bluuebunny/crossref_metadata_2025 huggingface dataset:
CONTENT CHARACTERISTICS OF GRE ANALYTICAL REASONING ITEMS
Authors: Chalifour Clark , Powers Donald E.
Published: September 2014

In actual test development practice, the number of test items that must be developed and pretested is typically greater, and sometimes much greater, than the number that is eventually judged suitable for use in operational test forms. This has proven to be especially true for one item type–analytical reasoning–that currently forms the bulk of the analytical ability measure of the GRE General Test.

This study involved coding the content characteristics of some 1,400 GRE analytical reasoning items. These characteristics were correlated with indices of item difficulty, discrimination, and independence from the verbal and quantitative measures.

Several item characteristics were predictive of the difficulty of analytical reasoning items. Generally, these same variables also predicted item discrimination, but to a lesser degree. Independence from the GRE verbal and quantitative measures was largely unpredictable.

The results suggest several content characteristics that could be considered in extending the current specifications for analytical reasoning items. The use of these item features may also contribute to greater efficiency in developing such items. Finally, the influence of these various characteristics also provides a better understanding of the construct validity of the analytical reasoning item type.
NEW TECHNOLOGIES IN CAREER GUIDANCE: THE INTERACTIVE COMPUTER
Authors: Katz Martin R.
Published: September 2014

Beginning in the 1960's, the interactive capabilities of computers provided unprecedented opportunities for the development of computerized career guidance systems. Such systems offered individualized assistance in career decision making to large numbers of people at low cost. Recognizing that each user may present a unique combination of needs, experiences, circumstances, values, interests, skills, styles, and perceptions, a developer can enable a well‐planned system to respond appropriately to these individual differences. A system can not only store, retrieve, and manipulate vast amounts of information, putting great resources at the fingertips of each user, but also bring together many variables – personal, occupational, and educational – and combine them in distinctive ways for each client.

These capabilities do not insure that the substance of any system will be of high quality. Much of a system's worth depends on its conceptual framework, the strength of its theory and rationale, the coherence of its functions and structures. The “black box” of theory underlying every system should be opened up and exposed to the light of scrutiny and evaluation.

Examples from the principles, research, model, and structures for the System of Interactive Guidance and Information (SIGI) and SIGI PLUS are used to illustrate the links between theory and practice.
LATENT STRUCTURE ANALYSIS OF THE TEST OF ENGLISH AS A FOREIGN LANGUAGE
Authors: Boldt Robert F.
Published: September 2014

The results of equating studies are supportive of the use of IRT methods for TOEFL equating, but there remains a discrepancy between the assumptions of the equating and the diversity of the population served. The IRT model assumes that, except for chance effects, the performance of individuals is entirely accounted for by their status on a single latent proficiency variable. But the TOEFL candidate population appears to be sufficiently diverse that different groups might exist, each with its own latent variable. Informal studies indicate that such is the case. The purpose of the study reported here was to identify such groups, if any, and to explore the implications of the results.

The basic and very surprising outcome of this study was the finding that a single factor accounted for virtually all the proportions of joint item successes. This result was obtained for all three TOEFL sections. Also for each section, proportions of joint item success were proportional to the products of the item difficulties. Both of these results indicate that latent group effects are small.

The search for groups also consisted of assessing the relative importance of two factors in accounting for examinees' patterns of item success. For an individual, this relative importance was expressed by the angle in a polar coordinate plot of pairs of coefficients of regression of item scores on factor loadings. A large latent group would appear as a mode in a frequency distribution of angles; multiple modes would indicate several latent groups. But a rather smooth distribution of angles for the total group was found, with some ordering, but a great deal of overlap, of the distributions by national origin and language background. Neither national origin nor native language accounted for more than 25% of the variation in the angles.

The results of the present study are consistent with the use of section equating using item response theory and with the use of the restrictive assumption of proportionality of item response curves; the probability of correct response is a product of two components, a function of ability and an item constant. This is a single parameter model that could serve as a basis for item calibration and equating. The model would lead to simplified procedures. The result also suggests that, when assembling operational tests, using those items for which the proportion of joint successes is most nearly proportional to their difficulties would reduce latent group effects.

The Test of English as a Foreign Language is offered for use by educational institutions with the expectation that the scores from TOEFL examinees are informative on a single scale, essentially without reference to specific examinee characteristics. The present study provides evidence consistent with that expectation. One should be prepared to examine small effects, go outside the domain of measurement, or go outside the typical range of TOEFL examinees to seek substantial departures from the unitary hypothesis.
DIFFERENTIAL ITEM FUNCTIONING ON THE BRAILLE EDITION OF SAT‐M
Authors: Bennett Randy Elliot , Rock Donald A. , Novatkoski Inge
Published: September 2014

This study attempted to pinpoint the causes of differential item difficulty for blind students taking the braille edition of the Scholastic Aptitude Test's Mathematical section (SAT‐M). The study method involved reviewing the literature to identify factors that might cause differential item functioning for these examinees, forming item categories based on these factors, identifying categories that functioned differentially, and assessing the functioning of the items composing deviant categories to determine if the differential effect was pervasive. Results showed an association between selected item categories and differential functioning, particularly for items that included figures in the stimulus, items for which spatial estimation was helpful in eliminating at least two of the options, and items which presented diagrams that were small or medium in size. The precise meaning of this association, however, was unclear because some items from the suspected categories functioned normally, factors other than the hypothesized ones might have caused the observed aberrant item behavior, and the differential difficulty might be related to real population differences.
THE FUTURE OF ITEM ANALYSIS
Authors: Wainer Howard
Published: September 2014

This paper reviews the role of the item in test construction and suggests some new methods of item analysis. A look at dynamic, graphical item analysis is provided that utilizes the advantages of modern high speed, highly interactive computing. Several illustrations are provided.
THE NATIONAL HISPANIC SCHOLAR AWARDS PROGRAM
Authors: Clewell Beatriz Chu , Joy Myra Ficklen
Published: September 2014

The purpose of this study was to

Describe the pool of National Hispanic Scholar Awards Program applicants in the program's initial year, 1983–84, and compare Hispanic Scholars (winners) with Hispanic Honorable Mentions (awardees) and Semifinalists who did not receive an award

Examine the characteristics of high‐achieving Hispanic students

Isolate the factors associated with success in college

To fulfill this purpose, we used data from the Student Descriptive Questionnaire (SDQ), which includes background information on all SAT‐takers, and administered a 12‐page survey to 1983–84 applicants to the program. This survey collected additional information on applicants' academic and educational background, English language use, and experiences during the freshman year in college.

High‐achieving Hispanic students, as represented by applicants to the program, resemble the white cohort of college‐bound students more than they do the Hispanic cohort in terms of socioeconomic background. They received a good academic preparation in high school, had high school GPAs and SAT scores substantially above the mean for either white or Hispanic SAT‐takers, and were well integrated into their high schools. These students attended selective four‐year colleges, where they lived on campus. A large portion majored in physical science and related areas. During their freshman year, although they found college somewhat more difficult than expected, the students encountered few problems, performed well academically, and were active in extracurricular activities.

As a means of isolating factors associated with success in college, three outcome measures were selected to examine freshman‐year performance: academic performance as indicated by first‐year grades; social integration into the college as measured by the number of extracurricular activities during the freshman year; and adjustment to college life as indicated by responses to a question on problems of adjustment. Among the variables we examined, the best predictors of freshman grades were found to be high school GPA and SAT scores. A major in physical science, mathematics, or engineering was predictive of lower grades. Living on campus, number of activities in high school, being male, and living at a distance from the family home were the best predictors of the number of activities in which a student participated in college. High levels of English proficiency and father's education predicted fewer problems in adjustment, while greater distance from home was predictive of more problems. Implications of the findings are discussed, along with recommendations for program modification and general suggestions for further research.
A COMPARISON OF THE STRUCTURAL RELATIONSHIPS AMONG READING, LISTENING, WRITING, AND SPEAKING COMPONENTS OF THE AP FRENCH LANGUAGE EXAMINATION FOR AP CANDIDATES AND COLLEGE STUDENTS1,2
Authors: Morgan Rick , Mazzeo John
Published: September 2014

Yearly the Advanced Placement Program administers an examination to high school students measuring French language skills that students might acquire after six semesters of college French Language courses. The dimensional structure of the 1987 AP French Language exam was tested in four populations using a series of confirmatory linear factor analysis models. In order to mitigate problems associated with the linear factor analysis of multiple‐choice items, the linear factor analysis of item parcel scores, made up of small mutually exclusive collections of items hypothesized to measure the same underlying dimension, was utilized. Six confirmatory factor analysis models were tested within each of five samples of data. Two samples contained high school AP candidates with no out‐of‐school French Language experience. A third sample contained AP candiates which had spent a significant amount of time in a French speaking counry. A fourth sample contained AP candidates who regularly spoke or heard French at home. The final sample contained students with no out‐of‐class French language experience enrolled in third year French classes at one of sixteen colleges. In all samples the exam appears to measure four major dimensions which are associated with the language skills of listening, reading, writing and speaking. For the student groups lacking out‐of‐school French language experience, the structure of the exam displays invariance of factor loadings and errors of measurement. Factor structures were most similar for groups with similar out‐of‐school French language experiences.
SEX GROUP MEMBERSHIP AS A FACTOR IN HANDICAPPED STUDENTS' GRE GENERAL TEST PERFORMANCE
Authors: Bennett Randy Elliot , Rock Donald A. , Jirele Thomas
Published: September 2014

Differences in the performance of handicapped and nonhandicapped students on the GRE General Test as a function of sex group composition were investigated. Hierarchical multiple regression analyses were conducted regressing General Test scores on sex and handicapped group membership, and adjustments to these scores were computed. The resulting adjustments had only minimal effects on handicapped/nonhandicapped mean score differences, suggesting that these disparities cannot be ascribed to differences in sex group distributions. Other plausible explanations for observed score disparities between handicapped and nonhandicapped groups are discussed.
ANALYSIS OF DIFFERENTIAL ITEM FUNCTIONING IN THE NAEP HISTORY ASSESSMENT
Authors: Zwick Rebecca , Ercikan Kadriye
Published: September 2014

The Mantel‐Haenszel approach for investigating differential item functioning (DIF) was applied to U.S. history items that were administered as part of the National Assessment of Educational Progress (NAEP). On some items, Blacks, Hispanics, and females performed more poorly than other students, conditional on number‐right score. It was hypothesized that this resulted in part from the fact that ethnic and gender groups differed in their exposure to the material included in the assessment. Supplementary Mantel‐Haenszel analyses were undertaken in which the number of historical periods studied, as well as score, was used as a conditioning variable. Contrary to expectation, the additional conditioning did not lead to a reduction in the number of DIF items. Both methodological and substantive explanations for this unexpected result were explored.
CONCURRENT VALIDITY OF VERBAL ITEM TYPES FOR ETHNIC AND GENDER SUBGROUPS
Authors: Wild Cheryl L. , McPeek W. Miles , Koffler Stephen L. , Braun Henry I. , Cowell William
Published: September 2014

The validity of the Graduate Record Examinations (GRE) has been a high‐priority research topic. Research to date concerning the GRE verbal measure suggests that for the GRE, as for the Scholastic Aptitude Test, the reading comprehension and sentence completion item types appear to carry the weight of the predictive validity of the verbal measure. However, this finding may have been a result of differences in difficulty and discrimination (as suggested by Schrader [1984a]), rather than a result of inherent differences in the item types.

The purpose of the present study was to examine the verbal item types for the GRE to explore possible reasons for any differences found in subgroup performance and validity. Statistical differences among item types in active forms of the GRE verbal measure were documented, experimental subtests of matching statistical characteristics for the item types were developed, and correlations of the matched and operational item type scores with self‐reported grade point averages were compared. Comparisons were made by gender and ethnic group within undergraduate major field categories.

The results of this study suggest that all the verbal item types studied exhibit concurrent validity. Differences among the item types are small. All the item types are valid, and they are very highly correlated.

Because of this overlapping variance, little concurrent validity is lost by deleting any one item type. Results suggest that, of the four item types, reading comprehension may, overall, be slightly more valid than the other item types. The analogy item type may contribute slightly less than the other item types to the concurrent validity of the verbal measure. However, these differences are small and do not suggest any specific revisions to the verbal measure of the GRE General Test.
ANALYSES OF THE PREDICTIVE VALIDITY OF THE SAT® AND HIGH SCHOOL GRADES FROM 1976 TO 1985
Authors: Morgan Rick
Published: September 2014

Since 1964, colleges have been sending data to the College Board Validity Study Service in order to determine the degree to which measures used in admissions predict college performance. These studies have allowed for the monitoring of general trends in the relationship of SAT scores and high school grades with freshman grades. Beginning in the early‐1970s and continuing to the mid‐1970s, the observed average correlations of SAT scores with freshman grades increased dramatically. In the decade that followed, the strength of this relationship gradually declined. In order to determine to what extent the observed variations in the average correlations might be associated with the composition of colleges conducting validity studies each year, validity data were analyzed for the enrolling classes of 1976 to 1985. Estimates of change, based on a repeated measures estimation approach utilizing data from colleges conducting more than one predictive validity study within the 10‐year period, and correcting for the restriction of range in SAT scores and high school record, indicated a general linear trend from 1976 to 1985. The correlations of SAT scores with first‐year college grades declined from about .51 to about .47, for a change of approximately .04, There was less change during this period for private colleges, small colleges, and more selective colleges.
TOWARD A DESCRIPTION OF SUCCESSFUL GRADUATE STUDENTS
Authors: Enright Mary K. , Gitomer Drew
Published: September 2014

At present, the role of testing in education is being radically reevaluated. Advances in cognitive science suggest new approaches to assessment based on a better understanding of the nature of successful performance. Tests, that have been used primarily for prediction and selection are now viewed as having the potential to become more relevant to, and integrated with, the educational process. Such tests, however, require rethinking what should be measured and how it should be assessed.

In this report, a broad understanding of the skills and characteristics associated with successful performance in graduate school was developed through discussions with two groups of distinguished graduate faculty members. The first group consisted of eminent psychologists with expertise in cognition and assessment. The second group was composed of distinguished faculty from other fields, including the humanities, social sciences, and physical sciences.

These discussions had four major outcomes. The first was a characterization of the graduate education process as a form of apprenticeship that was suggestive of the kinds of skills and characteristics that contribute to success in many graduate programs. Based on this description, the second outcome was the identification of critical skills associated with scholarly and professional competence that are not currently measured by graduate admissions tests. A tentative list of seven competencies thought to be important for success in academic graduate programs and in subsequent professional roles was developed. The competencies include communication, creativity, explanation, motivation, planning, professionalism, and synthesis.

The last two outcomes concerned how these competencies might be assessed. One was a recommendation that discipline‐specific simulation testing would be a useful tool that would permit the identification and concrete definition of skills associated with superior performance, contribute to the development of a theory of success in graduate school, and encourage the development of assessment techniques with well‐established construct validity and educational relevance. Finally, potential exercises that would provide opportunities for students to display these competencies were proposed.
PASSING THE NTE: A CLASSIFICATION OF STATE REQUIREMENTS AND PASSING RATES, BY ETHNICITY
Authors: DeMauro Gerald E.
Published: September 2014

It is difficult to estimate the percentage of examinees who “pass” NTE tests because the many users of the tests not only require examinees to pass different combinations of tests, but also use different passing scores for each of the tests. Earlier studies (e.g., Goertz and Pitcher, 1985) computed passing rates for individual tests by applying specific passing scores to national distributions of examinees. However, none of these studies computed the percentage of examinees who passed all the NTE tests required for any state. This study first develops a taxonomy of state NTE requirements. The passing rates for each type of state requirement are then computed both for the examinee group that is impacted by the requirement and for each self‐identified ethnic group. For example, one type of requirement is found in states that require teacher certification candidates to pass all three Core Battery tests and the Specialty Area test most relevant to their area of interest. For this type of requirement, the percentage of examinees who pass each test is computed as well as the percentage of examinees who pass all of the required tests. These percentages are computed for all examinees who sent their scores to states of this type and separately for the self‐identified Black, Hispanic, “Other,” Unknown, and White examinees in this group. Results show considerable variation in passing rates depending on types of requirements and passing scores, and variation in ethnic differences in passing rates. The ratio of percentages of self‐identified Black examinees who pass each requirement to percentages of self‐identified White examinees who pass each requirement is related to both the passing scores used and the particular group of required tests. The study provides a methodology and data base for further research in this area, and raises important policy issues for consideration.
Alkaline peroxide electrosynthesis by oxygen reduction using an acid anolyte in a divided reactor with a three‐dimensional rotating cylinder cathode and two‐phase flow induced by centrifugal force
Authors: González Pérez Omar , Bisang José M
Published: September 2014

BACKGROUND

This work analyses the performance of a batch electrochemical reactor with a three‐dimensional rotating cylinder cathode for the synthesis of alkaline peroxide by reduction of O2 under 0.1 MPa (abs). The centrifugal force produces a radial co‐current flow of the gas and liquid phases through the cathode achieving good mass‐transfer conditions for the O2 reduction.

RESULTS

Galvanostatic experiments carried out during 2 h at 2 A (macrokinetic current density 398 A m−2), 30°C and 1000 rpm with 1 mol L−1 H2SO4 as anolyte demonstrates that the cationic exchange membrane Nafion® 415 is an appropriate separator. However, a small decrease in the alkalinity of the cathodic compartment was observed. The use as anolyte of an equimolar solution of Na2SO4 and H2SO4 (1 mol L−1) maintains constant the total alkalinity of the cathodic solution. An experiment of 6 h yielded 10.3 g L−1 H2O2 concentration with 62.3% current efficiency and 10.6 kWh kg−1 specific energy consumption, using Na2SiO3 as addition agent.

CONCLUSION

A divided electrochemical reactor using an acid anolyte and a three‐dimensional rotating cylinder cathode with co‐current oxygen and liquid flows represents a simple strategy for localized generation of peroxide solutions with low total alkalinity. © 2014 Society of Chemical Industry
Dual band inverted L‐shape monopole antenna for cellular phone applications
Authors: Sambhe Vijay K. , Awale R. N. , Wagh Abhay
Published: September 2014

To mitigate the requirement of dual band cellular phone applications, inverted L‐shaped monopole antenna is proposed in this article. The proposed antenna have optimum dimensions 22 (L) × 76 (W) × 1.6 (h) mm3 and fabricated on easily available FR4 substrate with permittivity 4.4 and loss tangent is 0.02. The structure is feed to 50‐Ω microstrip line and terminated with SMA connector. The antenna covers 824–894 MHz (AMPS), 890–960 MHz (GSM) in lower frequency bands, and 2–2.5 GHz (Wi‐Fi, Bluetooth, WiMAX) in upper frequency bands. Measured VSWR is ≤2 for both dual band of frequencies. The antenna shows acceptable gain flatness from 1.5 to 3.59 dBi with good omnidirectional radiation pattern. In addition, an attempt is made to investigate the effect of L‐patch on the impedance bandwidth with extensive simulation and result are presented. The antenna offers high efficiency for both dual frequency bands and easy integration with the other microwave circuits. Its simplicity, gain flatness, and radiation patterns make it suitable for dual band cellular phone applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2751–2755, 2014
An analysis of electromagnetic interference on RF circuits based on electromagnetic topology
Authors: Kang Won‐June , Lee Kang‐In , Shin Jin‐Woo , So Joon‐Ho , Chung Young‐Seek
Published: September 2014

In this article, we propose a method of analysis of the intentional electromagnetic interference (IEMI) in radio frequency circuits that are directly exposed to an external electromagnetic wave, using electromagnetic topology (EMT). EMT solves IEMI problems, by a fast and efficient transformation of the main penetrating channels of the external electromagnetic wave in the target, into general equivalent transmission lines. To handle nonlinear devices, we combined EMT with the harmonic balance method, by applying the least square method to the experimental data of the devices. To verify the proposed method, we applied it to microstrip line circuits with passive loads, a dipole antenna, and a low noise amplifier, and compared the results with the experimental ones. The two results were in good agreement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2784–2789, 2014
Design of a spectroscopic ellipsometer by synchronous rotation of the polarizer and analyzer in opposite directions
Authors: El‐Agez Taher M. , Taya Sofyan A.
Published: September 2014

In this article, a spectroscopic ellipsometer is constructed in rotating polarizer and analyzer configuration. Instead of continuous rotation and integration for waveform analysis, a step and scan method was adopted for both the rotating polarizer and the rotating analyzer and Fourier analysis was used for the waveform analysis. In this system, the polarizer and the analyzer rotate in opposite directions with the same angular speed. The transmission axes of the two elements are rotated using microstepping motors. The accuracy of the constructed ellipsometer is tested using two ellipsometry standards with different thicknesses. Commercial software for thin film analysis (TFCompanion‐optical metrology software) obtained from Semiconsoft, Inc. is used to analyze the experimental results. The results reveal a high accuracy device for thin film characterization. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2822–2826, 2014
Boresight gain enhancement of planar stair‐like UWB monopole antenna
Authors: Thajudeen Christopher , Zhang Wenji , Hoorfar Ahmad
Published: September 2014

A novel configuration of a compact stair‐like ultrawideband (UWB) planar monopole antenna is presented for improved boresight gain performance and pattern stability. The geometry of the basic antenna has been modified to include a gate‐like ground plane structure which alleviates unwanted squinting effects in the gain pattern at higher frequencies. The boresight gain is then further enhanced through the addition of a stacked parasitic patch composed of a scaled copy of the basic stair‐like geometry. Prototypes of the proposed antenna geometries are fabricated and measured to validate the concept. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2809–2812, 2014
Novel quad‐band filter with high frequency ratio and controllable bandwidths using SLHSIRs and SLQSIRs
Authors: Zhang Zhi‐chong , Chu Qing‐Xin , Chen Fu‐Chang
Published: September 2014

This article presents a quad‐band bandpass filter (QB‐BPF) using a set of stub‐loaded half‐wavelength step impedance resonators operated at the second and third passbands (2.4/3.5 GHz) and a set of stub‐loaded quarter‐wavelength step impedance resonators operated at the first and fourth passbands (1.3/5.8 GHz), and the frequency ratio is 4.46 times. Furthermore, all the frequencies and bandwidths can be adjusted. Finally, the proposed filter is designed and fabricated. The measured results are in good agreement with the full‐wave simulation results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2845–2848, 2014
Miniaturized band stop filter using swirl‐type microstrip transmission line based on dual CRLH structure
Authors: Yang Doo‐Yeong , Seo Soo‐Duk , Kim Jeongpyo
Published: September 2014

The swirl‐type unit cell with a dual composite right/left‐handed property on microstrip transmission line is proposed. The equivalent circuit of the proposed unit cell has been derived from the physical geometry of swirl‐type shape. The unit cell with a compact size has good characteristics and has been used in the miniaturized filter design. Therefore, the band stop filter has been designed by cascading several swirl‐type cells and implemented on microstrip transmission line. The simulated and the measured results show good agreements in interest band. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2867–2871, 2014
Interrogation and multiplexing system for fiber loop mirror coupled intensity sensors using OTDR
Authors: Giraldi Maria Thereza M. Rocco , Fernandes Cindy S. , Ferreira Marta S. , de Sousa Marco J. , Jorge Pedro , Costa João C. W. A. , Santos José L. , Frazão Orlando
Published: September 2014

In this article, it is proposed an interrogation and multiplexing system based on optical time domain reflectometer for fiber loop mirror coupled intensity sensors. Pulse width of approximately 100 ns enabled to attain a dynamic range of approximately 18 dB. Good linearity was achieved with a −13.3 dB/mm slope. The resolution of the sensing head was 0.027 mm. The proposed interrogation system showed to be an alternative technique for multiplexing and remote sensing. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2860–2864, 2014
Microwave mixer using microstrip circular disk configuration
Authors: Kumar Arun , Ray Sudhabindu
Published: September 2014

In this article, design of a diode‐based mixer using microstrip circular disk resonator patch is described. A mixer working in down‐conversion mode having minimum conversion loss of 8.8 dB with +10 dBm local oscillator (LO) power and 3 dB radio frequency bandwidth of 100 MHz has been achieved at S‐band. The novelty of the mixer is that it has inherent LO to intermediate frequency (IF) isolation greater than 17 dB without using an IF low pass filter. A systematic design of the mixer is presented with its simulated and experimental results. The mixer design concept presented here can be applied to design mixers at other frequencies. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2871–2874, 2014
Wideband bandpass filter with a broad stopband based on a triple‐mode stub‐loaded resonator
Authors: Wei Feng , Guo Y. Jay , Qin Pei‐Yuan , Shi Xiao Wei
Published: September 2014

A compact wideband bandpass filter (BPF) with a broad stopband (4.1 f0) based on a triple‐mode stub‐loaded resonator (SLR) is presented in this article. Using even/odd mode analysis, the proposed SLR is found to have the ability to introduce three transmission poles in the passband. By appropriately adjusting the frequencies of these transmission poles and using a 0° tapped feed structure, the BPF can provide a wide passband and a sharp rejection over a broad stopband without using other lowpass or bandstop networks. The predicted results on S‐parameters are compared with measured ones and good agreement is achieved. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2878–2881, 2014
A tri‐band bandpass filter using stub‐loaded SIRS with controllable bandwidths
Authors: Cho Young‐Ho , Yun Sang‐Won
Published: September 2014

In this article, we present a tri‐band bandpass filter (BPF) based on a stub‐loaded stepped‐impedance resonator (SIR). The proposed resonator has the compact size based on a short‐circuited SIR as well as the controllability of three resonant frequencies by adjusting impedance ratios. Bandwidths for the first and second passbands can be independently controlled using two coupling paths between resonators, while the third bandwidth can be designed by adjusting dimensions of an open‐stub loaded to the resonator. Two‐pole tri‐band BPF is designed and tested at center frequencies of 1.575, 2.4, and 3.5 GHz with fractional bandwidths of 10%, 6%, and 4%, respectively. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2907–2910, 2014
High CM suppression wideband balanced microstrip BPF using dual‐mode resonator
Authors: Deng Hong‐Wei , Zhao Yong‐Jiu , He Ying , Liu Hao , Wang Hong‐Li
Published: September 2014

In this letter, a novel high selectivity and common‐mode (CM) suppression wideband balanced microstrip passband filter (BPF) is proposed using the short stub centrally loaded short‐ended resonators (SSCLSR). The odd‐mode resonant frequency of the SSCLSR can be flexibly controlled by the short stub, whereas the even‐mode one is fixed. First, the wideband single‐ended BPF are designed based on the microstrip SSCLSR with the parallel coupled microstrip line input/output (I/O). Two transmission zeros near the passband edges can be generated due to the main path signal counteraction and source‐loaded coupling. Further, the CM equivalent half circuits of the balanced BPF based on the wideband single‐ended BPF are investigated in detail. Thus, a wideband balanced BPF with high CM suppression within the passband is designed, fabricated, and measured. Good agreement between simulated and measured results is obtained. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2940–2944, 2014
Dual‐band matching of arbitrary loads
Authors: Lehtovuori Anu , Valkonen Risto , Valtonen Martti
Published: September 2014

This article presents a systematic approach for dual‐band impedance matching of an arbitrary load using two matching circuits designed separately for the desired passbands as the basis. Exact transform equations for converting the obtained single‐band matching circuits into a dual‐band matching circuit can be applied to any kind of load impedance with arbitrary frequency‐dependency. The matching and impedance levels can be chosen individually for both passbands. The examples on the dual‐band matching of coupling‐element antennas demonstrate that also wide bandwidths can be achieved. The presented equations facilitate designing multiband matching circuits and are feasible also for solving double matching problems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2958–2966, 2014
Temperature influence of matching liquid in a microwave tomography platform system
Authors: Kim J. Y. , Lee K. J. , Son S. H. , Jeon S. I. , Kim N.
Published: September 2014

The temperature influence of the matching liquid used in the microwave tomography platform system working from 3 to 6 GHz was analyzed on the article. The temperature impact of the matching liquid was found using the measured signal data. If the temperature of the matching liquid is maintained ideally, the measured signal data are obtained the stable data. But, the acquired signal data are obtained the unstable data because the temperature of matching liquid can not be maintained naturally. To obtain the stable data, the temperature control devices are required to maintain the temperature of matching liquid. Furthermore, the temperature variation of the matching liquid in the platform system is the important factor aimed for breast cancer detection. How much impact happened by the temperature variation was studied to overcome the temperature influence of the matching liquid. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2978–2981, 2014
High selectivity and CM suppression wideband balanced BPF
Authors: Deng Hong‐Wei , Zhao Yong‐Jiu , He Ying , Liu Hao , Wang Hong‐Li
Published: September 2014

In this letter, a novel wideband balanced bandpass filter (BPF) with high selectivity and common‐mode (CM) suppression is constructed with slotline resonator. When the intersection points of the microstrip feedline and slotline resonator are close to the midpoint of the slotline resonator, the coupling between the second mode and microstrip feedline can be suppressed. Making use of this feature, the wideband single‐ended filter with wide upper‐stopband performance is designed using the slotline resonators and two quarter‐wavelength microstrip resonators paralleled to the slotline resonator with tapped‐line coupling at their short‐circuited ends. Further, high‐selectivity fifth‐order wideband single‐ended filter and corresponding balanced BPF are designed with parallel coupling structures between two slotline resonators. The fifth‐order wideband balanced filter is designed and fabricated, and good agreement between measurements and simulations is obtained. The measured CM suppressions are better than 54 dB within the whole differential‐mode passband. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2998–3003, 2014
Array of spatial power combination for wide angle sector coverage
Authors: Chang Le , Zhang Zhijun , Li Yue , Feng Zhenghe
Published: September 2014

This study investigates the feasibility of using spatial power combination in small‐scale array applications that require sector coverage. A patch antenna array is used to verify the concept. The simulated result of the proposed array shows that the −6 dB angle coverage is 132° from 24° to 156° in elevation plane and the −10 dB return loss bandwidth is 4.6%. The optimized measured result indicates that the −6 dB angle coverage is 134° from 20° to 154° in elevation plane. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2990–2993, 2014
Characteristics of optical glass plate refractive index sensor based on surface plasmon resonance
Authors: Tang Cien‐Jen , Lin Chen‐Hung , Hsiao Li‐Jen , Chen Wei‐Tsung , Jaing Cheng‐Chung , Lin Hoang Yan
Published: September 2014

This work presents a novel refractive index sensor structure based on surface plasmon resonance, consisting of planar glass plates coated with multilayer thin film. The glass plate guides the light, the multilayer metallic thin film excites the surface plasmon wave, and the dielectric film is used to fine tune the resonance wavelength. The resolution and spectrum variation and the wavelength shift, for aqueous solutions of salt of various concentrations, are measured. The sensor resolution and sensitivity is obtained. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:3009–3012, 2014
Bandpass filter with stepped impedance subharmonic stubs
Authors: Malherbe J. A. G. , Mphiwe Christina
Published: September 2014

Structures with shunt stubs in a subharmonic ratio that realize bandpass performance have limited application due to the inherent problem of fixed transmission zero positions in the stopband. By application of the principle of splitting, the subharmonic stubs into cascades of transmission line sections, structures can be realized that have transmission zeros at arbitrary positions. A bandpass filter employing stepped impedance stubs is developed, and it is shown that moderate bandwidth can be achieved. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:3012–3015, 2014
Design of a 77‐GHz radar frontend module
Authors: Park Sangwook , Kwon Manseok , Kam Dong Gun
Published: September 2014

This article describes a method to design an automotive radar frontend module that deals with the routing of 77‐GHz signals on a low‐cost printed circuit board including wire‐bond and rectangular waveguide‐to‐microstrip transitions. The operation of the developed modules was successful in the first attempt, showing good model‐to‐hardware correlation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:3015–3020, 2014
ESR and calculations on electronic structure of phenalenyl and phenalenyl derivative radicals
Authors: Piccinato Marilene Turini , da Costa Marcello Ferreira , Ota André Tsutomu , Guedes Carmen Luísa Barbosa , Di Mauro Eduardo
Published: September 2014

Calculations on electronic structure of the perinaphthenyl radical and phenalenyl derivative radicals responsible for the composition of the ESR spectrum of marine diesel under heating were performed to obtain support for the experimental ESR results. The parameters calculated were the hyperfine coupling constants (A), which were then used for comparison with the experimental data. The energy‐minimized structures were obtained using the density functional theory method. In all cases, the symmetry system was taken into account in theoretical calculations. The differences between experimental and theoretical values were below 7% for nearest hydrogens in molecules, named hyperfine coupling constant A (first neighbors) and 18% for farthest hydrogens atoms named hyperfine coupling constants A′ (second neighbors), for all structures analyzed. Copyright © 2014 John Wiley & Sons, Ltd.
Structure of pravastatin and its complex with sodium dodecyl sulfate micelles studied by NMR spectroscopy
Authors: Galiullina L. F. , Rakhmatullin I. Z. , Klochkova E. A. , Aganov A. V. , Klochkov V. V.
Published: September 2014

The aim of this work was to study the mechanisms of interaction between pravastatin and cell membranes using model membranes (sodium dodecyl sulfate micelles) by nuclear magnetic resonance spectroscopy methods. On the basis of the nuclear magnetic resonance experiments, it was established that pravastatin can form intermolecular complexes with sodium dodecyl sulfate micelles by the interaction of its hydrophilic groups with the polar surface of the micelle. Conformational features of pravastatin molecule were also studied. Copyright © 2014 John Wiley & Sons, Ltd.
Evaluation of segmented 3D acquisition schemes for whole‐brain high‐resolution arterial spin labeling at 3 T
Authors: Vidorreta Marta , Balteau Evelyne , Wang Ze , De Vita Enrico , Pastor María A. , Thomas David L. , Detre John A. , Fernández‐Seara María A.
Published: September 2014

Recent technical developments have significantly increased the signal‐to‐noise ratio (SNR) of arterial spin labeled (ASL) perfusion MRI. Despite this, typical ASL acquisitions still employ large voxel sizes. The purpose of this work was to implement and evaluate two ASL sequences optimized for whole‐brain high‐resolution perfusion imaging, combining pseudo‐continuous ASL (pCASL), background suppression (BS) and 3D segmented readouts, with different in‐plane k‐space trajectories.

Identical labeling and BS pulses were implemented for both sequences. Two segmented 3D readout schemes with different in‐plane trajectories were compared: Cartesian (3D GRASE) and spiral (3D RARE Stack‐Of‐Spirals). High‐resolution perfusion images (2 × 2 × 4 mm3) were acquired in 15 young healthy volunteers with the two ASL sequences at 3 T. The quality of the perfusion maps was evaluated in terms of SNR and gray‐to‐white matter contrast. Point‐spread‐function simulations were carried out to assess the impact of readout differences on the effective resolution.

The combination of pCASL, in‐plane segmented 3D readouts and BS provided high‐SNR high‐resolution ASL perfusion images of the whole brain. Although both sequences produced excellent image quality, the 3D RARE Stack‐Of‐Spirals readout yielded higher temporal and spatial SNR than 3D GRASE (spatial SNR = 8.5 ± 2.8 and 3.7 ± 1.4; temporal SNR = 27.4 ± 12.5 and 15.6 ± 7.6, respectively) and decreased through‐plane blurring due to its inherent oversampling of the central k‐space region, its reduced effective TE and shorter total readout time, at the expense of a slight increase in the effective in‐plane voxel size. Copyright © 2014 John Wiley & Sons, Ltd.
Synthesis of AB3‐type miktoarm star polymers with steroid core via a combination of “Click” chemistry and ring opening polymerization techniques
Authors: Doganci Erdinc , Gorur Mesut , Uyanik Cavit , Yilmaz Faruk
Published: September 2014

Well‐defined AB3‐type miktoarm star‐shaped polymers with cholic acid (CA) core were fabricated with a combination of “click” chemistry and ring opening polymerization (ROP) methods. Firstly, azide end‐functional poly(ethylene glycol) (mPEG), poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(ε‐caprolactone) (PCL) polymers were prepared via controlled polymerization and chemical modification methods. Then, CA moieties containing three OH groups were introduced to these polymers as the end groups via Cu(I)‐catalyzed click reaction between azide end‐functional groups of the polymers (mPEG‐N3, PMMA‐N3, PS‐N3, and PCL‐N3) and ethynyl‐functional CA under ambient conditions, yielding CA end‐functional polymers (mPEG‐Cholic, PMMA‐Cholic, PS‐Cholic, and PCL‐Cholic). Finally, the obtained CA end‐capped polymers were employed as the macroinitiators in the ROP of ε‐caprolactone (ε‐CL) yielding AB3‐type miktoarm star polymers (mPEG‐Cholic‐PCL3, PMMA‐Cholic‐PCL3, and PS‐Cholic‐PCL3) and asymmetric star polymer [Cholic‐(PCL)4]. The chemical structures of the obtained intermediates and polymers were confirmed via Fourier transform infrared and 1H nuclear magnetic resonance spectroscopic techniques. Thermal decomposition behaviors and phase transitions were studied in detail using thermogravimetric analysis and differential scanning calorimetry experiments. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3390–3399
Effect of specific plant‐growth‐promoting rhizobacteria (PGPR) on growth and uptake of neonicotinoid insecticide thiamethoxam in corn (Zea mays L.) seedlings
Authors: Myresiotis Charalampos K , Vryzas Zisis , Papadopoulou‐Mourkidou Euphemia
Published: September 2014

BACKGROUND

Corn (Zea mays L.) is one of the most important cereal crops in the world and is used for food, feed and energy. Inoculation with plant‐growth‐promoting rhizobacteria (PGPR) would reduce the use of chemical fertilisers and pesticides and could be suggested as an alternative practice for sustainable production of corn in modern agricultural systems. In this study, the effect of two Bacillus PGPR formulated products, Companion® (B. subtilis GB03) and FZB24® (B. subtilis FZB24), on corn growth and root uptake of insecticide thiamethoxam was investigated.

RESULTS

All bacterial treatments enhanced root biomass production by 38–65% compared with the uninoculated control, with no stimulatory effect of PGPR on above‐ground biomass of corn. The uptake results revealed that, in plants inoculated with the PGPR B. subtilis FZB24 and B. subtilis GB03, singly or in combination, the uptake and/or systemic translocation of thiamethoxam in the above‐ground corn parts was significantly higher at the different growth ages compared with the control receiving no bacterial treatment.

CONCLUSION

The findings suggest that the PGPR‐elicited enhanced uptake of thiamethoxam could lead to improved efficiency of thiamethoxam using reduced rates of pesticides in combination with PGPR as an alternative crop protection technique. © 2014 Society of Chemical Industry