test section of the IRT. Test hardware that was used includes the 2D Resistive Temperature Detector (RTD) array, 9-ft pressure survey rake, hot wire survey rake, and the quick check survey rake. This test hardware provides a map of the velocity, Mach number, total and static pressure, total temperature, flow angle and turbulence intensity. The data acquired were then reduced to examine pressure, temperature, velocity, flow angle, and turbulence intensity. Reduced data has been evaluated to assess how the facility meets flow quality goals. No icing conditions were tested as part of the aero-thermal calibration. However, the effects of the spray bar air injections on the flow quality and aero-thermal calibration measurements were examined as part of this calibration.

Measuring stigma after spinal cord injury: Development and psychometric characteristics of the SCI-QOL Stigma item bank and short form.

PubMed

Kisala, Pamela A; Tulsky, David S; Pace, Natalie; Victorson, David; Choi, Seung W; Heinemann, Allen W

2015-05-01

To develop a calibrated item bank and computer adaptive test (CAT) to assess the effects of stigma on health-related quality of life in individuals with spinal cord injury (SCI). Grounded-theory based qualitative item development methods, large-scale item calibration field testing, confirmatory factor analysis, and item response theory (IRT)-based psychometric analyses. Five SCI Model System centers and one Department of Veterans Affairs medical center in the United States. Adults with traumatic SCI. SCI-QOL Stigma Item Bank A sample of 611 individuals with traumatic SCI completed 30 items assessing SCI-related stigma. After 7 items were iteratively removed, factor analyses confirmed a unidimensional pool of items. Graded Response Model IRT analyses were used to estimate slopes and thresholds for the final 23 items. The SCI-QOL Stigma item bank is unique not only in the assessment of SCI-related stigma but also in the inclusion of individuals with SCI in all phases of its development. Use of confirmatory factor analytic and IRT methods provide flexibility and precision of measurement. The item bank may be administered as a CAT or as a 10-item fixed-length short form and can be used for research and clinical applications.

The Montgomery Äsberg and the Hamilton Ratings of Depression

PubMed Central

Carmody, Thomas; Rush, A. John; Bernstein, Ira; Warden, Diane; Brannan, Stephen; Burnham, Daniel; Woo, Ada; Trivedi, Madhukar

2007-01-01

The 17-item Hamilton Rating Scale for Depression (HRSD17) and the Montgomery Äsberg Depression Rating Scale (MADRS) are two widely used clinicianrated symptom scales. A 6-item version of the HRSD (HRSD6) was created by Bech to address the psychometric limitations of the HRSD17. The psychometric properties of these measures were compared using classical test theory (CTT) and item response theory (IRT) methods. IRT methods were used to equate total scores on any two scales. Data from two distinctly different outpatient studies of nonpsychotic major depression: a 12-month study of highly treatment-resistant patients (n=233) and an 8-week acute phase drug treatment trial (n=985) were used for robustness of results. MADRS and HRSD6 items generally contributed more to the measurement of depression than HRSD17 items as shown by higher item-total correlations and higher IRT slope parameters. The MADRS and HRSD6 were unifactorial while the HRSD17 contained 2 factors. The MADRS showed about twice the precision in estimating depression as either the HRSD17 or HRSD6 for average severity of depression. An HRSD17 of 7 corresponded to an 8 or 9 on the MADRS and 4 on the HRSD6. The MADRS would be superior to the HRSD17 in the conduct of clinical trials. PMID:16769204

The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K. Empirical relations to convert Ca II infrared triplet measurements to common activity indices

NASA Astrophysics Data System (ADS)

Martin, J.; Fuhrmeister, B.; Mittag, M.; Schmidt, T. O. B.; Hempelmann, A.; González-Pérez, J. N.; Schmitt, J. H. M. M.

2017-09-01

Aims: A large number of Calcium infrared triplet (IRT) spectra are expected from the Gaia and CARMENES missions. Conversion of these spectra into known activity indicators will allow analysis of their temporal evolution to a better degree. We set out to find such a conversion formula and to determine its robustness. Methods: We have compared 2274 Ca II IRT spectra of active main-sequence F to K stars taken by the TIGRE telescope with those of inactive stars of the same spectral type. After normalizing and applying rotational broadening, we subtracted the comparison spectra to find the chromospheric excess flux caused by activity. We obtained the total excess flux, and compared it to established activity indices derived from the Ca II H and K lines, the spectra of which were obtained simultaneously to the infrared spectra. Results: The excess flux in the Ca II IRT is found to correlate well with R'HK and R+HK, as well as SMWO, if the B - V-dependency is taken into account. We find an empirical conversion formula to calculate the corresponding value of one activity indicator from the measurement of another, by comparing groups of datapoints of stars with similar B - V.

Procedures to develop a computerized adaptive test to assess patient-reported physical functioning.

PubMed

McCabe, Erin; Gross, Douglas P; Bulut, Okan

2018-06-07

The purpose of this paper is to demonstrate the procedures to develop and implement a computerized adaptive patient-reported outcome (PRO) measure using secondary analysis of a dataset and items from fixed-format legacy measures. We conducted secondary analysis of a dataset of responses from 1429 persons with work-related lower extremity impairment. We calibrated three measures of physical functioning on the same metric, based on item response theory (IRT). We evaluated efficiency and measurement precision of various computerized adaptive test (CAT) designs using computer simulations. IRT and confirmatory factor analyses support combining the items from the three scales for a CAT item bank of 31 items. The item parameters for IRT were calculated using the generalized partial credit model. CAT simulations show that reducing the test length from the full 31 items to a maximum test length of 8 items, or 20 items is possible without a significant loss of information (95, 99% correlation with legacy measure scores). We demonstrated feasibility and efficiency of using CAT for PRO measurement of physical functioning. The procedures we outlined are straightforward, and can be applied to other PRO measures. Additionally, we have included all the information necessary to implement the CAT of physical functioning in the electronic supplementary material of this paper.

Close-up analysis of inflight ice accretion

NASA Technical Reports Server (NTRS)

Reehorst, Andrew L.; Ratvasky, Thomas P.; Sims, James

1994-01-01

The objective of this effort was to validate in flight, data that has been gathered in the NASA Lewis Research Center's Icing Research Tunnel (IRT) over the past several years. All data was acquired in flight on the NASA Lewis Research Center's Twin Otter Icing Research Aircraft. A faired 3.5 in. diameter metal-clad cylinder exposed to the natural icing environment was observed by a close-up video camera. The grazing angle video footage was recorded to S-VHS video tape and after the icing encounter, the resultant ice shape was documented by 35 mm photography and pencil tracings. The feather growth area was of primary interest; however, all regions of the ice accretion, from the stagnation line to the aft edge of run back were observed and recorded. After analysis of the recorded data several interesting points became evident: (1) the measured flight feather growth rate is consistent with IRT values, (2) the feather growth rate appears to be influenced by droplet size, (3) the feathers were straighter in the lower, spottier LWC of flight in comparison to those observed in the IRT, (4) feather shedding and ice sublimation may be significant to the final ice shape, and (5) the snow encountered on these flights appeared to have little influence on ice growth.

Assessment of health surveys: fitting a multidimensional graded response model.

PubMed

Depaoli, Sarah; Tiemensma, Jitske; Felt, John M

The multidimensional graded response model, an item response theory (IRT) model, can be used to improve the assessment of surveys, even when sample sizes are restricted. Typically, health-based survey development utilizes classical statistical techniques (e.g. reliability and factor analysis). In a review of four prominent journals within the field of Health Psychology, we found that IRT-based models were used in less than 10% of the studies examining scale development or assessment. However, implementing IRT-based methods can provide more details about individual survey items, which is useful when determining the final item content of surveys. An example using a quality of life survey for Cushing's syndrome (CushingQoL) highlights the main components for implementing the multidimensional graded response model. Patients with Cushing's syndrome (n = 397) completed the CushingQoL. Results from the multidimensional graded response model supported a 2-subscale scoring process for the survey. All items were deemed as worthy contributors to the survey. The graded response model can accommodate unidimensional or multidimensional scales, be used with relatively lower sample sizes, and is implemented in free software (example code provided in online Appendix). Use of this model can help to improve the quality of health-based scales being developed within the Health Sciences.

Measuring stigma after spinal cord injury: Development and psychometric characteristics of the SCI-QOL Stigma item bank and short form

PubMed Central

Kisala, Pamela A.; Tulsky, David S.; Pace, Natalie; Victorson, David; Choi, Seung W.; Heinemann, Allen W.

2015-01-01

Objective To develop a calibrated item bank and computer adaptive test (CAT) to assess the effects of stigma on health-related quality of life in individuals with spinal cord injury (SCI). Design Grounded-theory based qualitative item development methods, large-scale item calibration field testing, confirmatory factor analysis, and item response theory (IRT)-based psychometric analyses. Setting Five SCI Model System centers and one Department of Veterans Affairs medical center in the United States. Participants Adults with traumatic SCI. Main Outcome Measures SCI-QOL Stigma Item Bank Results A sample of 611 individuals with traumatic SCI completed 30 items assessing SCI-related stigma. After 7 items were iteratively removed, factor analyses confirmed a unidimensional pool of items. Graded Response Model IRT analyses were used to estimate slopes and thresholds for the final 23 items. Conclusions The SCI-QOL Stigma item bank is unique not only in the assessment of SCI-related stigma but also in the inclusion of individuals with SCI in all phases of its development. Use of confirmatory factor analytic and IRT methods provide flexibility and precision of measurement. The item bank may be administered as a CAT or as a 10-item fixed-length short form and can be used for research and clinical applications. PMID:26010973

General mixture item response models with different item response structures: Exposition with an application to Likert scales.

PubMed

Tijmstra, Jesper; Bolsinova, Maria; Jeon, Minjeong

2018-01-10

This article proposes a general mixture item response theory (IRT) framework that allows for classes of persons to differ with respect to the type of processes underlying the item responses. Through the use of mixture models, nonnested IRT models with different structures can be estimated for different classes, and class membership can be estimated for each person in the sample. If researchers are able to provide competing measurement models, this mixture IRT framework may help them deal with some violations of measurement invariance. To illustrate this approach, we consider a two-class mixture model, where a person's responses to Likert-scale items containing a neutral middle category are either modeled using a generalized partial credit model, or through an IRTree model. In the first model, the middle category ("neither agree nor disagree") is taken to be qualitatively similar to the other categories, and is taken to provide information about the person's endorsement. In the second model, the middle category is taken to be qualitatively different and to reflect a nonresponse choice, which is modeled using an additional latent variable that captures a person's willingness to respond. The mixture model is studied using simulation studies and is applied to an empirical example.

Use of non-parametric item response theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS).

PubMed

Khan, Anzalee; Lewis, Charles; Lindenmayer, Jean-Pierre

2011-11-16

Nonparametric item response theory (IRT) was used to examine (a) the performance of the 30 Positive and Negative Syndrome Scale (PANSS) items and their options ((levels of severity), (b) the effectiveness of various subscales to discriminate among differences in symptom severity, and (c) the development of an abbreviated PANSS (Mini-PANSS) based on IRT and a method to link scores to the original PANSS. Baseline PANSS scores from 7,187 patients with Schizophrenia or Schizoaffective disorder who were enrolled between 1995 and 2005 in psychopharmacology trials were obtained. Option characteristic curves (OCCs) and Item Characteristic Curves (ICCs) were constructed to examine the probability of rating each of seven options within each of 30 PANSS items as a function of subscale severity, and summed-score linking was applied to items selected for the Mini-PANSS. The majority of items forming the Positive and Negative subscales (i.e. 19 items) performed very well and discriminate better along symptom severity compared to the General Psychopathology subscale. Six of the seven Positive Symptom items, six of the seven Negative Symptom items, and seven out of the 16 General Psychopathology items were retained for inclusion in the Mini-PANSS. Summed score linking and linear interpolation was able to produce a translation table for comparing total subscale scores of the Mini-PANSS to total subscale scores on the original PANSS. Results show scores on the subscales of the Mini-PANSS can be linked to scores on the original PANSS subscales, with very little bias. The study demonstrated the utility of non-parametric IRT in examining the item properties of the PANSS and to allow selection of items for an abbreviated PANSS scale. The comparisons between the 30-item PANSS and the Mini-PANSS revealed that the shorter version is comparable to the 30-item PANSS, but when applying IRT, the Mini-PANSS is also a good indicator of illness severity.

Considerations for the independent reaction times and step-by-step methods for radiation chemistry simulations

NASA Astrophysics Data System (ADS)

Plante, Ianik; Devroye, Luc

2017-10-01

Ionizing radiation interacts with the water molecules of the tissues mostly by ionizations and excitations, which result in the formation of the radiation track structure and the creation of radiolytic species such as H.,.OH, H2, H2O2, and e-aq. After their creation, these species diffuse and may chemically react with the neighboring species and with the molecules of the medium. Therefore radiation chemistry is of great importance in radiation biology. As the chemical species are not distributed homogeneously, the use of conventional models of homogeneous reactions cannot completely describe the reaction kinetics of the particles. Actually, many simulations of radiation chemistry are done using the Independent Reaction Time (IRT) method, which is a very fast technique to calculate radiochemical yields but which do not calculate the positions of the radiolytic species as a function of time. Step-by-step (SBS) methods, which are able to provide such information, have been used only sparsely because these are time-consuming in terms of calculation. Recent improvements in computer performance now allow the regular use of the SBS method in radiation chemistry. The SBS and IRT methods are both based on the Green's functions of the diffusion equation (GFDE). In this paper, several sampling algorithms of the GFDE and for the IRT method are presented. We show that the IRT and SBS methods are exactly equivalent for 2-particles systems for diffusion and partially diffusion-controlled reactions between non-interacting particles. We also show that the results obtained with the SBS simulation method with periodic boundary conditions are in agreement with the predictions by classical reaction kinetics theory, which is an important step towards using this method for modelling of biochemical networks and metabolic pathways involved in oxidative stress. Finally, the first simulation results obtained with the code RITRACKS (Relativistic Ion Tracks) are presented.

An Item Response Theory (IRT) analysis of the Short Inventory of Problems-Alcohol and Drugs (SIP-AD) among non-treatment seeking men-who-have-sex-with-men: evidence for a shortened 10-item SIP-AD.

PubMed

Hagman, Brett T; Kuerbis, Alexis N; Morgenstern, Jon; Bux, Donald A; Parsons, Jeffrey T; Heidinger, Bram E

2009-11-01

The Short Inventory of Problems-Alcohol and Drugs (SIP-AD) is a 15-item measure that assesses concurrently negative consequences associated with alcohol and illicit drug use. Current psychometric evaluation has been limited to classical test theory (CTT) statistics, and it has not been validated among non-treatment seeking men-who-have-sex-with-men (MSM). Methods from Item Response Theory (IRT) can improve upon CTT by providing an in-depth analysis of how each item performs across the underlying latent trait that it is purported to measure. The present study examined the psychometric properties of the SIP-AD using methods from both IRT and CTT among a non-treatment seeking MSM sample (N=469). Participants were recruited from the New York City area and were asked to participate in a series of studies examining club drug use. Results indicated that five items on the SIP-AD demonstrated poor item misfit or significant differential item functioning (DIF) across race/ethnicity and HIV status. These five items were dropped and two-parameter IRT analyses were conducted on the remaining 10 items, which indicated a restricted range of item location parameters (-.15 to -.99) plotted at the lower end of the latent negative consequences severity continuum, and reasonably high discrimination parameters (1.30 to 2.22). Additional CTT statistics were compared between the original 15-item SIP-AD and the refined 10-item SIP-AD and suggest that the differences were negligible with the refined 10-item SIP-AD indicating a high degree of reliability and validity. Findings suggest the SIP-AD can be shortened to 10 items and appears to be a non-biased reliable and valid measure among non-treatment seeking MSM.

Optimizing post activation potentiation for explosive activities in competitive sports

PubMed Central

Gołaś, Artur; Maszczyk, Adam; Mikołajec, Kazimierz; Stastny, Petr

2016-01-01

Abstract Post activation potentiation (PAP) has shown improved performance during movements requiring large muscular power output following contractions under near maximal load conditions. PAP can be described as an acute enhancement of performance or an enhancement of factors determining an explosive sports activity following a preload stimulus. In practice, PAP has been achieved by complex training, which involves a combination of a heavy loaded exercise followed by a biomechanically similar explosive activity, best if specific for a particular sport discipline. The main objective of this study was to investigate the effects of PAP on performance in explosive motor activities specific for basketball, luge and athletics throws. The novel approach to the experiments included individualized recovery time (IRT) between the conditioning exercise and the explosive activity. Additionally, the research groups were homogenous and included only competitive athletes of similar age and training experience. Thirty one well trained athletes from 3 different sport disciplines participated in the study. All athletes performed a heavy loaded conditioning activity (80-130%1RM) followed by a biomechanically similar explosive exercise, during which power (W) or the rate of power development (W/s/kg) was evaluated. The results of our experiment confirmed the effectiveness of PAP with well-trained athlets during explosive motor activities such as jumping, throwing and pushing. Additionally, our research showed that eccentric supramaximal intensities (130% 1RM) can be effective in eliciting PAP in strength trained athletes. Our experiments also showed that the IRT should be individualized because athletes differ in the strength level, training experience and muscle fiber structure. In the three experiments conducted with basketball players, track and field athletes and luge athletes, the optimal IRT equaled 6 min. This justifies the need to individualize the volume and intensity of the CA, and especially the IRT, between the CA and the explosive activity. PMID:28149397

Presence of brown adipose tissue in an adolescent with severe primary hypothyroidism.

PubMed

Kim, Mimi S; Hu, Houchun H; Aggabao, Patricia C; Geffner, Mitchell E; Gilsanz, Vicente

2014-09-01

Brown adipose tissue (BAT) generates heat during adaptive thermogenesis in response to cold temperature. Thyroid hormone (TH) receptors, type 2 deiodinase, and TSH receptors are present on brown adipocytes, indicating that the thyroid axis regulates BAT. It is unknown whether absent TH in humans would down-regulate development of BAT and its thermogenic function. The objective of the study was to examine BAT by magnetic resonance imaging (MRI) and infrared thermal imaging (IRT) in a pediatric patient with severe primary hypothyroidism before and after TH treatment. This study was a case report with longitudinal follow-up in a tertiary center. BAT fat fraction (FF) by MRI and skin temperature by IRT were measured. An 11.5-year-old female was severely hypothyroid (TSH, 989 μIU/mL; free T4, 0.10 ng/dL; low thyroglobulin, 3.0 ng/mL). Low MRI measures of FF (56.1% ± 3.7%) indicated that BAT was abundantly present in the supraclavicular fossa. IRT showed higher supraclavicular temperature (36.0°C ±0.16°C) than the suprasternal area (34.3°C ± 0.19°C). After 2 months of TH replacement, she was euthyroid (TSH, 4.3 μIU/mL; free T4, 1.49 ng/dL; T3, 102 ng/dL) at which time supraclavicular BAT decreased (increased FF 60.7% ± 3.8%). IRT showed a higher, more homogeneous skin temperature throughout the upper thorax (supraclavicular, 37.1°C ± 0.23°C; suprasternal, 36.4°C ± 0.13°C). The overall size of the supraclavicular fat depot decreased from 84.79 cm(3) to 41.21 cm(3). These findings document the presence of BAT and thermogenesis in profound hypothyroidism and suggest a role for TSH and/or TRH as a potential regulator of BAT.

Use of NON-PARAMETRIC Item Response Theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS)

PubMed Central

2011-01-01

Background Nonparametric item response theory (IRT) was used to examine (a) the performance of the 30 Positive and Negative Syndrome Scale (PANSS) items and their options ((levels of severity), (b) the effectiveness of various subscales to discriminate among differences in symptom severity, and (c) the development of an abbreviated PANSS (Mini-PANSS) based on IRT and a method to link scores to the original PANSS. Methods Baseline PANSS scores from 7,187 patients with Schizophrenia or Schizoaffective disorder who were enrolled between 1995 and 2005 in psychopharmacology trials were obtained. Option characteristic curves (OCCs) and Item Characteristic Curves (ICCs) were constructed to examine the probability of rating each of seven options within each of 30 PANSS items as a function of subscale severity, and summed-score linking was applied to items selected for the Mini-PANSS. Results The majority of items forming the Positive and Negative subscales (i.e. 19 items) performed very well and discriminate better along symptom severity compared to the General Psychopathology subscale. Six of the seven Positive Symptom items, six of the seven Negative Symptom items, and seven out of the 16 General Psychopathology items were retained for inclusion in the Mini-PANSS. Summed score linking and linear interpolation was able to produce a translation table for comparing total subscale scores of the Mini-PANSS to total subscale scores on the original PANSS. Results show scores on the subscales of the Mini-PANSS can be linked to scores on the original PANSS subscales, with very little bias. Conclusions The study demonstrated the utility of non-parametric IRT in examining the item properties of the PANSS and to allow selection of items for an abbreviated PANSS scale. The comparisons between the 30-item PANSS and the Mini-PANSS revealed that the shorter version is comparable to the 30-item PANSS, but when applying IRT, the Mini-PANSS is also a good indicator of illness severity. PMID:22087503

Validation of self-directed learning instrument and establishment of normative data for nursing students in taiwan: using polytomous item response theory.

PubMed

Cheng, Su-Fen; Lee-Hsieh, Jane; Turton, Michael A; Lin, Kuan-Chia

2014-06-01

Little research has investigated the establishment of norms for nursing students' self-directed learning (SDL) ability, recognized as an important capability for professional nurses. An item response theory (IRT) approach was used to establish norms for SDL abilities valid for the different nursing programs in Taiwan. The purposes of this study were (a) to use IRT with a graded response model to reexamine the SDL instrument, or the SDLI, originally developed by this research team using confirmatory factor analysis and (b) to establish SDL ability norms for the four different nursing education programs in Taiwan. Stratified random sampling with probability proportional to size was used. A minimum of 15% of students from the four different nursing education degree programs across Taiwan was selected. A total of 7,879 nursing students from 13 schools were recruited. The research instrument was the 20-item SDLI developed by Cheng, Kuo, Lin, and Lee-Hsieh (2010). IRT with the graded response model was used with a two-parameter logistic model (discrimination and difficulty) for the data analysis, calculated using MULTILOG. Norms were established using percentile rank. Analysis of item information and test information functions revealed that 18 items exhibited very high discrimination and two items had high discrimination. The test information function was higher in this range of scores, indicating greater precision in the estimate of nursing student SDL. Reliability fell between .80 and .94 for each domain and the SDLI as a whole. The total information function shows that the SDLI is appropriate for all nursing students, except for the top 2.5%. SDL ability norms were established for each nursing education program and for the nation as a whole. IRT is shown to be a potent and useful methodology for scale evaluation. The norms for SDL established in this research will provide practical standards for nursing educators and students in Taiwan.

Iron allocation in leaves of Fe-deficient cucumber plants fed with natural Fe complexes.

PubMed

Zanin, Laura; Tomasi, Nicola; Rizzardo, Cecilia; Gottardi, Stefano; Terzano, Roberto; Alfeld, Matthias; Janssens, Koen; De Nobili, Maria; Mimmo, Tanja; Cesco, Stefano

2015-05-01

Iron (Fe) sources available for plants in the rhizospheric solution are mainly a mixture of complexes between Fe and organic ligands, including phytosiderophores (PS) and water-extractable humic substances (WEHS). In comparison with the other Fe sources, Fe-WEHS are more efficiently used by plants, and experimental evidences show that Fe translocation contributes to this better response. On the other hand, very little is known on the mechanisms involved in Fe allocation in leaves. In this work, physiological and molecular processes involved in Fe distribution in leaves of Fe-deficient Cucumis sativus supplied with Fe-PS or Fe-WEHS up to 5 days were studied combining different techniques, such as radiochemical experiments, synchrotron micro X-ray fluorescence, real-time reverse transcription polymerase chain reaction and in situ hybridization. In Fe-WEHS-fed plants, Fe was rapidly (1 day) allocated into the leaf veins, and after 5 days, Fe was completely transferred into interveinal cells; moreover, the amount of accumulated Fe was much higher than with Fe-PS. This redistribution in Fe-WEHS plants was associated with an upregulation of genes encoding a ferric(III) -chelate reductase (FRO), a Fe(2+) transporter (IRT1) and a natural resistance-associated macrophage protein (NRAMP). The localization of FRO and IRT1 transcripts next to the midveins, beside that of NRAMP in the interveinal area, may suggest a rapid and efficient response induced by the presence of Fe-WEHS in the extra-radical solution for the allocation in leaves of high amounts of Fe. In conclusion, Fe is more efficiently used when chelated to WEHS than PS and seems to involve Fe distribution and gene regulation of Fe acquisition mechanisms operating in leaves. © 2014 Scandinavian Plant Physiology Society.

Metabolic changes of iron uptake in N(2)-fixing common bean nodules during iron deficiency.

PubMed

Slatni, Tarek; Vigani, Gianpiero; Salah, Imen Ben; Kouas, Saber; Dell'Orto, Marta; Gouia, Houda; Zocchi, Graziano; Abdelly, Chedly

2011-08-01

Iron is an important nutrient in N(2)-fixing legume nodules. The demand for this micronutrient increases during the symbiosis establishment, where the metal is utilized for the synthesis of various iron-containing proteins in both the plant and the bacteroid. Unfortunately, in spite of its importance, iron is poorly available to plant uptake since its solubility is very low when in its oxidized form Fe(III). In the present study, the effect of iron deficiency on the activity of some proteins involved in Strategy I response, such as Fe-chelate reductase (FC-R), H(+)-ATPase, and phosphoenolpyruvate carboxylase (PEPC) and the protein level of iron regulated transporter (IRT1) and H(+)-ATPase proteins has been investigated in both roots and nodules of a tolerant (Flamingo) and a susceptible (Coco blanc) cultivar of common bean plants. The main results of this study show that the symbiotic tolerance of Flamingo can be ascribed to a greater increase in the FC-R and H(+)-ATPase activities in both roots and nodules, leading to a more efficient Fe supply to nodulating tissues. The strong increase in PEPC activity and organic acid content, in the Flamingo root nodules, suggests that under iron deficiency nodules can modify their metabolism in order to sustain those activities necessary to acquire Fe directly from the soil solution. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Helping Children Understand Disabilities.

ERIC Educational Resources Information Center

Zakariya, Sally Banks

1978-01-01

The program described uses simulation activities; exposure to aids and appliances; guest speakers; books, movies, slides, and videotapes; and class discussion to help elementary students understand disabilities. (IRT)

Icing Simulation Research Supporting the Ice-Accretion Testing of Large-Scale Swept-Wing Models

NASA Technical Reports Server (NTRS)

Yadlin, Yoram; Monnig, Jaime T.; Malone, Adam M.; Paul, Bernard P.

2018-01-01

The work summarized in this report is a continuation of NASA's Large-Scale, Swept-Wing Test Articles Fabrication; Research and Test Support for NASA IRT contract (NNC10BA05 -NNC14TA36T) performed by Boeing under the NASA Research and Technology for Aerospace Propulsion Systems (RTAPS) contract. In the study conducted under RTAPS, a series of icing tests in the Icing Research Tunnel (IRT) have been conducted to characterize ice formations on large-scale swept wings representative of modern commercial transport airplanes. The outcome of that campaign was a large database of ice-accretion geometries that can be used for subsequent aerodynamic evaluation in other experimental facilities and for validation of ice-accretion prediction codes.

Strategy, Distinctive Competence, and Organizational Performance.

ERIC Educational Resources Information Center

Snow, Charles C.; Hrebiniak, Lawrence G.

1980-01-01

Focuses on the perceptions of top managers in four industries (plastics, semiconductors, automotives, and air transportation) who examined relationships among strategy, distinctive competence, and organizational performance. (Author/IRT)

National Strategies for Technological Innovation

ERIC Educational Resources Information Center

Rossini, Frederick; Bozeman, Barry

1977-01-01

Considers the implications of the technological innovation literature for possible national strategies for innovation. Sketches highly generalized innovation strategies for nations at various levels of technological development. (Author/IRT)

A versatile Multisite Gateway-compatible promoter and transgenic line collection for cell type-specific functional genomics in Arabidopsis

PubMed Central

Platre, Matthieu Pierre; Barberon, Marie; Caillieux, Erwann; Colot, Vincent

2016-01-01

Summary Multicellular organisms are composed of many cell types that acquire their specific fate through a precisely controlled pattern of gene expression in time and space dictated in part by cell type-specific promoter activity. Understanding the contribution of highly specialized cell types in the development of a whole organism requires the ability to isolate or analyze different cell types separately. We have characterized and validated a large collection of root cell type-specific promoters and have generated cell type-specific marker lines. These benchmarked promoters can be readily used to evaluate cell type-specific complementation of mutant phenotypes, or to knockdown gene expression using targeted expression of artificial miRNA. We also generated vectors and characterized transgenic lines for cell type-specific induction of gene expression and cell type-specific isolation of nuclei for RNA and chromatin profiling. Vectors and seeds from transgenic Arabidopsis plants will be freely available, and will promote rapid progress in cell type-specific functional genomics. We demonstrate the power of this promoter set for analysis of complex biological processes by investigating the contribution of root cell types in the IRT1-dependent root iron uptake. Our findings revealed the complex spatial expression pattern of IRT1 in both root epidermis and phloem companion cells and the requirement for IRT1 to be expressed in both cell types for proper iron homeostasis. PMID:26662936

MHD Instabilities and Toroidal Field Effects on Plasma Column Behavior in Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khorshid, Pejman; Plasma Physics Research Center, Islamic Azad University, 14665-678, Tehran; Wang, L.

2006-12-04

In the edge plasma of the CT-6B and IRAN-T1 tokamaks the shape of plasma column based on MHD behavior has been studied. The bulk of plasma behavior during plasma column rotation as non-rigid body plasma has been investigated. We found that mode number and rotation frequency of plasma column are different in angle position, so that the mode number detected from Mirnov coils array located in poloidal angle on the inner side of chamber is more than outer side which it can be because of toroidal magnetic field effects. The results of IR-T1 and CT-6B tokamaks compared with each other,more » so that in the CT-6B because of its coils number must be less, but because of its Iron core the effect of toroidal magnetic field became more effective with respect to IR-T1. In addition, it is shown that the plasma column behaves as non-Rigid body plasma so that the poloidal rotation velocity variation in CT-6B is more than IR-T1. A relative correction for island rotation frequency has been suggested in connection with IRAN-T1 and CT-6B tokamak results, which can be considered for optical measurement purposes and also for future advanced tokamak control design.« less

Perfluorochemical (PFC) exposure in children: associations with impaired response inhibition.

PubMed

Gump, Brooks B; Wu, Qian; Dumas, Amy K; Kannan, Kurunthachalam

2011-10-01

Perfluorinated chemicals (PFCs) have been used widely in consumer products since the 1950s and are currently found at detectable levels in the blood of humans and animals across the globe. In stark contrast to this widespread exposure to PFCs, there is relatively little research on potential adverse health effects of exposure to these chemicals. We performed this cross-sectional study to determine if specific blood PFC levels are associated with impaired response inhibition in children. Blood levels of 11 PFCs were measured in children (N = 83) and 6 PFCs: perfluorooctane sulfonate (PFOS), perfluorohexane sulfate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctanesulfonamide (PFOSA), and perfluorodecanoic acid (PFDA) - were found at detectable levels in most children (87.5% or greater had detectable levels). These levels were analyzed in relation to the differential reinforcement of low rates of responding (DRL) task. This task rewards delays between responses (i.e., longer inter-response times; IRTs) and therefore constitutes a measure of response inhibition. Higher levels of blood PFOS, PFNA, PFDA, PFHxS, and PFOSA were associated with significantly shorter IRTs during the DRL task. The magnitude of these associations was such that IRTs during the task decreased by 29-34% for every 1 SD increase in the corresponding blood PFC. This study suggests an association between PFC exposure and children's impulsivity. Although intriguing, there is a need for further investigation and replication with a larger sample of children.

Experimental comparison of icing cloud instruments

NASA Technical Reports Server (NTRS)

Olsen, W.; Takeuchi, D. M.; Adams, K.

1983-01-01

Icing cloud instruments were tested in the spray cloud Icing Research Tunnel (IRT) in order to determine their relative accuracy and their limitations over a broad range of conditions. It was found that the average of the readings from each of the liquid water content (LWC) instruments tested agreed closely with each other and with the IRT calibration; but all have a data scatter (+ or - one standard deviation) of about + or - 20 percent. The effect of this + or - 20 percent uncertainty is probably acceptable in aero-penalty and deicer experiments. Existing laser spectrometers proved to be too inaccurate for LWC measurements. The error due to water runoff was the same for all ice accretion LWC instruments. Any given laser spectrometer proved to be highly repeatable in its indications of volume median drop size (DVM), LWC and drop size distribution. However, there was a significant disagreement between different spectrometers of the same model, even after careful standard calibration and data analysis. The scatter about the mean of the DVM data from five Axial Scattering Spectrometer Probes was + or - 20 percent (+ or - one standard deviation) and the average was 20 percent higher than the old IRT calibration. The + or - 20 percent uncertainty in DVM can cause an unacceptable variation in the drag coefficient of an airfoil with ice; however, the variation in a deicer performance test may be acceptable.

Retrieval dynamics in self-terminated memory search.

PubMed

Hussey, Erika K; Dougherty, Michael R; Harbison, J Isaiah; Davelaar, Eddy J

2014-02-01

Most free-recall experiments employ a paradigm in which participants are given a preset amount of time to retrieve items from a list. While much has been learned using this paradigm, it ignores an important component of many real-world retrieval tasks: the decision to terminate memory search. The present study examines the temporal characteristics underlying memory search by comparing within subjects a standard retrieval paradigm with a finite, preset amount of time (closed interval) to a design that allows participants to terminate memory search on their own (open interval). Calling on the results of several presented simulations, we anticipated that the threshold for number of retrieval failures varied as a function of the nature of the recall paradigm, such that open intervals should result in lower thresholds than closed intervals. Moreover, this effect was expected to manifest in interretrieval times (IRTs). Although retrieval-interval type did not significantly impact the number of items recalled or error rates, IRTs were sensitive to the manipulation. Specifically, the final IRTs in the closed-interval paradigm were longer than those of the open-interval paradigm. This pattern suggests that providing participants with a preset retrieval interval not only masks an important component of the retrieval process (the memory search termination decision), but also alters temporal retrieval dynamics. Task demands may compel people to strategically control aspects of their retrieval by implementing different stopping rules.

The Mayor's Influence in Urban School Desegregation

ERIC Educational Resources Information Center

Dunaway, David King; Beckum, Leonard Charles

1977-01-01

There are five primary areas in which mayors exert visible and invisible influence--appointments, decision-making, public statements, coordination of resources, and provision of basic services. (Author/IRT)

Low Cost Benefit Suggestions.

ERIC Educational Resources Information Center

Doyel, Hoyt W.; McMillan, John D.

1980-01-01

Outlines eight low-cost employee benefits and summarizes their relative advantages. The eight include a stock ownership program, a sick leave pool, flexible working hours, production incentives, and group purchase plans. (IRT)

Self-Concept Development in Young Children

ERIC Educational Resources Information Center

Stenner, A. Jackson; Katzenmeyer, William G.

1976-01-01

Contrary to most theories, the child's concept of self crystalizes during the early school years, during which period a massive process of psychological and social maturation takes place. (Author/IRT)

Alternative Reagans.

ERIC Educational Resources Information Center

Van Til, William

1981-01-01

In anticipating what educators might expect from President Reagan, the author examines the positions Reagan has taken as a practical politician, as a right winger, as a presidential candidate, and as a moderate. (IRT)

Raman scattering of IrTe2

NASA Astrophysics Data System (ADS)

Lee, Alexander; Thorsmolle, Verner; Artyukhin, Sergey; Yang, Jun; Cheong, Sang-Wook; Blumberg, Girsh

2014-03-01

IrTe2 presents a layered compound with a triangular lattice. It is known to exhibit a first order structural phase transition at approximately 260 K which is of a first order, corresponding to a formation of a superstructure with a period of five unit cells. Using polarized Raman spectroscopy we have studied the temperature dependence of 14 observed Raman allowed phononic modes. These phonons couple strongly to this transition and one additional first order transition at approximately 170 K. In the high-temperature phase only 3 modes are observed, while below approximately 280 K all 14 modes become visible. Below approximately 170 K only 11 modes are observed. Our results shed light on the possible mechanism driving the transitions. ACL, VKT and GB acknowledge support by NSF DMR-1104884.

Structure of chaotic magnetic field lines in IR-T1 tokamak due to ergodic magnetic limiter

NASA Astrophysics Data System (ADS)

Ahmadi, S.; Salar Elahi, A.; Ghorannevis, M.

2018-03-01

In this paper we have studied an Ergodic Magnetic Limiter (EML) based chaotic magnetic field for transport control in the edge plasma of IR-T1 tokamak. The resonance created by the EML causes perturbation of the equilibrium field line in tokamak and as a result, the field lines are chaotic in the vicinity of the dimerized island chains. Transport barriers are formed in the chaotic field line and actually observe in tokamak with reverse magnetic shear. We used area-preserving non-twist (and twist) Poincaré maps to describe the formation of transport barriers, which are actually features of Hamiltonian systems. This transport barrier is useful in reducing radial diffusion of the field line and thus improving the plasma confinement.

β-Lactamases in amoxicillin-clavulanate-resistant Escherichia coli strains isolated from a Chinese tertiary hospital.

PubMed

Ding, Juanjuan; Ma, Xitao; Chen, Zhuochang; Feng, Keqing

2013-08-01

A total of 52 strains were resistant to amoxicillin-clavulanate by disk diffusion method in a Chinese tertiary hospital from July 2011 to December 2011. Among these isolates, 2 isolates possessed a phenotype consistent with production of inhibitor-resistant temoniera (TEM) (IRT) β-lactamase, and the TEM-type gene was cloned into strains of Escherichia coli JM109 cells. Both had no blaTEM mutations and were identified as TEM-1 β-lactamase producers. As a result, no IRT β-lactamase was detected. Multiplex PCR detected most of these strains produced TEM-1 enzymes, and plasmid-mediated AmpC β-lactamase and oxacillinase-1 β-lactamases are important mechanisms of resistance as well. Copyright © 2013 Elsevier Inc. All rights reserved.

Transient analysis for the tajoura critical facility with IRT-2M HEU fuel and IRT-4M leu fuel : ANL independent verification results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garner, P. L.; Hanan, N. A.

2005-12-02

Calculations have been performed for postulated transients in the Critical Facility at the Tajoura Nuclear Research Center (TNRC) in Libya. These calculations have been performed at the request of staff of the Renewable Energy and Water Desalinization Research Center (REWDRC) who are performing similar calculations. The transients considered were established during a working meeting between ANL and REWDRC staff on October 1-2, 2005 and subsequent email correspondence. Calculations were performed for the current high-enriched uranium (HEU) core and the proposed low-enriched uranium (LEU) core. These calculations have been performed independently from those being performed by REWDRC and serve as onemore » step in the verification process.« less

CF and School

MedlinePlus

... Testing for Cystic Fibrosis CFTR-Related Metabolic Syndrome (CRMS) How Babies Are Screened in IRT-Only vs. ... Guidelines Infant Care Clinical Care Guidelines Management of CRMS in First 2 Years and Beyond Clinical Care ...

About Cystic Fibrosis

MedlinePlus

... Testing for Cystic Fibrosis CFTR-Related Metabolic Syndrome (CRMS) How Babies Are Screened in IRT-Only vs. ... Guidelines Infant Care Clinical Care Guidelines Management of CRMS in First 2 Years and Beyond Clinical Care ...

Allergic Bronchopulmonary Aspergillosis

MedlinePlus

... Testing for Cystic Fibrosis CFTR-Related Metabolic Syndrome (CRMS) How Babies Are Screened in IRT-Only vs. ... Guidelines Infant Care Clinical Care Guidelines Management of CRMS in First 2 Years and Beyond Clinical Care ...

Measuring the Financial Impact of Employee Attitudes

ERIC Educational Resources Information Center

Mirvis, Philip H.; Lawler, Edward E., III

1977-01-01

Results show expected direct-cost savings in absenteeism, turnover, and performance from an increase in job satisfaction. Saving associated with enhanced job involvement and motivation are also reported. (Author/IRT)

Impact of the Minimum Wage on Compression.

ERIC Educational Resources Information Center

Wolfe, Michael N.; Candland, Charles W.

1979-01-01

Assesses the impact of increases in the minimum wage on salary schedules, provides guidelines for creating a philosophy to deal with the impact, and outlines options and presents recommendations. (IRT)