bluuebunny/crossref_metadata_2025 huggingface dataset:
COLLEGE BOARD COMPUTERIZED PLACEMENT TESTS
Authors: Ward William C. , Kline Roberta G. , Flaugher Jan
Published: September 2014

Seventeen two‐ and four‐year institutions participated in pilot testing of the College Board Computerized Placement Tests during 1984 and 1985. Data were available for over 2,500 students who took one or more modules of the adaptive test; participating institutions planned to test at least 2,000 more by the end of 1985. In most institutions examinees were volunteers currently enrolled in English, reading, or mathematics courses.

Students taking part in the 1984 pilot completed a questionnaire describing their reactions, and many took a short paper and pencil test for comparison with the computerized tests. In both years of pilot activity, students' grades in relevant courses and their scores on other tests used for placement were obtained.

Reactions of students and of faculty and staff were very favorable. Both groups found the computer easy to use; both liked especially the adaptation of the test to a student's level of skills and the ability to obtain immediate score reports.

Analyses of the relations between test scores and end‐of‐term grades were done separately by level of course (developmental or introductory college‐level). Grades in single courses constitute a very fallible criterion, confounded by a number of factors. Nonetheless, moderate correlations with grades, with median values generally in the range from .30 to .40, were found for all categories of courses examined except for developmental mathematics courses; in the latter, the median correlations were over .50. These coefficients are similar in magnitude to those found in studies with professionally constructed paper and pencil test batteries.

A few samples provided data appropriate for a comparison of relations to grades for sex and ethnic subgroups. There was no evidence of differential prediction for these groups, but, with small sample sizes and volunteer examinees, these results are far from definitive.

No specific contrasts can be made of relations to grades of the computerized tests and other placement tests given to pilot examinees; in most instances the other tests available were institution‐specific, and the sample sizes were too small to permit confident generalizations about differences in the relations. Over all samples and courses for which data are available, the computerized test scores showed higher correlations with grades than did scores from paper and pencil tests in 59% of the possible contrasts.
GRE VERBAL ANALOGY ITEMS: EXAMINEE REASONING ON ITEMS
Authors: Duran Richard P. , Enright Mary K. , Peirce Leslie P.
Published: September 2014

Information about how GRE examinees solve verbal analogy problems was obtained in this study through protocol analysis. High‐ and low‐ability subjects who had recently taken the GRE General Test were asked to “think aloud” as they worked through eight analogy items. These items varied factorially on the dimensions of vocabulary difficulty (easy vs. difficult), relationship difficulty (easy vs. difficult), and stem‐key correspondence (independent vs. overlapping). A scoring system was developed that included three phases: (i) a cognitive process analysis, (ii) a global description of the subjects' strategies, and (iii) an evaluation of their performance. Overall we found that vocabulary and correspondence tended to have multiple effects on how subjects solved analogies and affected whether they solved them correctly. On the other hand, relationship difficulty tended to affect whether or not subjects achieved correct solutions but not how they attained solutions. As expected, high‐ability subjects tended to use higher‐level or more sophisticated strategies more often than low‐ability subjects. However, the use of higher‐level strategies was common for both groups of subjects. The results are compared with those reported in the cognitive science literature. In addition, the implication of these results for test development and the usefulness of the protocol methodology are discussed.
ISSUES IN RACE/ETHNICITY IDENTIFICATION PROCEDURES IN THE NATIONAL ASSESSMENT OF EDUCATIONAL PROGRESS, PART I: A COMPARISON OF OBSERVER REPORTS AND SELF‐IDENTIFICATION
Authors: Rivera Charlene , Pennock‐Roman Maria
Published: September 2014

In this investigation, the validity of observer reports versus student self‐reports of race and ethnicity in the National Assessment of Educational Progress (NAEP) for ages 9, 13, and 17 were evaluated. Data from seven surveys (1975‐1984) were analyzed, with sample sizes ranging from 15,859 to 38,899. While the concordance between the two methods for both White and Black students was very high (95% or better), the two classifications gave very disparate results for the other four racial/ethnic groups. For example, observers undercounted self‐identified Hispanic 17–year‐olds by 25% to 48%. Language background was significantly (p < .0001) more consistent with self‐identification than with observer reports for 17‐year‐old Hispanic students which showed that self reports were more valid than observed ethnicity in this age group. However, the results for ages 9 and 13 were less clear‐cut. The implications of the findings for continuity in NAEP data sets and the validity of reported group achievement data for Hispanic students are discussed.
FACTORS AFFECTING DIFFERENTIAL ITEM FUNCTIONING FOR BLACK EXAMINEES ON SCHOLASTIC APTITUDE TEST ANALOGY ITEMS1
Authors: Schmitt Alicia P. , Bleistein Carole A.
Published: September 2014

The purpose of the present investigation was to identify item factors that may contribute to differential item functioning (DIF) for Black examinees on Scholastic Aptitude Test (SAT) analogy items. This research was considered necessary because analogy items have repeatedly been identified as differentially more difficult for Black examinees. The research was performed in two steps. Initially items in three forms were classified according to several possible explanatory factors. Preliminary analyses identified several factors that seemed to affect DIF for Black examinees. In order to confirm these hypothesized factors, a second step involved classifying and analyzing analogy items from two additional SAT forms.

The most significant finding is that Black students appear to need more time to complete the SAT verbal sections than White students with comparable total SAT verbal scores. This differential speededness effect makes analogy items appear differentially more difficult for Black examinees. Once differential item functioning statistics were corrected for speededness, a smaller number of analogy items were identified as differentially more difficult. In addition, evaluation of the hypothesized factors showed that some of the factors are interdependent and no clear distinction could be made to determine out their individual effects. These item factors are: item position within each analogy set, difficulty, subject matter content, and level of abstractness. The effects of homographs and semantic relationship types are also confounded with the previous factors. The only factor that seemed to be independent was “vertical relationships”. In general, a vertical or word associative answering strategy seems to be more consistently used by Black examinees on those items with negative DIF.

Generalizations to be drawn from these results are limited because the analyses are based on regular administration items which tend to have several factors operating in a single item and which contain infrequent occurrence of some factors. At this stage, these results provide a clearer picture of how comparable Black and White students respond on analogy items and the factors that might influence their performance.
EXPLOITING AUXILIARY INFORMATION ABOUT ITEMS IN THE ESTIMATION OF RASCH ITEM DIFFICULTY PARAMETERS
Authors: Mislevy Robert J.
Published: September 2014

Standard procedures for estimating the item parameters in IRT models make no use of auxiliary information about test items, such as their format or content, or the skills they require for solution. This paper describes a framework for exploiting this information, thereby enhancing the precision and stability of item parameter estimates and providing diagnostic information about items' operating characteristics. The principles are illustrated in a context for which a relatively simple approximation is available: empirical Bayes estimation of Rasch item difficulty parameters.
A COMPARISON OF STRATEGIES USED BY BLACK AND WHITE STUDENTS IN SOLVING SAT VERBAL ANALOGIES USING A THINKING ALOUD METHOD AND A MATCHED PERCENTAGE‐CORRECT DESIGN
Authors: Freedle Roy , Kostin Irene , Schwartz Laraine M.
Published: September 2014

Two studies are reported which investigate how Black and White examinees differ in their ability to solve analogy items. The first helps to identify three factors which affect differential ethnic performance on analogy items; the second study carried out a controlled experiment in order to investigate, via a thinking aloud paradigm, how the same three factors influenced the types of strategies that were differentially evoked for two matched groups of Black and White students.

In Study 1 three variables were found to be significantly associated with ethnic examinee differences in solving analogies: the item difficulty level (easy/hard dimension), whether the item had science content or not, and whether the item used a part/whole relationship in the stem. The conclusion reached in Study 1 was that Black examinees perform differentially better than the matched White examinees on the hard analogy items (typically these had a non‐science content), and appear to systematically perform less well vis‐a‐vis the matched White examinees on the easy analogy items (which often have a science content).

The results for Study 2 indicated that three strategies help to account for ethnic differences in solving analogy items:

use of an indirect or weak induction (used primarily by Black students on the hard science items; use of this strategy, especially for hard science items, helped Blacks to get more of these items correct).

use of word association in selecting a response which typically results in a wrong option being chosen (this was used more often by the Black students for all items except hard science items for which Black and White students were approximately equal in use of this strategy).

problems pronouncing the words in the item stem (Black students mispronounced some of the stem words significantly more often than White students).

Collectively these results helped to clarify some of the significant differences found between the two ethnic student groups in solving analogy items as a function of the item's characteristics. In general both studies provided evidence that item difficulty (the easy/hard dimension) was a significant factor underlying ethnic performance; the evidence showed that Black students perform better than their matched White student counterparts on the hard items and perform less well with respect to the easy items. But for Study 2 no confirming evidence was found that Black students performed less well on items involving science content, contrary to the results found in Study 1. Reasons for such differences across studies are discussed. Over and above ethnic differences, additional analyses in Study 2 uncovered differential strategy use as a function of whether analogy items contained a science or nonscience content.
TEN‐YEAR TRENDS IN SAT SCORES AND OTHER CHARACTERISTICS OF HIGH SCHOOL SENIORS TAKING THE SAT AND PLANNING TO STUDY MATHEMATICS, SCIENCE, OR ENGINEERING
Authors: Grandy Jerilee
Published: September 2014

This study analyzed data from the Scholastic Aptitude Test (SAT) taken by high school seniors between 1975 and 1986. Its purpose was to study trends in the numbers, test scores, and other characteristics of examinees planning to major in math, science, and engineering, and to compare these data with comparable data from examinees planning to major in other areas.

The major findings were as follows:

The number of examinees planning to major in math, science, and engineering increased until 1983 and has since declined. Aerospace and electrical engineering as well as international relations showed steadily increasing interest, while interest in majoring in computer science declined 49 percent in the past three years.

Examinees planning to major in math, science, and engineering in 1986 obtained SAT Verbal scores averaging 19 points higher than the average for all examinees, although the means varied greatly depending upon the specific major field choice.

The average SAT Mathematics scores of examinees planning to major in math, science, and engineering in 1986 were 38 points higher than the average for all test takers. There is considerable variation in the math aptitudes of examinees planning to study math, science, and engineering. The highest means have been obtained consistently by those planning to major in physics. Those planning to major in agriculture, child psychology, general psychology, social psychology, sociology, law enforcement, and miscellaneous social sciences all have had averages consistently below the mean for all examinees.

Examinees intending to study pre‐medicine, classics, comparative literature, philosophy, classical languages, Chinese, Latin, Russian, education of the gifted and talented, and mathematics education had higher means than those interested in math, science, and engineering.

The Verbal and Math scores of examinees interested in computer science have declined 26 and 40 points respectively in the last ten years.

There are still more males than females interested in math, science, and engineering, and the women do not seem to be catching up with the men in terms of majoring in these fields.

Women planning to major in electrical, mechanical, and civil engineering have higher average SAT Math scores than the men interested in these fields.

Mean SAT Math scores of blacks planning to major in math, science, and engineering have risen considerably over the past decade, especially among those planning to major in mathematics or statistics.
STRENGTH OF THE ANALYTICAL FACTOR OF THE GRE GENERAL TEST IN SEVERAL SUBGROUPS: A FULL‐INFORMATION FACTOR ANALYSIS APPROACH
Authors: Schaeffer Gary A. , Kingston Neal M.
Published: September 2014

This study examined the factor structure of the GRE General Test to appraise the extent to which an analytical factor could be identified that was distinguishable from verbal and quantitative factors. Full‐information factor analysis was employed in several groups of undergraduate majors on items from one edition of the GRE General Test. In general, three factors emerged for each group of undergraduate majors. Two of the factors were defined by verbal and quantitative items. A third factor typically had analytical reasoning items loading most heavily on it. No discernible pattern emerged regarding the relationships of the logical reasoning items and other items. The magnitudes of the intercorrelations among the verbal, quantitative, and analytical factors generally were similar across groups. Finally, the assessment of the differences among major groups was tentative and not well defined due to the extent of differences found among randomly equivalent groups of psychology majors.
THE RELATIONSHIP OF UNDERGRADUATE MAJOR TO GENERAL KNOWLEDGE SCORES
Authors: DeMauro Gerald E.
Published: September 2014

Scores from the October 1986 and March 1987 national administrations of the NTE Test of General Knowledge were analyzed to determine if area of undergraduate major was related to performance on the four sections of the test. To control for the range of skills associated with different reasons for taking the test, self‐reported cumulative undergraduate grade point average was used as a covariate in the analyses. Results for both administrations supported the construct validity of the test. The highest scores on the literature and fine arts sections were achieved by humanities majors, social science majors achieved the highest scores on the social studies section, and natural science (including math, physical science and geological science) majors achieved the highest scores on the math and science sections.
CAUSAL INFERENCE, PATH ANALYSIS AND RECURSIVE STRUCTURAL EQUATIONS MODELS
Authors: Holland Paul W.
Published: September 2014

Rubin's model for causal inference in experiments and observational studies is enlarged to analyze the problem of “causes causing causes” and is compared to path analysis and recursive structural equations models. A special quasi‐experimental design, the encouragement design, is used to give concreteness to the discussion by focusing on the simplest problem that involves both direct and indirect causation. Rubin's model is shown to extend easily to this situation and to specify conditions under which the parameters of path analysis and recursive structural equations models have causal interpretations.
SCALE DRIFT IN ON‐LINE CALIBRATION
Authors: Stocking Martha L.
Published: September 2014

Recent advances in psychometrics and computer technology encourage the development of model‐based methods of individualized testing on a microcomputer, where each examinee receives short tests and the number of pretest items that can be administered is severely restricted. On‐line (i.e., data is collected on operational equipment) methods for calibrating pretest items in this setting face new challenges. In the context of adaptive testing, two LOGIST‐based methods of on‐line calibration were developed and are described. These two methods are tried out and compared in a simulation study using data for the CAT‐ASVAB.
SOME CONSIDERATIONS IN MAINTAINING ADAPTIVE TEST ITEM POOLS
Authors: Stocking Martha L.
Published: September 2014

The construction of parallel editions of conventional tests for purposes of test security while maintaining score comparability has always been a recognized and difficult problem in psychometrics and test construction. The introduction of new modes of testing, e.g., adaptive testing, changes the nature of the problem but does not make it disappear. Items in adaptive test item pools may become overused and require replacement. However, in order to insure score comparability, important characteristics of the pool must remain constant. Three methods of selecting candidate new items and three methods of identifying items for replacement are developed and compared with each other and with a previous method through a simulation study.
SOME CONSEQUENCES OF THE UNCERTAINTY IN IRT LINKING PROCEDURES
Authors: Sheehan Kathleen M. , Mislevy Robert J.
Published: September 2014

In many practical applications of item response theory, the parameters of overlapping subsets of test items are estimated from different samples of examinees. A linking procedure is then employed to place the resulting item parameter estimates onto a common scale. It is standard practice to ignore the uncertainty associated with the linking step when drawing inferences that involve items from different subsets, a situation that arises, for example, in the measurement of change. This paper outlines how the uncertainty can be accounted for, and exemplifies the ideas with a jackknife approximation for the Stocking‐Lord linking procedure. Examples from the National Assessment of Educational Progress suggest that the resulting uncertainty will usually be negligible for inferences about individuals, but can constitute a major source of estimation error in aggregate statistics such as changes in group means.
A COMPARISON OF HISPANIC AND WHITE NON‐HISPANIC STUDENTS' OMIT PATTERNS ON THE SCHOLASTIC APTITUDE TEST1,2
Authors: Rivera Charlene , Schmitt Alicia P.
Published: September 2014

The standardization methodology was used to analyze omitted responses of Hispanic examinees on the Scholastic Aptitude Test. Results indicate that both Mexican‐Americans and Puerto Rican students omitted less than White students of comparable ability but that Mexicans Americans tended to omit even less. Examination of items with the least differential omit rate by both Hispanic groups indicate that items with true cognates or words with a common root in English and Spanish were omitted differentially less. Some dependency on ability level was observed for the omit patters of Puerto Rican examinees.
INFERRING EXAMINEE ABILITY WHEN SOME ITEM RESPONSES ARE MISSING
Authors: Mislevy Robert J. , Wu Pao‐Kuei
Published: September 2014

The basic equations of item response theory (IRT) provide a foundation for inferring examinees' abilities and items' operating characteristics from observed responses. In practice, though, examinees will usually not have provided a response to every available item–for reasons that may or may not have been intended by the test administrator, and that may or may not be related to examinee ability. The mechanisms that produce missingness must be taken into account if correct inferences are to be drawn. Using concepts introduced by Rubin (1976), we discuss the implications for ability and item parameter estimation that are entailed by alternate test forms, targeted testing, adaptive testing, time limits, and omitted responses.
THE ROLE OF COLLATERAL INFORMATION ABOUT EXAMINEES IN ITEM PARAMETER ESTIMATION
Authors: Mislevy Robert J. , Sheehan Kathleen M.
Published: September 2014

Standard procedures for estimating item parameters in item response theory (IRT) ignore collateral information that may be available about examinees, such as their standing on demographic and educational variables. This paper describes circumstances under which collateral information about examineesmaybe used to make inferences about item parameters more precise, and circumstances under which itmustbe used to obtain correct inferences.
DIAGNOSTIC ASSESSMENT IN INSTRUCTION
Authors: Forehand Garlie A. , Rice Myrtle W.
Published: September 2014

This paper describes an experimental program of interactive assessment and instruction called GUIDES to Learning and Instruction. The program was designed for instruction in college level remedial and developmental programs and has been experimentally implemented in four colleges. By the use of micro‐computer administration of measurement, the program provides sustained involvement in realistic tasks, uses a variety of response formats, including free response, probes for explanations of poor performance, gives feedback and second tries, and communicates to students and instructors. The paper discusses conclusions from implementation research regarding patterns of use, validity for instruction, and roles of instructors.
UNDERSTANDING DOCUMENT LITERACY: VARIABLES UNDERLYING THE PERFORMANCE OF YOUNG ADULTS
Authors: Kirsch Irwin S. , Mosenthal Peter B.
Published: September 2014

The purpose of this study was to identify a set of critical variables that underlie the performance of a national sample of young adults on a diverse set of document literacy tasks. The identification of these variables provides an important first step toward building a theoretical model that would systematically account for the constructs of document processing. With such a theoretical model, document designers and instructional‐program developers could use their understanding of document‐processing constructs in ways that could strategically address the production and processing of documents.

The sixty‐one tasks (and their associated documents) that make up the document scale of the NAEP Young Adult Literacy assessment were parsed using a specially devised grammar. Based upon the parsings, variables were identified to account for the probability of success for the total population and for major subgroups of interest. The variables identified accounted for 89 percent of the variance for the total population of young adults. Among racial/ethnic groups, these variables accounted for 89 percent of the variance for White, 81 percent for Black, and 87 percent for Hispanic young adults. Among levels of education, these variables accounted for 56 percent of the variance for young adults with 0–8 years of schooling, 81 percent for young adults with 9 to 12 years of schooling, 88 percent for young adults with high‐school degrees, and 84 percent for young adults with post‐high‐school degrees. The findings of this study are discussed in terms of the need to provide a more general framework for describing, comparing, and researching documents than has been the case in previous document studies.
CONFIDENCE BANDS FOR THE THREE‐PARAMETER LOGISTIC ITEM RESPONSE CURVE
Authors: Lord Frederic M. , Pashley Peter J.
Published: September 2014

A large sample method for obtaining asymptotic simultaneous confidence bands for a three‐parameter logistic response curve is described. A procedure is given which requires as input maximum likelihood parameter estimates and an asymptotic error covariance matrix. Illustrative plots of item response curves with corresponding confidence bands are presented.
DEVELOPING AND EVALUATING A MACHINE‐SCORABLE, CONSTRAINED CONSTRUCTED‐RESPONSE ITEM
Authors: Braun Henry I. , Bennett Randy Elliot , Frye Douglas , Soloway Elliot
Published: September 2014

The use of constructed response items in large scale standardized testing has been hampered by the costs and difficulties associated with obtaining reliable scores. The advent of expert systems may signal the eventual removal of this impediment. This study investigated the accuracy with which expert systems could score a new, non‐multiple choice item type. The item type presents a faulty solution to a computer programming problem and asks the student to correct the solution. This item type was administered to a sample of high school seniors enrolled in an Advanced Placement course in Computer Science who also took the Advanced Placement Computer Science (APCS) Test. Results indicated that the expert systems were able to produce scores for between 82% and 97% of the solutions encountered and to display high agreement with a human reader on which solutions were and were not correct. Diagnoses of the specific errors produced by students were less accurate. Correlations with scores on the objective and free‐response sections of the APCS examination were moderate. Implications for additional research and for testing practice are offered.
CONFIRMATORY ANALYSIS OF TEST STRUCTURE USING MULTIDIMENSIONAL ITEM RESPONSE THEORY
Authors: McKinley Robert
Published: September 2014

The purpose of this research was to develop and evaluate a confirmatory approach to assessing test structure using multidimensional item response theory (MIRT). The approach investigated involves adding to the exponent of the MIRT model an item structure matrix that allows the user to specify the ability dimensions measured by an item. Various combinations of item structures were fit to two sets of simulation data with known true structures, and the results were evaluated using a likelihood ratio chi‐square statistic and two information‐based model selection criteria. The results of these analyses support the use of the confirmatory MIRT approach, since it was found that the procedures could recover the true item structures. It was also found that adding an additional ability dimension that forces together items that ought not to be together noticeably deteriorates the quality of the solution. On the other hand, imposing structures different from, but not inconsistent with, the true structures does not necessarily yield worse fit. Finally, in terms of model fit statistics, the consistent Akaike information criterion performed better than the simple Akaike information criterion, while the likelihood ratio chi‐square was clearly inadequate.
THE RELATIONSHIP OF CONSTRAINED FREE‐RESPONSE TO MULTIPLE‐CHOICE AND OPEN‐ENDED ITEMS
Authors: Bennett Randy Elliot , Rock Donald A. , Braun Henry I. , Frye Douglas , Spohrer James C. , Soloway Elliot
Published: September 2014

This study examined the relationship of a machine‐scorable, constrained free‐response computer science item that required the student to debug a faulty program to two other types of items: (1) multiple‐choice and (2) free response requiring production of a computer program. Confirmatory factor analysis was used to test the fit of a three‐factor model to these data and to compare the fit of this model to three alternatives. These models were fit using two random‐half samples, one given a faulty program containing one bug and the other a program with three bugs. A single‐factor model best fit the data for the sample taking the 1‐bug constrained free response and a two‐factor model fit the data for the second sample. In addition, the factor intercorrelations showed this item type to be significantly related to both the free‐response items and the multiple‐choice measures.
JAMES‐STEIN ESTIMATION
Authors: Brandwein Ann Cohen , Strawderman William E.
Published: September 2014

This paper presents an expository development of James‐Stein estimation with substantial emphasis on exact results for non‐normal location models.

The themes of the paper are a) that the improvement possible over the best invariant estimator via shrinkage estimation is not surprising but expected from a variety of perspectives; b) that the amount of shrinkage allowable to preserve domination over the best invariant estimator, is, when properly interpreted, relatively free from the assumption of normality; and c) the potential savings in risk are substantial when accompanied by good quality prior information.
F33O4 Magnetic Nanoparticles for Cinnamic Acid Extraction from Ramulus Cinnamomi
Authors: Huang Xiu Xiang , Lu Jun Yu , Lai Hong Fang , Wei Lian Qiang
Published: September 2014

A facile solid‐phase extraction (SPE) method based on bare Fe3O4 magnetic nanoparticles (Fe3O4 NPs) was developed to capture cinnamic acid (CA) from a well‐known traditional Chinese medicine, Ramulus cinnamomi, for high performance liquid chromatography (HPLC) analysis. The as‐prepared Fe3O4 NPs were characterized via Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Several parameters that influence CA extraction rate, such as the amount of Fe3O4 NPs, shaking time, methanol content, eluent pH, and elution time, were investigated. The experimental results show that the CA extraction was 86.9 % at optimal condition, and the mass yield of CA extraction was found to be 0.00021 %. This study demonstrates that the developed CA extraction method is simple, cheap and environmentally friendly. Therefore, the proposed method has a potential for CA separation and purification from complex biological samples.
Mesoporous Silica MCM‐41 Supported N‐Heterocyclic Carbene‐Pd Complex for Heck and Sonogashira Coupling Reactions
Authors: Sarkar Shaheen M. , Yusoff Mashitah Mohd , Rahman Md. Lutfor
Published: September 2014

Heterocyclic carbene‐Pd complex was anchored onto the mesoporous silica MCM‐41 which exhibits high catalytic activity in Heck reaction under phosphine free reaction conditions for the reaction of iodo/bromoarenes with olefinic compounds such as butyl acrylate, isopropyl acrylate and styrene. This catalytic system also showed high activity for Sonogashira coupling reaction of various aryl halides under copper, phosphine and solvent‐free reaction conditions. The air and thermally stable catalyst were reused several times without significant loss of its activity. High efficiency of the catalyst along with its recycling ability and the rather low Pd‐loading demonstrated in both Heck and Sonogashira coupling reactions are the merits of the presented catalyst system.
Increasing root and leaf growth and yield in Mg‐deficient faba beans (Vicia faba) by MgSO4 foliar fertilization
Authors: Neuhaus Christina , Geilfus Christoph‐Martin , Mühling Karl‐Hermann
Published: September 2014

Magnesium (Mg) deficiency reduces yield and quality of crops as Mg is involved in carbohydrate and protein anabolism. Foliar application of MgSO4 represents a means of ameliorating the nutritional status of crops growing under conditions of deficiency. Foliar Mg application has been demonstrated to increase the chlorophyll concentration and vegetative yield of plants. However, in crop plants used for seed production, the limited number of available studies provides only conflicting results in terms of the efficiency of Mg leaf application on yield and quality. We have examined the effect of increasing Mg foliar application rates on differentially developed leaves and leaf stages with regards to Mg concentration, chlorophyll concentration and biomass formation. Our data reveal that in order to obtain significant effects MgSO4 concentrations in the spraying solution should be higher than 50 mM, as lower concentrations did not lead to significant changes in the vegetative or generative material. Positive effects of the foliar application on chlorophyll concentration and leaf area were only measured in leaves treated with 200 mM foliar MgSO4. The application of Mg did not affect the parameters chlorophyll, ion concentration and leaf area in the newly developing leaves, but it had an important influence with regard to yield traits, especially on the formation of pods. The quality of the seeds with regard to the protein concentration was reduced in response to the magnesium deficiency treatment, but the application of foliar magnesium prevented a significant loss of protein.
Quantifying moisture and roughness with Support Vector Machines improves spectroscopic soil organic carbon prediction
Authors: Römer Christoph , Rodionov Andrei , Behmann Jan , Pätzold Stefan , Welp Gerhard , Plümer Lutz
Published: September 2014

The challenges of Vis‐NIR spectroscopy are permanent soil surface variations of moisture and roughness. Both disturbance factors reduce the prediction accuracy of soil organic carbon (SOC) significantly. For improved SOC prediction, both disturbance effects have to be determined from Vis‐NIR spectra, which is especially challenging for roughness. Thus, an approach for roughness quantification under varying moisture and its impact on SOC assessment using Support Vector Machines is presented here.
A novel design of microstrip antenna with reconfigurable band rejection for cognitive radio applications
Authors: Ojaroudi N. , Ghadimi N. , Ojaroudi Y. , Ojaroudi S.
Published: September 2014

This article discusses the use of compact ultrawideband (UWB) microstrip monopole antenna with reconfigurable band rejection in cognitive radio. Frequency characteristics of the antenna can be reconfigured electronically to have a variable single band‐notched function to block interfering signals from 5 to 6 GHz wireless local area network (WLAN), 5.79–6.40 GHz intelligent transport system (ITS) and 8.02–8.4 GHz international telecommunication union (ITU). Using pairs of C‐shaped and L‐shaped parasitic structures in the ground plane, additional resonances are excited and hence much wider impedance bandwidth can be produced. Using these modified structures, the usable upper frequency of the antenna is extended from 10.4 to 14.5 GHz which provides a wide usable fractional bandwidth of more than 135%. To generate a reconfigurable band‐stop performance, we use three PIN diodes within the embedded structures in the ground plane. By changing the ON/OFF conditions of the PIN diodes, the antenna can be operated as UWB, and is reconfigurable in terms of the ability to selectively have band stops in the WLAN/ITS/ITU bands. The proposed monopole antenna has compact size with simple structure. Good VSWR and radiation pattern characteristics are obtained in the frequency band of interest. Experimental results show that the proposed antenna could be a good candidate for ultrawideband cognitive radio application. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2998–3003, 2014
Thermal conductivity of polypropylene composites with hybrid fillers of boron nitride and vapor‐grown carbon fiber
Authors: Cheewawuttipong Wattanaphon , Tanoue Shuichi , Uematsu Hideyuki , Iemoto Yoshiyuki
Published: September 2014

High thermal conductivity fillers of boron nitride (BN) and vapor‐grown carbon fiber (VGCF) were used alone or incorporate to prepare polypropylene (PP) composites. The effects of filler content, particle size and shape, and single vs. hybrid BN/VGCF fillers were investigated with respect to the thermal conductivity of the PP composites. The thermal conductivity of PP/BN composites depended upon the content and particle size of the BN. Increased content and length of VGCF had the effect of increasing the thermal conductivity of the PP composites. Hybrid fillers were created with a mixture of medium‐sized BN and long‐length VGCF; hybrid BN/VGCF fillers enhanced the thermal conductivity of PP composites with a lower total content compared with PP composites containing only medium‐sized BN particles. POLYM. COMPOS., 37:936–942, 2016. © 2014 Society of Plastics Engineers
Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers
Authors: Lee Chia‐Fen , Hsu Mei‐Ling , Chu Chun‐Hsun , Wu Tsung‐Yuan
Published: September 2014

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3441–3451
Stability Conditions and Interior Ballistics of Recoilless Projected Water Disruptor
Authors: Radomski Marek
Published: September 2014

The results of an analysis concerning the recoil effect as well as a mathematical model describing the internal ballistics of a two‐chambered projected water disruptor launcher are presented herein. Conditions for stability of the disruptor are formulated. The considerations are illustrated with example calculation results.
Sequence and conformational preferences at termini of α‐helices in membrane proteins: Role of the helix environment
Authors: Shelar Ashish , Bansal Manju
Published: September 2014

α‐helices are amongst the most common secondary structural elements seen in membrane proteins and are packed in the form of helix bundles. These α‐helices encounter varying external environments (hydrophobic, hydrophilic) that may influence the sequence preferences at their N and C‐termini. The role of the external environment in stabilization of the helix termini in membrane proteins is still unknown. Here we analyze α‐helices in a high‐resolution dataset of integral α‐helical membrane proteins and establish that their sequence and conformational preferences differ from those in globular proteins. We specifically examine these preferences at the N and C‐termini in helices initiating/terminating inside the membrane core as well as in linkers connecting these transmembrane helices. We find that the sequence preferences and structural motifs at capping (Ncap and Ccap) and near‐helical (N' and C') positions are influenced by a combination of features including the membrane environment and the innate helix initiation and termination property of residues forming structural motifs. We also find that a large number of helix termini which do not form any particular capping motif are stabilized by formation of hydrogen bonds and hydrophobic interactions contributed from the neighboring helices in the membrane protein. We further validate the sequence preferences obtained from our analysis with data from an ultradeep sequencing study that identifies evolutionarily conserved amino acids in the rat neurotensin receptor. The results from our analysis provide insights for the secondary structure prediction, modeling and design of membrane proteins. Proteins 2014; 82:3420–3436. © 2014 Wiley Periodicals, Inc.
AROME–NWC: a new nowcasting tool based on an operational mesoscale forecasting system
Authors: Auger Ludovic , Dupont Olivier , Hagelin Susanna , Brousseau Pierre , Brovelli Pascal
Published: September 2014

The AROME–NWC nowcasting system has been developed in order to cover the nowcasting 0–6 h range. It is based on the existing AROME mesoscale model, from which the lateral boundary conditions and the first‐guess file are taken. The difference between those two systems is basically the observation window length and a very short cut‐off time. Studies have been carried out to show that in practice it is not necessary to compute a set of background‐error statistics matrices as a function of the forecast lead time of the first‐guess file. The spin‐up of the system has been proven to be small and the 15 min cut‐off to be long enough to keep a good forecast quality. This nowcasting system has been validated against the operational mesoscale model AROME: it has been shown that it performs better for nowcasting ranges as regards temperature, humidity and wind, due to its use of more recent observations. The precipitation forecasts are less satisfactory, with some improvement during the day and some degradation at night.
Simulation of shallow‐water jets with a unified element‐based continuous/discontinuous Galerkin model with grid flexibility on the sphere
Authors: Marras S. , Kopera M. A. , Giraldo F. X.
Published: September 2014

We test the behaviour of a unified continuous/discontinuous Galerkin (CG/DG) shallow‐water model in spherical geometry with curved elements on three different grids of ubiquitous use in atmospheric modelling: (i) the cubed‐sphere, (ii) the reduced latitude–longitude, and (iii) the icosahedral grid. Both conforming and non‐conforming grids are adopted including static and dynamically adaptive grids for a total of twelve mesh configurations. The behaviour of CG and DG on the different grids are compared for a nonlinear midlatitude perturbed jet and for a linear case that admits an analytic solution. Because the inviscid solution on certain grids shows a high sensitivity to the resolution, the viscous counterpart of the governing equations is also solved and the results compared. The logically unstructured element‐based CG/DG model described in this article is flexible with respect to arbitrary grids. However, we were unable to define a best grid configuration that could possibly minimize the error regardless of the characteristic geometry of the flow. This is especially true if the governing equations are not regularized by the addition of a sufficiently large, fully artificial, diffusion mechanism, as will be shown. The main novelty of this study lies in the unified implementation of two element‐based Galerkin methods that share the same numerical machinery and do not rely on any specific grid configuration to solve the shallow‐water equation on the sphere.
The algebraic diagrammatic construction scheme for the polarization propagator for the calculation of excited states
Authors: Dreuw Andreas , Wormit Michael
Published: September 2014

The algebraic diagrammatic construction (ADC) scheme for the polarization propagator provides a series of ab initio methods for the calculation of excited states based on perturbation theory. In recent years, the second‐order ADC(2) scheme has attracted attention in the computational chemistry community because of its reliable accuracy and reasonable computational effort in the calculation of predominantly singly excited states. Owing to their size‐consistency, ADC methods are suited for the investigation of large molecules. In addition, their Hermitian structure and the availability of the intermediate state representation (ISR) allow for straightforward computation of excited‐state properties. Recently, an efficient implementation of ADC(3) has been reported, and its high accuracy for typical valence excited states of organic chromophores has been demonstrated. In this review, the origin of ADC‐based excited‐state methods in propagator theory is described, and an intuitive route for the derivation of algebraic expressions via the ISR is outlined and comparison to other excited‐state methods is made. Existing computer codes and implemented ADC variants are reviewed, but most importantly the accuracy and limits of different ADC schemes are critically examined. WIREs Comput Mol Sci 2015, 5:82–95. doi: 10.1002/wcms.1206

This article is categorized under:

Structure and Mechanism > Molecular Structures

Electronic Structure Theory > Ab Initio Electronic Structure Methods

Theoretical and Physical Chemistry > Spectroscopy
Effects of messenger RNA structure and other translational control mechanisms on major histocompatibility complex‐I mediated antigen presentation
Authors: Murat Pierre , Tellam Judy
Published: September 2014

Effective T‐cell surveillance of antigen‐presenting cells is dependent on the expression of an array of antigenic peptides bound to major histocompatibility complex (MHC) class I (MHC‐I) or class II (MHC‐II) molecules. Pathogens co‐evolving with their hosts exploit crucial translational regulatory mechanisms in order to evade host immune recognition and thereby sustain their infection. Evasion strategies that downregulate viral protein synthesis and thereby restrict antigen presentation to cytotoxic T‐cells through the endogenous MHC‐I pathway have been implicated in the pathogenesis of viral‐associated malignancies. An understanding of the mechanisms by which messenger RNA (mRNA) structure modulates both viral mRNA translation and the antigen processing machinery to escape immune surveillance, will stimulate the development of alternative therapeutic strategies focused on RNA‐directed drugs designed to enhance immune responses against infected cells. In this review, we discuss regulatory aspects of the MHC‐I pathway and summarize current knowledge of the role attributed by mRNA structure and other translational regulatory mechanisms in immune evasion. In particular we highlight the impact of recently identified G‐quadruplex structures within virally encoded transcripts as unique regulatory signals for translational control and antigen presentation. WIREs RNA 2015, 6:157–171. doi: 10.1002/wrna.1262

This article is categorized under:

RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems

Translation > Translation Regulation