bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SENSITIVITY OF PARAMETER ESTIMATES TO THE LATENT ABILITY DISTRIBUTION
Authors: Xu Xueli , Jia Yue
Published: August 2014

Estimation of item response model parameters and ability distribution parameters has been, and will remain, an important topic in the educational testing field. Much research has been dedicated to addressing this task. Some studies have focused on item parameter estimation when the latent ability was assumed to follow a normal distribution, whereas others have utilized nonparametric or semiparametric techniques to substitute the normal ability assumption. However, both approaches have their limitations. A normal ability assumption is not flexible enough to reflect possible deviations from symmetry, whereas the nonparametric and semiparametric techniques used to capture possible nonnormal features of the latent ability have difficulty in reaching satisfactory estimates for certain quantities of the ability distribution such as quantiles. Hence a continuous generalized skew normal (GSN) distribution was applied in this study to better capture the possible underlying asymmetric ability distribution. In addition, simultaneous estimation of both the item parameters and the distributional parameters was employed. The performance of the GSN was compared with the normal ability assumption in terms of item parameter and distributional parameter recoveries, based on a series of simulation studies. The results showed that (a) under the Rasch model, both the item parameter estimates and the distributional parameter estimates are robust to the misspecification of the ability distribution, and (b) under the two‐parameter logistic model, although the distributional parameter estimates are fairly robust, the item parameter estimates are slightly more sensitive to the misspecification of the ability distribution, especially when the underlying ability distribution is highly skewed.
A GENERAL PROCEDURE TO ASSESS THE INTERNAL STRUCTURE OF A NONCOGNITIVE MEASURE—THE STUDENT360 INSIGHT PROGRAM (S360) TIME MANAGEMENT SCALE
Authors: Ling Guangming , Rijmen Frank
Published: August 2014

The factorial structure of the Time Management (TM) scale of the Student 360: Insight Program (S360) was evaluated based on a national sample. A general procedure with a variety of methods was introduced and implemented, including the computation of descriptive statistics, exploratory factor analysis (EFA), and confirmatory factor analysis (CFA). Overall, the results indicated that the TM scale measured multidimensional constructs of TM with 5 factors. The paper concludes with a discussion of several issues concerning the wording of items and residual dependencies, as well as future directions for research.
HOW DOES THE KNOWLEDGE OF SUBGROUP MEMBERSHIP OF EXAMINEES AFFECT THE PREDICTION OF TRUE SUBSCORES?
Authors: Haberman Shelby J. , Sinharay Sandip
Published: August 2014

Subscores are reported for several operational assessments. Haberman (2008) suggested a method based on classical test theory to determine if the true subscore is predicted better by the corresponding subscore or the total score. Researchers are often interested in learning how different subgroups perform on subtests. Stricker (1993) and Livingston and Rupp (2004) found that the mean difference between the subgroups was not the same for the different subscores. We suggest new methods to investigate whether the quality of prediction of the true subscore improves if the investigator knows about the subgroup membership. We applied our suggested method to data from 4 operational testing programs. We found that the quality of prediction of the true subscore does not improve if the investigator knows the subgroup membership. We also found that whether the subscores have value added does not depend on the subgroups.
EVALUATION OF THE E‐RATER® SCORING ENGINE FOR THE GRE® ISSUE AND ARGUMENT PROMPTS
Authors: Ramineni Chaitanya , Trapani Catherine S. , Williamson David M. , Davey Tim , Bridgeman Brent
Published: August 2014

Automated scoring models for the e‐rater® scoring engine were built and evaluated for the GRE® argument and issue‐writing tasks. Prompt‐specific, generic, and generic with prompt‐specific intercept scoring models were built and evaluation statistics such as weighted kappas, Pearson correlations, standardized difference in mean scores, and correlations with external measures were examined to evaluate the e‐rater model performance against human scores. Performance was also evaluated across different demographic subgroups. Additional analyses were performed to establish appropriate agreement thresholds between human and e‐rater scores for unusual essays and the impact of using e‐rater on operational scores. The generic e‐rater scoring model with operational prompt‐specific intercept for the issue‐writing task and prompt‐specific e‐rater scoring model for the argument writing task were recommended for operational use. The two automated scoring models were implemented to produce check scores at a discrepancy threshold of 0.5 with human scores.
EFFECTIVE PRACTICES FOR DEVELOPING THE LITERACY SKILLS OF ENGLISH LANGUAGE LEARNERS IN THE ENGLISH LANGUAGE ARTS CLASSROOM
Authors: Turkan Sultan , Bicknell Jerome , Croft Andrew
Published: August 2014

This paper is a review of literature presenting instructional strategies—based on normative as well as empirical arguments—which have proven to be effective in envisioning whatallteachers need to know and be able to do to teach English language arts (ELA) to English language learners (ELLs). The studies selected for review address what is particular to teaching ELA to ELLs. The paper is divided into two main sections: (a) teachers' linguistic practices and (b) teachers' pedagogical practices. In the first section, we report on the studies that analyze teachers' understanding of linguistics and present implications for their instruction of ELLs. Three areas of effective practice are emphasized based on the particular aspects of teaching ELA to ELLs. The first area is that teachers should recognize that literacy skills in ELLs' native languages might influence the ways in which ELLs process linguistic information in English. The second area highlights the argument that teachers should find ways to facilitate ELLs' mastery of academic vocabulary. The third area covers the significance of enhancing ELLs' metacognitive reading skills. In the second section, on teacher pedagogical practices, we discuss two broad pedagogical skills that emerge from both the normative and empirical studies reviewed and are closely related: (a) the teachers' ability to help ELLs construct meaning from the texts or speech represented in the ELA classroom and (b) the teachers' ability to engage ELLs in actively learning to read and write. The paper ends with a summary and a brief reflective statement on the limitations of the review of the literature.
EXAMINING THE IMPACT OF DRIFTED POLYTOMOUS ANCHOR ITEMS ON TEST CHARACTERISTIC CURVE (TCC) LINKING AND IRT TRUE SCORE EQUATING
Authors: Li Yanmei
Published: August 2014

In a common‐item (anchor) equating design, the common items should be evaluated for item parameter drift. Drifted items are often removed. For a test that contains mostly dichotomous items and only a small number of polytomous items, removing some drifted polytomous anchor items may result in anchor sets that no longer resemble mini‐versions of the new and old test forms. In this study, the impact of drifted polytomous anchor items on the test characteristic curve (TCC) linking and item response theory (IRT) true score equating for a test containing only a small number of polytomous items was investigated. Simulated tests were constructed to mimic a real large‐scale test. The magnitude of the item parameter drift, anchor length, number of drifted polytomous items in the anchor set, and the ability distributions of the groups taking the old form and new form were manipulated. Results suggest that anchor length and number of drifted polytomous items had a relatively large impact on the linking and equating results. The accuracy of linking and equating results were affected by the magnitude of item parameter drift. The ability distributions of the groups had little effect on the linking and equating results. In general, excluding drifted polytomous anchor items resulted in an improvement in equating results.
A NOTE ON EXPLAINING AWAY AND PARADOXICAL RESULTS IN MULTIDIMENSIONAL ITEM RESPONSE THEORY
Authors: van Rijn Peter W. , Rijmen Frank
Published: August 2014

Hooker and colleagues addressed a paradoxical situation that can arise in the application of multidimensional item response theory (MIRT) models to educational test data. We demonstrate that this MIRT paradox is an instance of the explaining‐away phenomenon in Bayesian networks, and we attempt to enhance the understanding of MIRT models by placing the paradox in a broader statistical modeling perspective.
WHAT CAN REPEATED CROSS‐SECTIONAL STUDIES TELL US ABOUT STUDENT GROWTH?
Authors: Almond Russell G. , Sinharay Sandip
Published: August 2014

To answer questions about how students' proficiencies are changing over time, educational researchers are looking for data sources that span many years. Clearly, for answering questions about student growth, a longitudinal study—in which a single sample is followed over many years—is preferable to repeated cross‐sectional samples—in which a separate sample is taken every year. Repeated cross‐sectional studies, such as the National Assessment of Educational Progress (NAEP), however, are often readily available. Repeated cross‐sectional studies conflate several sources of variability (differences in the initial status of individuals, individual differences in the growth curves, and individual‐by‐measurement‐occasion differences) in ways that are not easily separated. Although repeated cross‐sectional studies can provide information about the growth of the averages, the growth of the averages corresponds to the average of the growth curves only in very restricted circumstances. This paper reviews the literature on modeling growth with an eye to characterizing the limitations of repeated cross‐sectional studies and understanding the sensitivity of the results to key decisions (particularly, choices of cut points). In most cases, repeated cross‐sectional studies should be used to confirm and contextualize the results of more targeted longitudinal studies.
TOPICAL TRENDS IN A CORPUS OF PERSUASIVE WRITING
Authors: Heilman Michael , Madnani Nitin
Published: August 2014

Many writing assessments use generic prompts about social issues. However, we currently lack an understanding of how test takers respond to such prompts. In the absence of such an understanding, automated scoring systems may not be as reliable as they could be and may worsen over time. To move toward a deeper understanding of responses to generic issue prompts, we analyzed topical trends in test takers' responses and correlated these trends with those found in the news. We found evidence that many trends are similar across essays and the news. However, we also observed some interesting differences. Based on these analyses, we make recommendations in this paper for developers of writing assessments and automated scoring systems.
STATISTICAL REPORT OF 2011 CBAL™ MULTISTATE ADMINISTRATION OF READING AND WRITING TESTS
Authors: Fu Jianbin , Wise Maxwell
Published: August 2014

In the Cognitively Based Assessment of, for, and as Learning (CBAL™) research initiative, innovative K‐12 prototype tests based on cognitive competency models are developed. This report presents the statistical results of the 2 CBAL Grade 8 writing tests and 2 Grade 7 reading tests administered to students in 20 states in spring 2011. Specifically, classical item statistics including rater reliabilities for human‐scored items, item p+ values, item‐total correlations, item response times, item omit and not‐reached rates, system error rates, differential item functioning, interscore correlations, and reliabilities of subscores and total scores are reported. In addition, t‐tests, multiple comparisons, correlations, and mixed models are used to examine the factors influencing test scores, including test form, test order, and various background variables at the student, teacher, and school levels. The results show that these 4 tests performed reasonably well.
EXPLORING ALTERNATIVE TEST FORM LINKING DESIGNS WITH MODIFIED EQUATING SAMPLE SIZE AND ANCHOR TEST LENGTH
Authors: Wang Lin , Qian Jiahe , Lee Yi‐Hsuan
Published: August 2014

The purpose of this study was to evaluate the combined effects of reduced equating sample size and shortened anchor test length on item response theory (IRT)‐based linking and equating results. Data from two independent operational forms of a large‐scale testing program were used to establish the baseline results for evaluating the results from two alternative designs. Under the two alternative designs, two simulated conditions were created from the original data. Under one condition, we reduced the equating sample size (from about 2,000 to about 1,000) per anchor item and shortened the anchor test length (by half) per equating sample. Under the other condition, we reduced the sample size (from about 2,000 to about 1,000) per anchor item only. A complete grouped jackknife replication method was used to estimate the standard errors of the linking and equating procedures from 100 jackknife replicate samples; the complete procedures included IRT calibrations, item parameter scaling, and IRT true score equating. The findings from a comparison of the results from the two simulated conditions and the baseline results showed that neither alternative design had any practical impact on the linking and equating results for either test form.
A CRITERION TO EVALUATE THE INDIVIDUAL RAW‐TO‐SCALE EQUATING CONVERSIONS
Authors: Guo Hongwen , Puhan Gautam , Walker Michael
Published: August 2014

In this study we investigated when an equating conversion line is problematic in terms of gaps and clumps. We suggest using the conditional standard error of measurement (CSEM) to measure the scale scores that are inappropriate in the overall raw‐to‐scale transformation.
DIMENSIONALITY ANALYSIS OF CBAL™ WRITING TESTS
Authors: Fu Jianbin , Chung Seunghee , Wise Maxwell
Published: August 2014

The Cognitively Based Assessment of, for, and as Learning (CBAL™) research initiative is aimed at developing an innovative approach to K‐12 assessment based on cognitive competency models. Because the choice of scoring and equating approaches depends on test dimensionality, the dimensional structure of CBAL tests must be understood. The purpose of this study was to investigate the dimensionality of 4 CBAL Grade 8 writing tests. Each of the 4 tests focused on one of the following writing genres: persuasive letter/memorandum, research‐based report (pamphlet), persuasive essay, and literature essay. Dimensionality was investigated using exploratory and confirmatory factor analyses. The results show multidimensionality and support subscore structures and bifactor task models for all 4 tests.
POSTSTRATIFICATION EQUATING BASED ON TRUE ANCHOR SCORES AND ITS RELATIONSHIP TO LEVINE OBSERVED SCORE EQUATING
Authors: Chen Haiwen (Henry) , Livingston Samuel A.
Published: August 2014

This paper presents a new equating method for the nonequivalent groups with anchor test design: poststratification equating based on true anchor scores. The linear version of this method is shown to be equivalent, under certain conditions, to Levine observed score equating, in the same way that the linear version of poststratification equating is equivalent to Tucker equating. Some issues related to this result are discussed.
AN INVESTIGATION OF THE EFFICACY OF CRITERION REFINEMENT PROCEDURES IN MANTEL‐HAENSZEL DIF ANALYSIS
Authors: Zwick Rebecca , Ye Lei , Isham Steven
Published: August 2014

Differential item functioning (DIF) analysis is a key component in the evaluation of the fairness and validity of educational tests. Although it is often assumed that refinement of the matching criterion always provides more accurate DIF results, the actual situation proves to be more complex. To explore the effectiveness of refinement, we conducted a simulation study consisting of 40 conditions that varied in terms of amount and pattern of DIF, sample sizes, and ability distributions. We found that the effectiveness of refinement was heavily dependent on whether DIF was balanced (with positive DIF values compensating for negative DIF values) or unbalanced (all in one direction). In balanced conditions, the unrefined method generally produced better results, whereas, in unbalanced conditions, the opposite was true. In the absence of information about the pattern of DIF, it is probably best to choose the refined method because it is only slightly disadvantageous in balanced conditions, whereas the unrefined method can be substantially disadvantageous in certain unbalanced conditions.
TOEFL11: A CORPUS OF NON‐NATIVE ENGLISH
Authors: Blanchard Daniel , Tetreault Joel , Higgins Derrick , Cahill Aoife , Chodorow Martin
Published: August 2014

This report presents work on the development of a new corpus of non‐native English writing. It will be useful for the task of native language identification, as well as grammatical error detection and correction, and automatic essay scoring. In this report, the corpus is described in detail.
ITEM RESPONSE THEORY
Authors: Carlson James E. , von Davier Matthias
Published: August 2014

Few would doubt that ETS researchers have contributed more to the general topic of item response theory (IRT) than individuals from any other institution. In this report, we briefly review most of those contributions, dividing them into sections by decades of publication, beginning with early work by Fred Lord and Bert Green in the 1950s and ending with recent work that produced models involving complex structures and multiple dimensions.
A CBAL™ SCIENCE MODEL OF COGNITION: DEVELOPING A COMPETENCY MODEL AND LEARNING PROGRESSIONS TO SUPPORT ASSESSMENT DEVELOPMENT
Authors: Liu Lei , Rogat Aaron , Bertling Maria
Published: August 2014

The purpose of this report is to describe a science competency model and 3 related learning progressions, which were developed by applying the CBAL™ approach (Bennett & Gitomer, 2009) to the domain of middle school science. The Cognitively Based Assessment of, for, and as Learning (CBAL) science competency model and its related learning progressions were developed by reviewing existing literature on learning sciences and science education, which have placed increasing emphasis on learners' knowledge and ability to apply scientific knowledge to conduct evidence‐based reasoning. In this report, we present the 5 competencies in our science competency model that reflect current efforts in the Next Generation Science Standards and the recent reform‐based curriculum to promote integrated and generative understanding. In addition, we report 3 hypothesized learning progressions related to our competency model to define the increasing sophistication of both content understanding and the capacity to carry out scientific inquiry. Then we discuss features of assessment prototypes developed under the guidance of the competency model and the learning progressions, by illustrating parts of 1 sample formative assessment task prototype.
INVESTIGATING TEN‐YEAR TRENDS OF LEARNING OUTCOMES AT COMMUNITY COLLEGES
Authors: Liu Ou Lydia , Roohr Katrina Crotts
Published: August 2014

Community colleges currently enroll about 44% of the undergraduate students in the United States and are rapidly expanding. It is of critical importance to obtain direct evidence of student learning to see if students receive adequate training at community colleges. This study investigated the 10‐year trends of community college students' (n = 46,403) performance in reading, writing, mathematics, and critical thinking, as assessed by the ETS® Proficiency Profile (EPP), an assessment of college‐level learning outcomes. Results showed that community college students caught up with and significantly outperformed students from liberal arts colleges by the end of the 10‐year period and made significant improvement in critical‐thinking skills. An increasing gender gap was observed in mathematics at community colleges. Prevalent ethnic minority and English as a second language (ESL) gaps were noted but gaps between ESL and non‐ESL students and between Hispanic and White students were decreasing. Additionally, Asian students at community colleges showed an overall decline in performance. Findings from this study provide significant implications for community college leaders, researchers, and policymakers.
WEIGHTING TEST SAMPLES IN IRT LINKING AND EQUATING: TOWARD AN IMPROVED SAMPLING DESIGN FOR COMPLEX EQUATING
Authors: Qian Jiahe , Jiang Yanming , von Davier Alina A.
Published: August 2014

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 samples of examinees so that the IRT linking and equating can be more precise at an administration level as well as over a large number of administrations? This is a question of optimal sampling design in linking and equating. To obtain an improved sampling design for invariant linking and equating across testing administrations, we applied weighting techniques to yield a weighted sample distribution that is consistent with the target population distribution. The goal is to obtain a stable Stocking‐Lord test characteristic curve (TCC) linking and a true‐score equating that is invariant across administrations. To study the weighting effects on linking, we first selected multiple subsamples from a data set. We then compared the linking parameters from subsamples with those from the data and examined whether the linking parameters from the weighted sample yielded smaller mean square errors (MSE) than those from the unweighted subsample. To study the weighting effects on true‐score equating, we also compared the distributions of the equated scores. Generally, the findings were that the weighting produced good results.
REPURPOSING A BUSINESS LEARNING OUTCOMES ASSESSMENT TO COLLEGE STUDENTS OUTSIDE OF THE UNITED STATES: VALIDITY AND RELIABILITY EVIDENCE
Authors: Ling Guangming
Published: August 2014

One concern when repurposing a test to a new population is whether the test is measuring the same construct in a valid and reliable way that is comparable to the intended population. Following the guidelines of the International Test Commission and the ETS Standards for Quality and Fairness, this study was designed to collect evidence in support of repurposing the Major Field Test for the Bachelor's Degree in Business (MFT‐B) for use in undergraduate level business programs outside of the United States. The author examined the test's reliability and internal structure based on 930 senior college students from 9 business programs in Asia, Europe, the Middle East, and South America. Each participating institution satisfied 2 requirements for this study: (a) having a bachelor's level business curriculum that is similar to their U.S. peer programs and (b) using English as the instructional language. The analyses of the data showed that the MFT‐B has the same factor structure for the non‐U.S.–based sample as that for their U.S. peers. In addition, the test scores for the non‐U.S.–based sample are highly reliable (.90) overall, with some variations among the 9 programs. Both types of evidence support the notion that the MFT‐B is appropriate when repurposed for use with non‐U.S.–based business programs.
Association between combative behavior requiring intervention and delirium in hospitalized patients
Authors: Uldall Karina , Williams Barbara L. , Dunn Jessica D. , Blackmore C. Craig
Published: August 2014

BACKGROUND

We hypothesized that delirium contributes to combative behavior requiring intervention in hospitalized patients. Delirium identification would therefore potentially provide an opportunity for prevention and early identification of patients at risk, thereby improving safety for patients and staff.

OBJECTIVE

To determine whether delirium is associated with combative behavior requiring intervention in a general hospital population.

DESIGN

Case control study.

SETTING

A 336‐bed, nonuniversity, teaching hospital serving adults in the Pacific Northwest.

PATIENTS

One hundred twenty consecutive hospitalized patients with combative behavior requiring intervention compared to 159 randomly selected inpatient control subjects, all from 2011.

INTERVENTION

Bivariate statistics were used to compare demographics; diagnoses; presence of delirium, dementia, substance use, other psychiatric diagnosis; medications; hospital length of stay; and discharge disposition. We used stepwise logistic regression to determine the association of combative behavior requiring intervention with delirium after adjustment for covariates.

RESULTS

Delirium preceding the combative behavior was present in 50% (60/120) of patients with combative behavior requiring intervention compared to 16% (26/159) of controls (P < 0.001). Combative‐behavior patients were hospitalized longer (9.4 vs 4.5 days, P < 0.001), and were more likely to be discharged to a skilled nursing facility (26%, 31/120) or to leave against medical advice (10%, 12/120, P < 0.001). Delirium was strongly associated with combative behavior requiring intervention, after adjustment (odds ratio: 3.8, 95% confidence interval: 2.0–7.3, P < 0.001).

CONCLUSION

Delirium is strongly associated with combative behavior requiring intervention, which poses a significant safety risk for patients and staff. Journal of Hospital Medicine 2014;9:658–662. © 2014 Society of Hospital Medicine
Re‐evaluation of the Roseau Tuff eruptive sequence and other ignimbrites in Dominica, Lesser Antilles
Authors: HOWE TRACY M. , LINDSAY JAN M. , SHANE PHIL , SCHMITT AXEL K. , STOCKLI DANIEL F.
Published: August 2014

The island of Dominica hosts several ignimbrites, including the Roseau Tuff, thought to represent the largest eruption in the Caribbean in the past 200 000 years. The volcanic stratigraphy of the island is poorly understood due to limited outcrops and a paucity of geochemical and geochronological data. The discovery of a new fully accessible exposure of three ignimbrites intercalated with paleosols provides an opportunity to re‐evaluate the current stratigraphic framework of ignimbrite‐forming eruptions on the island. Whole‐rock analyses of pumice clasts from Dominica ignimbrites are andesitic (61–66% SiO2) and in most cases are geochemically indistinguishable. Ignimbrites in the north of the island have less evolved glass compositions (73–75% SiO2) and more mafic orthopyroxene compositions (En > 56) than their southern counterparts (75–78% SiO2; En < 56). Pumice clasts from ignimbrites in southern Dominica have indistinguishable groundmass glass and mineral chemistry, making correlation of these deposits difficult. New (U–Th)/He eruption ages for the southern ignimbrites indicate that at least six separate explosive eruptions occurred between 24 and 61 ka. The non‐unique geochemistry of these deposits, together with the new (U−Th)/He ages, suggests that the large volume inferred for the Roseau Tuff eruption may actually be a composite of six smaller, geochemically homogeneous eruptions.
Pretransplant Diagnosis of Hepatocellular Carcinoma by Gadoxetic Acid–Enhanced and Diffusion-Weighted Magnetic Resonance Imaging
Authors: Hwang Jiyoung , Kim Young Kon , Kim Jong Man , Lee Won Jae , Choi Dongil , Hong Seong Sook
Published: August 2014

We sought to evaluate the diagnostic performance of gadoxetic acid–enhanced magnetic resonance imaging (MRI) with and without additional diffusion-weighted imaging (DWI) in the detection of hepatocellular carcinoma (HCC) in pretransplant patients. We included 63 liver transplant patients (54 men and 9 women; mean age = 52 years) who had undergone gadoxetic acid–enhanced MRI with DWI at 3.0 T within 90 days before transplantation. Two image sets were reviewed for HCC in 2 separate sessions by 2 independent observers: the gadoxetic acid set and the combined set (gadoxetic acid plus DWI). The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for each image set. In all, 113 HCCs (size range = 0.5–7.8 cm, mean = 2.0 ± 1.3 cm) were identified in the 52 liver explants. The per-lesion sensitivity of the combined set (78.8% for both observers) was higher than the sensitivity of the gadoxetic acid set [71.7% (P = 0.02) and 72.6% (P = 0.03) for the 2 observers], with the highest trend for Child-Pugh class A (94.4% and 97.2% for gadoxetic acid and 97.2% for combined), which was followed by class B (73.2% for gadoxetic acid and 82.9% for combined) and then class C (47.2% for gadoxetic acid and 55.6% for combined, P = 0.01). The per-patient negative predictive value of the combined set was higher than that of the gadoxetic acid set for both observers (P = 0.046). There was no difference in specificity between the 2 image sets (P > 0.05). The addition of DWI to gadoxetic acid–enhanced MRI resulted in significantly higher sensitivity to detect HCC. However, the sensitivity decreased with increasing cirrhosis severity for both imaging types. Liver Transpl 20:1436–1446, 2014. © 2014 AASLD.
Histidine kinases mediate differentiation, stress response, and pathogenicity inMagnaporthe oryzae
Authors: Jacob Stefan , Foster Andrew J. , Yemelin Alexander , Thines Eckhard
Published: August 2014

The aim of this study is a functional characterization of 10 putative histidine kinases (HIKs)‐encoding genes in the phytopathogenic fungusMagnaporthe oryzae. TwoHIKs were found to be required for pathogenicity in the fungus. It was found that the mutant strainsΔMohik5andΔMohik8show abnormal conidial morphology and furthermoreΔMohik5is unable to form appressoria. BothHIKs MoHik5p and MoHik8p appear to be essential for pathogenicity since the mutants fail to infect rice plants. MoSln1p and MoHik1p were previously reported to be components of theHOGpathway inM. oryzae. TheΔMosln1mutant is more susceptible to salt stress compared toΔMohik1, whereasΔMohik1appears to be stronger affected by osmotic or sugar stress. In contrast to yeast, theHOGsignaling cascade in phytopathogenic fungi apparently comprises more elements. Furthermore, vegetative growth of the mutantsΔMohik5andΔMohik9was found to be sensitive to hypoxia‐inducing NaNO2‐treatment. Additionally, it was monitored that NaNO2‐treatment resulted in MoHog1p phosphorylation. As a consequence we assume a first simplified model for hypoxia signaling inM. oryzaeincluding theHOGpathway and theHIKs MoHik5p and MoHik9p.
Experimental validation of the hyperpolarized 129Xe chemical shift saturation recovery technique in healthy volunteers and subjects with interstitial lung disease
Authors: Stewart Neil J. , Leung General , Norquay Graham , Marshall Helen , Parra‐Robles Juan , Murphy Philip S. , Schulte Rolf F. , Elliot Charlie , Condliffe Robin , Griffiths Paul D. , Kiely David G. , Whyte Moira K. , Wolber Jan , Wild Jim M.
Published: August 2014

Purpose

To assess the sensitivity of the hyperpolarized 129Xe chemical shift saturation recovery (CSSR) technique for noninvasive quantification of changes to lung microstructure and function in idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc).

Methods

Ten healthy volunteers, four subjects with SSc and four with IPF were scanned at 1.5 T. A CSSR pulse sequence was implemented using binomial‐composite radiofrequency pulses to monitor 129Xe magnetization in tissues and blood plasma (T/P) and red blood cells (RBCs). The dynamics of 129Xe uptake into these compartments were fitted with three existing analytical models of gas diffusion to extract parameters of lung physiology. These parameters were quantitatively compared between models.

Results

Uptake of xenon into the pulmonary capillaries was impaired in subjects with IPF and SSc. Statistically significant septal thickening was measured by 129Xe CSSR in IPF patients. Preliminary data suggests age‐dependent alterations to septal thickness in healthy volunteers. These findings were reproduced using each of the literature models. CSSR‐derived parameters were compared with gold‐standard indicators of pulmonary function; diffusing capacity of carbon monoxide and pulmonary transit‐time.

Conclusions

CSSR with hyperpolarized 129Xe is sensitive to pathology‐induced degradation of lung structure/function and shows promise for quantification of disease severity and monitoring treatment response. Magn Reson Med 74:196–207, 2015. © 2014 Wiley Periodicals, Inc.
A home‐built digital optical MRI console using high‐speed serial links
Authors: Tang Weinan , Wang Weimin , Liu Wentao , Ma Yajun , Tang Xin , Xiao Liang , Gao Jia‐Hong
Published: August 2014

Purpose

To develop a high performance, cost‐effective digital optical console for scalable multichannel MRI.

Methods

The console system was implemented with flexibility and efficiency based on a modular architecture with distributed pulse sequencers. High‐speed serial links were optimally utilized to interconnect the system, providing fast digital communication with a multi‐gigabit data rate. The conventional analog radio frequency (RF) chain was replaced with a digital RF manipulation. The acquisition electronics were designed in close proximity to RF coils and preamplifiers, using a digital optical link to transmit the MR signal.

Results

A prototype of the console was constructed with a broad frequency range from direct current to 100 MHz. A temporal resolution of 1 μs was achieved for both the RF and gradient operations. The MR signal was digitized in the scanner room with an overall dynamic range between 16 and 24 bits and was transmitted to a master controller over a duplex optic fiber with a high data rate of 3.125 gigabits per second. High‐quality phantom and human images were obtained using the prototype on both 0.36T and 1.5T clinical MRI scanners.

Conclusion

A homemade digital optical MRI console with high‐speed serial interconnection has been developed to better serve imaging research and clinical applications. Magn Reson Med 74:578–588, 2015. © 2014 Wiley Periodicals, Inc.
Study of mechanical, thermal, morphological, and process rheology of acrylonitrile styrene acrylate (ASA)/ Na+1 poly(ethylene‐co‐methacrylic acid) ionomer blend
Authors: Datta Pulak , Guha Chandan , Sarkhel Gautam
Published: August 2014

Acrylonitrile–styrene–acrylic (ASA) terpolymer was blended with a sodium neutralized poly (ethylene‐co‐methacrylic acid) ionomer to develop a weather‐resistant ASA with good heat sealing and adhesion properties. Both tensile strengths and modulus were reduced by about 45% with an increase in Na‐ionomer concentration of 50%. The mechanical data were fitted with different models that predict mechanical behavior. The thermal stability was increased with the incorporation of ionomer. The temperature corresponding to 50% mass loss (Tm50) was increased from 400°C (for ASA) to 427°C for 50/50 ASA/Na‐ionomer blend. SEM and AFM micrographs reveal the cone‐shaped microstructure on the ASA matrix surface after a critical Na‐ionomer concentration of 30%. This blend system follows typical non‐Newtonian behavior. The heat sealing performance study with metal was also carried out to investigate the utilization of these blend systems as a protective layer for metal. POLYM. ENG. SCI., 55:1571–1579, 2015. © 2014 Society of Plastics Engineers
Proteomics and circadian rhythms: It's all about signaling!
Authors: Mauvoisin Daniel , Dayon Loïc , Gachon Frédéric , Kussmann Martin
Published: August 2014

Proteomic technologies using MS offer new perspectives in circadian biology, in particular the possibility to study PTMs. To date, only very few studies have been carried out to decipher the rhythmicity of protein expression in mammals with large‐scale proteomics. Although signaling has been shown to be of high relevance, comprehensive characterization studies of PTMs are even more rare. This review aims at describing the actual landscape of circadian proteomics and the opportunities and challenges appearing on the horizon. Emphasis was given to signaling processes for their role in metabolic health as regulated by circadian clocks and environmental factors. Those signaling processes are expected to be better and more deeply characterized in the coming years with proteomics.
Depletion of superjunction power MOSFETs visualized by electron beam induced current and voltage contrast measurements
Authors: Kirnstoetter Stefan , Faccinelli Martin , Jelinek Moriz , Schustereder Werner , Laven Johannes G. , Schulze Hans‐Joachim , Hadley Peter
Published: August 2014

Electron Beam Induced Current (EBIC) measurements were used to produce cross sectional images of superjunction power transistors. These images show how the depletion width expands under reverse bias. Superjunctions are alternating p‐ and n‐type doped vertical columns placed between drain and source in a power transistor (Deboy et al., in: Proc. IEDM, 983–685 (1998); Lorenz et al., in: Proc. PCIM Europe, 250–258 (1998)). These columns allow a higher substrate doping of the drift region, resulting in a lower on‐state resistance while still maintaining a high breakdown voltage. When the device is reverse biased, the space charge region of the superjunction should expand symmetrically due to the homogeneous doping (in the n and p region) until the complete device depletes. The depletion process was also visualized using voltage contrast (VC) measurements. Here the secondary electron signal was detected when the device was reverse biased. We show that EBIC and VC measurements can provide valuable input for process tuning and process simulations, enabling the use of smaller dimensions and higher doping levels
Temperature dependent switching behaviour of nickel silicided undoped silicon nanowire devices
Authors: Beister Jürgen , Wachowiak Andre , Heinzig André , Trommer Jens , Mikolajick Thomas , Weber Walter M.
Published: August 2014

In this work, we investigate the temperature dependence of electrical switching properties of back‐gated, undoped Si‐nanowire field‐effect transistors with Ni‐silicided source/drain contacts. A simple, phenomenological model illustrates the leading order temperature dependence of the source‐drain current, which originates predominantly from charge carrier injection by tunneling through the Schottky junction. Drain current versus gate voltage measurements have been performed for various temperatures and several drain voltages on a single nanowire device. The temperature dependence of the drain‐source current for specific gate and drain voltages is analysed within the framework of voltage dependent effective barrier heights. As a result, the temperature dependence of the tunnelling current is not only important for the sub‐threshold region, but also plays a significant role in the transistor “on‐state”. In addition, the effective barrier heights for electrons and holes tend towards the natural Schottky barriers of the NiSi2‐Si interface, if the applied external fields generate the case of flat band condition at the injection Schottky barrier, i.e. in the deep “off‐state” region. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Performance of Phase I Dispersion Control Charts for Process Monitoring
Authors: Abbasi Saddam Akber , Riaz Muhammad , Miller Arden , Ahmad Shabbir
Published: August 2014

Control charts are usually implemented in two phases: the retrospective phase (phase I) and the monitoring phase (phase II). The performance of any phase II control chart structure depends on the preciseness of the control limits obtained from the phase I analysis. In statistical process control, the performance of phase I dispersion charts has mainly been investigated for normal or contaminated normal distributions of the quality characteristic of interest. Little work has been carried out to investigate the performance of a wide range of possible phase I dispersion charts for processes following non‐normal distributions. The current study deals with the proper choice of a control chart for the evaluation of process dispersion in phase I. We have analyzed the performance of a wide range of dispersion control charts, including two distribution‐free structures. The performance of the control charts is evaluated in terms of probability to signal, under normal and non‐normal process setups. These results will be useful for quality control practitioners in their selection of a phase I control chart. Copyright © 2014 John Wiley & Sons, Ltd.
Combating phishing attacks via brand identity and authorization features
Authors: Geng Guang‐Gang , Lee Xiao‐Dong , Zhang Yan‐Ming
Published: August 2014

Phishing, also called brand spoofing, has become the most troubling scam on the Internet, which seriously threatens the Web security. The essence of phish is that “robbers” use false sites, which look like a trustworthy brand site, where favicon, logo and copyright notice are important brand identities. We analyzed 78‐day phishing data of PhishTank and Anti‐Phishing Working Group (APWG). The statistics show that more than 98.93% phishing sites contain at least one brand entity—favicon, logo or copyright notice. Indeed, only a few lowest‐quality phishing campaigns do not use such brand elements. Obviously, brand entities are powerful weapons of phishers to trick users. By analyzing the characteristics of brand entities in phishing sites, several brand identity features are extracted. However, only brand entities do not consider whether the Web page with brand entities belongs to the corresponding brand or has an authorization to use the brand entities. To solve this problem, redirection, incoming links and Domain Name System (DNS) information‐based brand authorization features are further extracted to discriminate the sites with branding rights from phishing sites. Based on extracted features, statistical anti‐phishing classification models are trained. We collected a diverse spectrum of corpora containing 3863 phishing cases from PhishTank and APWG, and 17 571 legitimate samples from DMOZ, Google and DNS resolution log. Experimental evaluations show that the model achieves 98.8% true positive rate and 0.09% false positive rate, which demonstrates the competitive performances of extracted features for statistical anti‐phishing in practice. Copyright © 2014 John Wiley & Sons, Ltd.
Multi‐source broadcast authentication with Combined Key Chains for wireless ad hoc networks
Authors: Choi Seonho , Sun Kun , Eom Hyeonsang , Jung Edward
Published: August 2014

Multiple trust sources may be needed for broadcast in wireless ad hoc networks. For example, multiple base stations may be employed in some wireless sensor networks, or multiple trusts may be distributed among multiple routing nodes in multi‐hop routing protocol. Most of the previously proposed multicast/broadcast authentication protocols assume a single source of trust. With multiple trust sources, it becomes difficult to design resource‐efficient authentication protocols for multicast/broadcast services. Simply extending traditional approaches will result in increased bandwidth and memory consumptions in proportion to the number of trust sources.

In this paper, we propose a new scheme utilizing Combined Key Chains. If there are m trust sources, our scheme generates m + 1 key chains, where m of them are distributed among the m source nodes and the last one is used as a Verification Key Chain in all the receiver nodes. The communication overhead is small and constant, and the memory requirement at a verifier node is also minimal. Copyright © 2014 John Wiley & Sons, Ltd.
The elemental distribution in the oxide scale on a conventionally cast and a metallurgical ODS FeCrAl alloy characterized by ToF‐SIMS
Authors: Malmberg Per , Hellström Kristina
Published: August 2014

The commercial FeCrAl alloys Kanthal APMTTM (powder metallurgical) and Kanthal AFTM (conventionally cast) contain reactive elements (RE) to improve scale properties. These alloys were oxidized at 1100 °C for 168 h to form a protective alumina scale. These scales were then investigated with Time of flight secondary ion mass spectrometry to examine the distribution of the REs. The results showed an accumulation of Y, Zr, Mg and Mo in the outermost part of the oxide scales on both alloys. Low levels of these elements were also detected in the oxide scales. In addition, Mo was accumulated together with Cr in the oxide of APMT. Copyright © 2014 John Wiley & Sons, Ltd.
XAFS and XPS study of hydro‐/dehydrogenation reaction of Mg–Pd nanoparticles
Authors: Ogawa Satoshi , Fujimoto Taishi , Mizutani Tsuyoshi , Ogawa Masahiro , Yogi Chihiro , Kato Kazuo , Ohta Toshiaki , Yoshida Tomoko , Yagi Shinya
Published: August 2014

The nanoparticles composed of Mg and Pd atoms (Mg–Pd NPs) have been fabricated by the gas evaporation method, and the variation of the chemical state during hydro‐/dehydrogenations has been investigated by X‐ray photoelectron spectroscopy (XPS) and in‐situ X‐ray absorption fine structure (XAFS) analyses. Both XPS and XAFS spectra have indicated that the Mg–Pd NPs contain the chemical state of the metallic Pd and Mg–Pd alloy phases. The Mg–Pd alloy phase has been identified as MgPd and Mg6Pd by the Pd K‐edge EXAFS analysis. The hydrogen release of the Mg–Pd NPs has not been observed after first hydrogenation due to the migration of Mg toward the surface of the Mg–Pd NPs during the hydrogen storage. This irreversible migration has led the inhibition of the hydrogen diffusion into the surface from the inside of the Mg–Pd NPs. Copyright © 2014 John Wiley & Sons, Ltd.
Robust Microcapsules with Controlled Permeability from Silk Fibroin Reinforced with Graphene Oxide
Authors: Ye Chunhong , Combs Zachary A. , Calabrese Rossella , Dai Hongqi , Kaplan David L. , Tsukruk Vladimir V.
Published: August 2014

Robust and stable microcapsules are assembled from poly‐amino acid‐modified silk fibroin reinforced with graphene oxide flakes using layer‐by‐layer (LbL) assembly, based on biocompatible natural protein and carbon nanosheets. The composite microcapsules are extremely stable in acidic (pH 2.0) and basic (pH 11.5) conditions, accompanied with pH‐triggered permeability, which facilitates the controllable encapsulation and release of macromolecules. Furthermore, the graphene oxide incorporated into ultrathin LbL shells induces greatly reinforced mechanical properties, with an elastic modulus which is two orders of magnitude higher than the typical values of original silk LbL shells and shows a significant, three‐fold reduction in pore size. Such strong nanocomposite microcapsules can provide solid protection of encapsulated cargo under harsh conditions, indicating a promising candidate with controllable loading/unloading for drug delivery, reinforcement, and bioengineering applications.