bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrokinetic energy conversion in nanofluidic channels: Addressing the loose ends in nanodevice efficiency
Authors: Bakli Chirodeep , Chakraborty Suman
Published: September 2014

We bring out a nontrivial coupling of the intrinsic wettability, surface charge, and electrokinetic energy conversion characteristics of nanofluidic devices. Our analyses demonstrate that nanofluidic energy conversion efficiencies may get amplified with increase in surface charge density, not perpetually, but only over a narrow regime of low surface charges, and may get significantly arrested to reach a plateau beyond a threshold surface charging condition, as attributed to a complex interplay between fluid structuration and ionic transport within a charged interfacial layer. We explain the corresponding findings from our molecular dynamics simulations with the aid of a simple modified continuum based theory. We attribute our findings to hitherto‐unexplored four‐way integration of surface charge, interfacial slip, ionic transport, and the water molecule structuration. The consequent complex nonlinear nature of the energy transfer characteristics may bear far‐ranging scientific and technological implications toward design, synthesis, and operation of futuristic energy conversion devices of molecular length scales.
Multidimensional capillary electrophoresis
Authors: Grochocki Wojciech , Markuszewski Michał J. , Quirino Joselito P.
Published: September 2014

Multidimensional separation where two or more orthogonal displacement mechanisms are combined is a promising approach to increase peak capacity in CE. The combinations allow dramatic improvement of analytical performance since the total peak capacity is given by a product of the peak capacities of all methods. The initial reports were concentrated on the construction of effective connections between capillaries for 2D analysis. Today, 2D and 3D CE systems are now able to separate real complex biological or environmental mixtures with good repeatability, improved resolution with minimal loss of sample. This review will present the developments in the field of multidimensional CE during the last 15 years. The endeavors in this specific field were on the development of interfaces, interface‐free techniques including integrated separations, microdevices, and on‐line sample concentration techniques to improve detection sensitivity.
Succinate production from xylose‐glucose mixtures using a consortium of engineered Escherichia coli
Authors: Xia Tian , Altman Elliot , Eiteman Mark A.
Published: September 2014

The conversion of variable sugar mixtures into biochemicals poses a challenge for a single microorganism. For example, succinate has not been effectively generated from mixtures of glucose and xylose. In this work, a consortium of two Escherichia coli strains converted xylose and glucose to succinate in a dual phase aerobic/anaerobic process. First, the optimal pathway from xylose or glucose to succinate was determined by expressing either heterologous pyruvate carboxylase or heterologous adenosine triphosphate‐forming phosphoenol pyruvate (PEP) carboxykinase. Expression of PEP carboxykinase (pck) resulted in higher yield (0.86 g/g) and specific productivity (155 mg/gh) for xylose conversion, while expression of pyruvate carboxylase (pyc) resulted in higher productivity (76 mg/gh) for glucose conversion. Then, processes using consortia of the two optimal xylose‐selective and glucose‐selective strains were designed for two different feed ratios of glucose/xylose. In each case the consortia generated over 40 g/L succinate efficiently with yields greater than 0.90 g succinate/g total sugar. This study demonstrates two advantages of microbial consortia for the conversion of sugar mixtures: each sugar‐to‐product pathway can be optimized independently, and the volumetric consumption rate for each sugar can be controlled independently, for example, by altering the biomass concentration of each consortium member strain.
A COMPARATIVE STUDY OF STANDARD‐SETTING METHODS
Authors: Livingston Samuel A. , Zieky Michael J.
Published: September 2014

The borderline‐group method and the contrasting‐groups method were each compared with Nedelsky's method at four schools and with Angoff's method at another four schools, using tests of basic skills in reading and mathematics. The borderline‐group and contrasting‐groups methods produced similar results when approximately equal numbers of students were classified as masters and nonmasters. The contrasting‐groups passing score was lower than the borderline‐group passing score when masters greatly outnumbered nonmasters; higher when nonmasters outnumbered masters. Results involving the Nedelsky and Angoff methods were not consistent across schools. Passing scores tended to be higher at schools where students were more able.
A STATISTICAL METHOD FOR IDENTIFYING RACIAL OVERREPRESENTATION IN SPECIAL EDUCATION PLACEMENT
Authors: Jones Douglas H. , Bennettand Randy Elliot , Sacks Jerome
Published: September 2014

The discovery of disproportionate minority enrollments in special education classes has been a subject of considerable concern to federal, state, and local education officials alike for the past decade. Because the existence of disproportions is frequently thought to result from discriminatory placement practices on the part of local school districts, many state agencies are implementing methods for detecting and taking action against offending districts. This paper discusses some of the methodological problems inherent in existing methods for determining disparities in special education placement and offers an alternative to presently‐used methods. The alternative offered can be used for the simultaneous comparison of disparity across many districts and several diagnostic categories.
AN EXPLORATORY STUDY OF THE APPLICABILITY OF ITEM RESPONSE THEORY METHODS TO THE GRADUATE MANAGEMENT ADMISSION TEST1
Authors: Kingston Neal , Leary Linda , Wightman Larry
Published: September 2014

A necessary prerequisite to the operational use of item response theory (IRT) in any testing program is the investigation of the feasibility of such an approach. This report presents the results of such research for the Graduate Management Admission Test (GMAT).

Despite the fact that GMAT data appear to violate a basic assumption of the three‐parameter logistic item response model, local independence, the model was able to replicate accurately the observed item responses. IRT‐based equating was consistent across two randomly selected samples and four selected subpopulations (male, female, younger examinees, and older examinees) and produced converted scores very similar to those produced by the current GMAT equating method — linear section pre‐equating — a method that makes different assumptions than those required by IRT. It appears that for GMAT item types and populations, any effect of the violation of local independence on IRT true‐score equating is negligible.

This research has shown IRT equating to be feasible for the GMAT; but, because the local independence assumption of IRT appears to be violated, further experience is needed before other IRT methods — such as optimal test development, using item information, or computerized adaptive testing — could be used for the GMAT.
REGIONAL DEPENDENCE FOR CONTINUOUS BIVARIATE DENSITIES
Authors: Holland Paul W. , Wang Yuchung J.
Published: September 2014

When the region of support for a continuous bivariate density is not a cartesian product set, the joint distribution cannot be independent. This is closely related to the effects caused by “structural zeros” in two‐way contingency tables. Nonrectangular regions of support for continuous densities are analogous to the incomplete two‐way tables. Quasi‐independence is introduced to replace independence. A measure of association to quantify the degree of dependence due to region is defined, discussed, and applied to several examples.
CATS, TESTLETS, AND TEST CONSTRUCTION: A RATIONALE FOR PUTTING TEST DEVELOPERS BACK INTO CAT
Authors: Wainer Howard , Kiely Gerard L.
Published: September 2014

It is observed that many sorts of difficulties preclude the uneventful construction of tests by a computerized algorithm, such as those currently in favor in Computerized Adaptive Testing (CAT). In this essay we discuss a number of these problems as well as some possible avenues of solution. We conclude with the development of the ‘testlet’, a bundle of items that can be arranged either hierarchically or linearly, which maintains the efficiency of an adaptive test while simultaneously keeping the quality control of test construction that is only possible currently with careful expert scrutiny.
THE POTENTIAL DUAL EFFECT OF CONTEXT EFFECTS AND SCORE LEVEL EFFECTS ON THE ASSIGNMENT OF SCORES TO ESSAYS
Authors: Paden Patricia A.
Published: September 2014

This paper represents a systematic treatment of the potential dual effect of the context in which an essay is reread and the previously assigned score (value) of that essay on the subsequently assigned essay score. This effect is theorized in a formula referred to as “essay score change” (ESC). Examples of the possible utility of the ESC index are outlined. Tentative hypotheses for investigating and interpreting possible essay score change in light of potential dual effects of context and score level are discussed.
APPLICATION OF A NEW GOODNESS‐OF‐FIT PLOT PROCEDURE TO SAT AND TOEFL ITEM TYPE DATA1,2,3
Authors: Eignor Daniel R. , Golub‐Smith Marna , Wingersky Marilyn S.
Published: September 2014

The three‐parameter logistic IRT model is currently being used for equating purposes with data from multiple administrations of two testing programs at ETS: the Admissions Testing Program Scholastic Aptitude Test (SAT) and the Test of English as a Foreign Language (TOEFL). Users of the model in these two testing programs have generally assessed goodness of fit of the model to test items by looking at item‐estimated ability regression plots. This procedure tends to be fairly subjective and quite time consuming, and as a result, little useful aggregate data have been assessed that would shed light on which SAT‐Verbal, SAT‐Mathematical, and TOEFL item types are better or more poorly fit by the model.

The purposes of this study were two‐fold: 1) to systematically study the fit of the three‐parameter logistic model to SAT and TOEFL item type data, using a fit statistic formed by grouping on estimated ability and a newly suggested normal probability plot procedure; and 2) to determine the degree of consistency that can be expected when assessing lack of fit of the three‐parameter model using the fit statistic formed by grouping on estimated ability and a newly suggested fit statistic which is formed by grouping an observed number‐right score.
THE IMPACT OF DIFFERENT ABILITY DISTRIBUTIONS ON IRT PREEQUATING1,2,3
Authors: Stocking Martha L. , Eignor Daniel R.
Published: September 2014

Item response theory preequating depends upon item parameter estimate invariance. The impact of differences in true ability on the invariance properties of item parameter estimates was studied with simulated data. Using real SAT‐mathematical data that had produced unsatisfactory preequating results to suggest hypotheses, three explanatory models were investigated: 1) differences in mean true ability, 2) a certain type of multidimensionality, and 3) a combination of differences in mean true ability and multidimensionality. This latter model produced results consistent with the real data.
HANDICAPPED APPLICANTS TO COLLEGE: AN ANALYSIS OF ADMISSIONS DECISIONS
Authors: Willingham Warren W.
Published: September 2014

ABSTRACT

Federal regulations protect the rights of handicapped students regarding admissions testing and the admissions process generally. The purpose of this study was to compare admissions decisions of handicapped and nonhandicapped applicants who have comparable Scholastic Aptitude Test (SAT) scores and high school grades (HSG). The main finding was that handicapped applicants were admitted on much the same basis as nonhandicapped applicants, but there were exceptions that favored hearing impaired applicants, disfavored small groups of visually impaired and physically handicapped applicants to small institutions, and disfavored learning disabled applicants to a small degree. The results appeared inconsistent with the assumption that colleges give special attention to flagged test scores of handicapped applicants.
SAT TESTING TIME FOR STUDENTS WITH DISABILITIES
Authors: Packer Jaclyn
Published: September 2014

This study examined the amount of time used by disabled students to take special administrations of the SAT offered by the College Board's ATP Services for Handicapped Students. It also investigated the relationship between length of time taken and scores achieved.

Timing data on groups of students were examined, both by disability and by the version of the test taken (braille, cassette, large type or regular type). Results showed that disabled students who were tested over the four years from 1979 to 1983 took considerably more time to complete the SAT than non‐disabled students. Hearing impaired students taking a regular version of the test took the smallest amount of time, averaging 3.7 hours, while visually impaired students taking a cassette version averaged 5.4 hours and those taking a braille version averaged 6.0 hours. Physically disabled and learning disabled students averaged between 4.3 and 4.7 hours.

Time spent on each section of the SAT (two verbal sections, two math sections and the Test of Standard Written English) was also investigated, although those numbers did not differ substantially from total timing data.

The relationship between SAT test scores and the amount of time spent on the verbal and math section of the test was investigated as well. Results showed that physically disabled and visually impaired students who spent more time on the verbal sections of the SAT achieved lower verbal scores than those who spent less time, while the opposite was true for the verbal scores of hearing‐impaired and learning‐disabled students. However, for the math sections of the SAT, students in all disabled groups who spent more time tended to achieve higher math scores.
THE INTERACTION OF STUDENT MAJOR‐FIELD GROUP AND TEXT CONTENT IN TOEFL READING COMPREHENSION
Authors: Hale Gordon A.
Published: September 2014

In light of the current emphasis on English for specific purposes, it was hypothesized that a student's major‐field area interacts with the text content in determining performance on TOEFL reading passages. To assess this possibility, the present study examined performance on the reading passages in TOEFL® forms used in four operational test administrations.

The results supported the study's hypothesis, as students in the two key major‐field groups, the humanities/social sciences and the biological/physical sciences, performed significantly better on passages related to their own groups than on other passages, for three of the four test forms examined.

Although the hypothesized interaction was statistically significant for most of the test forms, however, the effect was relatively small, as expressed in terms of points on the TOEFL scale. Thus, a distinction must be drawn between the practical significance and the statistical significance of the interaction effect. Practically, the effect appears to be relatively small with typical TOEFL reading passages, perhaps because they are drawn from general readings rather than specialized textbooks. Statistically, however, the present results showed the effect to be a reliable phenomenon, even if relatively small in magnitude, thus supporting the theoretical view that a student's major‐field area interrelates with the text content in determining reading performance.
RELATIONSHIP BETWEEN ITEM CHARACTERISTICS AND AN INDEX OF DIFFERENTIAL ITEM FUNCTIONING (DIF) FOR THE FOUR GRE VERBAL ITEM TYPES
Authors: Freedle Roy , Kostin Irene
Published: September 2014

Two studies are reported. The first examined the factors that predict differences in item responses of two populations (Black and matched White examinees) to GRE analogies. Three factors were found to independently predict differential item responses of these two groups to 234 GRE analogy items: (1) item difficulty, (2) analogy stems with a part/whole relationship and (3) and analogy stems with an “attribute” relationship. An independent sample of 220 SAT analogy items was found to yield very similar results, especially for item difficulty and part/whole relationships. For both GRE and SAT analogies, Black examinees were found to do differentially better than matched White examinees on the hard analogy items.

Since item difficulty was found to be the most important predictor variable in Study I, Study II explored the possible importance of item difficulty as a predictor of differential item responses of Black versus matched White examinees for three other verbal item types of both the GRE and SAT tests (these types were antonyms, sentence completions, and reading comprehension items). Item difficulty was found to be an important predictor of the observed differences. An overview of the results suggests that the amount of verbal context might be an important determinant of the magnitude of the relationship between item difficulty and differential performance of Black versus matched White examinees. That is, analogies and antonyms (which have minimal verbal context) produced a stronger correlation of difficulty with differential ethnic performance than did sentence completion and reading comprehension items. This was found for both the GRE and SAT verbal item types. Several hypotheses are advanced to account for some of the observed ethnic differences.
AN ANALYSIS OF TEST WRITERS' EXPERTISE: MODELING ANALOGY ITEM DIFFICULTY
Authors: Enright Mary K. , Bejar Isaac I.
Published: September 2014

In this study, the ability of test development staff to predict the difficulty of analogy items was explored. The nature of the item attributes that contributed to test writers' predictions of difficulty as well as actual item difficulty was also investigated. The expert test writers studied were quite good at predicting item difficulty. Item attributes such as vocabulary difficulty and rationale difficulty contributed to item difficulty. However, a statistical model of item difficulty did not capture all the information that test writers used to judge item difficulty. This research contributes to the construct validation of tests in two ways. First, identification of some item attributes that are associated with item difficulty clarifies what skills and processes are likely to be involved in solving analogies. Secondly, the expertise of test writers, a crucial ingredient in ensuring the validity of the test, is demonstrated.
AN EXAMINATION OF THE RELATIONSHIPS OF ACADEMIC COURSEWORK WITH ADMISSIONS TEST PERFORMANCE
Authors: Morgan Rick
Published: September 2014

The redesigned Student Descriptive Questionnaire (SDQ) provides a great deal of background information about examinees sitting for the Scholastic Aptitude Test (SAT). One set of questions focuses on the number of years and types of courses in the students' academic background. This information makes it possible to explore the relationships between coursework and performance on the SAT. This study used data from the 1987 National Sample Tape, which contains SDQ responses and score information from 100,000 seniors in the class of 1987. The analyses examined the relationships between both the Admissions Testing Program (ATP) SAT and Achievement Test scores and the type and level of coursework in six academic areas. In order to provide a more accurate representation of these relationships, the data were adjusted to account for differences related to student academic achievement. The results show that coursework in the disciplines of mathematics, natural science, and foreign languages has the strongest adjusted relationships with SAT‐mathematical scores. SAT‐verbal scores appear to be most strongly related to the number of years of foreign language coursework. These relationships are generally consistent across ethnic groups and income levels. However, it appears that the relationships are stronger for students with higher grade‐point averages. The specific courses that seem to be most strongly related to SAT performance are upper‐level courses in mathematics, natural science, and foreign languages. The specific course relationships appear stronger for male than for female examinees. An analysis of Achievement Test data again indicates that upper‐level coursework in the three previously mentioned academic areas is most strongly related to performance on the Achievement Tests. All the research findings must be qualified because the study was exploratory. Student participation in the various courses was based solely on the motivation and the opportunity of the students to take the courses. As a result of this self‐selection, causal interpretations of the results are not appropriate.
ACCOUNTING FOR RANDOM RESPONDING AT THE END OF THE TEST IN ASSESSING SPEEDEDNESS ON THE TEST OF ENGLISH AS A FOREIGN LANGUAGE
Authors: Secolsky Charles
Published: September 2014

The usual assessment of speededness for rights‐only scored tests such as the Test of English as a Foreign Language (TOEFL) does not account for the possibility that examinees respond in a random or patterned fashion to the items at the end of the test as the time limit approaches. Therefore, for TOEFL, speededness measures that are based only on the number of items not reached may underestimate the degree to which the test is actually speeded.

The present study represented an attempt to determine if Sections 2 and 3 of TOEFL are truly speeded according to established criteria. Two exploratory techniques employing regression analyses were used in an attempt to account for the possibility that examinees responded randomly or in a patterned fashion to unconsidered items at the end of each section. One technique provided an estimate of the degree to which all examinees truly reached the 75 percent point on the sections. The second technique provided an estimate of the degree to which examinees truly completed the last set of items. Support for the results was obtained from an examination of the number of items not reached and the number of items at the end of the sections to which examinees responded in a patterned fashion. The findings are limited to the extent that one can attribute items not reached and patterned responding to the effect of speededness.

Four administrations of TOEFL were studied: two non‐pretest administrations and two longer pretest administrations. The results suggest that Section 3 for pretest administrations may be slightly speeded. It is recommended that more observational or survey methods be used to confirm this finding. If the finding is confirmed, it would be recommended that the TOEFL program investigate ways to increase the amount of time allotted per item.
Novel and Efficient Synthesis of DHPMs Catalyzed by di‐DACH‐Pyridylamide Ligands
Authors: Song Qingbao , An Xiaoxia , Che Fengfeng , Shen Tianhua
Published: September 2014

Di‐DACH‐pyridylamide ligands, symmetrical bridged bis‐Schiff base, and spiro pyrrolizines as catalysts in the synthesis of dihydropyrimidinethiones (DHPMs) using the Biginelli reaction is first reported. This new protocol has the advantages of environmental friendliness, short reaction time, excellent yields, and simple post‐treatment procedure. A series of DHPMs were obtained in high yields (up to 98%) in only 6 h. Moreover, based on the optimized condition, a novel Biginelli‐like reaction was first developed.
The feasibility and benefits of using volumetric arc therapy in patients with brain metastases: a systematic review
Authors: Andrevska Adriana , Knight Kellie A. , Sale Charlotte A.
Published: September 2014

Introduction

Radiotherapy management of patients with brain metastases most commonly involve a whole‐brain radiation therapy (WBRT) regime, as well as newer techniques such as stereotactic radiosurgery (SRS) and intensity modulated radiotherapy (IMRT). The long treatment times incurred by these techniques indicates the need for a novel technique that has shorter treatment times, whilst still producing highly conformal treatment with the potential to deliver escalated doses to the target area. Volumetric modulated arc therapy (VMAT) is a dynamic, highly conformal technique that may deliver high doses of radiation through a single gantry arc and reduce overall treatment times. The aim of this systematic review is to determine the feasibility and benefits of VMAT treatment in regard to overall survival rates and local control in patients with brain metastases, in comparison with patients treated with WBRT, SRS and IMRT.

Methods

A search of the literature identified 23 articles for the purpose of this review. Articles were included on the basis they were human‐based studies, with sample sizes of more than five patients who were receiving treatment for 1–10 metastatic brain lesions.

Results

VMAT was found to be highly conformal, have a reduced treatment delivery time and incurred no significant toxicities in comparison with WBRT, SRS and IMRT.

Conclusion

Compared to other treatment techniques, VMAT proved to have fewer toxicities than conventional WBRT, shorter treatment times than SRS and similar dose distributions to IMRT plans. Future prospective studies are needed to accurately assess the prognostic benefits of VMAT as well as the occurrence of late toxicities.
Biochar application to soil for climate change mitigation by soil organic carbon sequestration
Authors: Lorenz Klaus , Lal Rattan
Published: September 2014

Pyrogenic carbon (C) is produced by incomplete combustion of fuels including organic matter (OM). Certain ranges in the combustion continuum are termed ‘black carbon' (BC). Because of its assumed persistence, surface soils in large parts of the world contain BC with up to 80% of surface soil organic C (SOC) stocks and up to 32% of subsoil SOC in agricultural soils consisting of BC. High SOC stocks and high levels of soil fertility in some ancient soils containing charcoal (e.g., terra preta de Índio) have recently been used as strategies for soil applications of biochar, an engineered BC material similar to charcoal but with the purposeful use as a soil conditioner (1) to mitigate increases in atmospheric carbon dioxide (CO2) by SOC sequestration and (2) to enhance soil fertility. However, effects of biochar on soils and crop productivity cannot be generalized as they are biochar‐, plant‐ and site‐specific. For example, the largest potential increases in crop yields were reported in areas with highly weathered soils, such as those characterizing much of the humid tropics. Soils of high inherent fertility, characterizing much of the world's important agricultural areas, appear to be less likely to benefit from biochar. It has been hypothesized that both liming and aggregating/moistening effects of biochar improved crop productivity. Meta‐analyses of biochar effects on SOC sequestration have not yet been reported. To effectively mitigate climate change by SOC sequestration, a net removal of C and storage in soil relative to atmospheric CO2 must occur and persist for several hundred years to a few millennia. At deeper soil depths, SOC is characterized by long turnover times, enhanced stabilization, and less vulnerability to loss by decomposition and erosion. In fact, some studies have reported preferential long‐term accumulation of BC at deeper depths. Thus, it is hypothesized that surface applied biochar‐C (1) must be translocated to subsoil layers and (2) result in deepening of SOC distribution for a notable contribution to climate change mitigation. Detailed studies are needed to understand how surface‐applied biochar can move to deeper soil depths, and how its application affects organic C input to deeper soil depths. Based on this knowledge, biochar systems for climate change mitigation through SOC sequestration can be designed. It is critically important to identify mechanisms underlying the sometimes observed negative effects of biochar application on biomass, yield and SOC as biochar may persist in soils for long periods of time as well as the impacts on downstream environments and the net climate impact when biochar particles become airborne.
PseDNA‐Pro: DNA‐Binding Protein Identification by Combining Chou’s PseAAC and Physicochemical Distance Transformation
Authors: Liu Bin , Xu Jinghao , Fan Shixi , Xu Ruifeng , Zhou Jiyun , Wang Xiaolong
Published: September 2014

Identification of DNA‐binding proteins is an important problem in biomedical research as DNA‐binding proteins are crucial for various cellular processes. Currently, the machine learning methods achieve the‐state‐of‐the‐art performance with different features. A key step to improve the performance of these methods is to find a suitable representation of proteins. In this study, we proposed a feature vector composed of three kinds of sequence‐based features, including overall amino acid composition, pseudo amino acid composition (PseAAC) proposed by Chou and physicochemical distance transformation. These features not only consider the sequence composition of proteins, but also incorporate the sequence‐order information of amino acids in proteins. The feature vectors were fed into Support Vector Machine (SVM) for DNA‐binding protein identification. The proposed method is called PseDNA‐Pro. Experiments on stringent benchmark datasets and independent test datasets by using the Jackknife test showed that PseDNA‐Pro can achieve an accuracy of higher than 80 %, outperforming several state‐of‐the‐art methods, including DNAbinder, DNA‐Prot, and iDNA‐Prot. These results indicate that the combination of various features for DNA‐binding protein prediction is a suitable approach, and the sequence‐order information among residues in proteins is relative for discrimination. For practical applications, a web‐server of PseDNA‐Pro was established, which is available from http://bioinformatics.hitsz.edu.cn/PseDNA‐Pro/.
Complex UWB pulse generator based on nonlinear PM‐IM conversion
Authors: Yang Chengliang , Xia Li , Xu Jun , Liu Deming
Published: September 2014

We propose a simple approach to generate complex ultrawideband (UWB) pulse signal. The proposed system consists of a tunable laser source, phase modulator, an optical bandpasss filter, and photodetector. The light source is phase‐modulated by an electrical Gaussian pulse train via phase modulator. The UWB pulses are generated in the process of nonlinear phase modulation to intensity modulation conversion, equal to a high‐pass microwave photonic filter in frequency domain. By locating the carrier at different position, UWB pulses with different shape and frequency components are obtained. Experimental measurements in both time and frequency domains are presented. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2780–2784, 2014
Implementation of electronic beam steering system using look‐up table calibration method
Authors: Jang Sung‐hoon , Kim Jong‐phil , Kim Seon‐joo , Cheon Chang‐yul
Published: September 2014

This article presents a design and implementation of the electronically beam steering system for active electronically scanning array (AESA) radar. This beam steering system used look‐up table (LUT) calibration method to calibrate an amplitude and phase errors of each T/R Modules. LUT contains the T/R Module characterization data and the antenna correction data. Performance of this beam steering system was verified with the X‐band AESA radar demonstrator which has 1024 radiating elements and 504 T/R Modules. Beam steering angle is ±60° in each azimuth and elevation. Beam steering time is 3 µs using the precalculation method of the next steering position. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2769–2773, 2014
Method to sensitize an arc‐induced LPFG‐based sensor using double‐pass configuration
Authors: Loh Mey C. , Rahman Faidz A. , Kuramitz Hideki , Yong Yun T.
Published: September 2014

The sensitivity of the arc‐induced long period fiber grating (LPFG) sensor was improved utilizing the double‐pass configuration. The sensitivity in terms of transmission attenuation of the resonance wavelength for the double‐pass LPFG configuration was better compared to the single‐pass configuration when it was used to monitor the avidin–biotin interaction over a period of 60 min. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2766–2769, 2014
Protein immobilization onto IPA interface with optical fiber sensor based on surface plasmon resonance
Authors: Chen Liang‐Yu , Tsao Yu‐Chia , Lin Yu‐Cheng
Published: September 2014

Surface plasmon resonance (SPR) optical fiber sensing technology is applied to monitor the immobilization of globular protein (globular bovine serum albumin) onto the material surface and kinetic mechanism of protein adsorption is proposed for isopropanol (IPA) interface according to the correlation between the resonance wavelength shift and SPR efficiency. Furthermore, the optical fiber SPR technique would be applied for clinical testing and diagnostics. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2826–2828, 2014
Experimental verification of tunable property of a zeroth‐order resonator on ferrite substrate
Authors: Zermane Aziza , Sauviac Bruno , Bayard Bernard , Payet‐Gervy Beatrice , Rousseau Jean Jaques , Benghalia Abdelmadjid
Published: September 2014

This article presents a composite right–left‐handed (CLRH) zeroth‐order resonator designed on a ferrite substrate. Numerical modelling and measurements of the device are presented. The proposed structure is realized in coplanar waveguide configuration using an interdigital capacitor and a shortcircuited stub inductor to add the left‐handed property to the resonator. The ferrite substrate is magnetized in a direction perpendicular to the propagation direction. The tunable nature of the proposed device can be achieved by changing the applied magnetic bias. The resonator is designed to be tuned over the 3–5 GHz frequency band. Measured insertion loss is 5 dB giving interesting perspectives for the device. The length of the proposed device is 5.2 mm, which can be considered very small compared with a traditional half wave resonator. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2805–2809, 2014
Mm‐wave imaging results based on a frequency scanning delay line waveguide horn antenna array
Authors: Larumbe‐Gonzalo Belén , Ibáñez‐Loinaz Asier , Gonzalo Ramón , Teniente Jorge
Published: September 2014

First experimental mm‐wave imaging results, acquired with a frequency scanning horn antenna array, are presented. The antenna achieves a circular pattern that scans more than 30° in the E‐plane. Images acquired with this configuration are presented, demonstrating the benefits of these kinds of frequency scanning antennas for reduced cost imaging applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2851–2860, 2014
A solar‐powered 2.4‐GHz CMOS VCO
Authors: Wu Jian‐Ming , Chuang Ching‐Jui
Published: September 2014

A solar‐powered 2.4‐GHz voltage‐controlled oscillator (VCO) is developed using an energy harvesting technique. The main feature of the VCO is self‐powered by a solar panel with an adjustable voltage regulator circuit which directly converts solar power to the electrical power. The presented VCO design is based on an NMOS‐only cross‐coupled pair with an integrated LC tank. The capacitor and varactor in this LC tank are the intrinsic junction capacitors of NMOS transistors. The VCO is implemented using the TSMC 0.18 µm CMOS standard process. Measurements of the solar‐powered VCO are made, revealing that the output power is −17.46 dBm; the phase noise is −116.87 dBc/Hz at a 1 MHz offset, and the frequency tuning range is 3.4 %. The supply voltage that is applied to VCO is only 0.5 V with a power consumption of 1.25 mW. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2874–2878, 2014
Compact microstrip bandpass filter with fragment‐loaded resonators
Authors: Zhao Qi , Wang Gang , Ding Dawei
Published: September 2014

Microstrip bandpass filter with fragment‐loaded resonators is proposed and designed using multiobjective evolutionary algorithm based on decomposition combined with enhanced genetic operators (MOEA/D‐GO). When loaded by fragment‐type structures, microstrip resonators may have compact size and operate at different modes. By properly setting the modes of fragment‐loaded resonators in objectives of MOEA/D‐GO, stopband attenuation and spurious passband suppression of the microstrip bandpass filter can be readily adjusted and controlled. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2896–2899, 2014
A frequency reconfigurable planar inverted‐F antenna for WWAN mobile handset applications
Authors: Lee S. W. , Sung Y. J.
Published: September 2014

In this article, a reconfigurable antenna for wireless wide area network (WWAN) mobile handset application is proposed. The proposed antenna consists of a conventional planar inverted‐F antenna (PIFA), parasitic line, PIN diode, and bias line. The PIN diode is located between the parasitic line and ground, and its connection is electrically controlled by the on/off state of the PIN diode. The antenna's wide low band is formed by switching the quarter‐wavelength resonance mode of a conventional PIFA and covers the GSM850/900 bands. The antenna's high band is formed by the harmonic mode of a conventional PIFA and a new generated loop mode and covers the GSM1800/1900/UMTS bands. A stable and omnidirectional radiation pattern with a reasonable gain is observed over the operating bandwidth. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2888–2893, 2014
Design and implementation of a novel dual band notched antenna for UWB applications
Authors: Zou Yanlin , Zhao Xiaoping , Fang Wei , Sun Baohua
Published: September 2014

A novel dual band‐notched antenna with simple structure for ultrawideband (UWB) applications is presented in this letter. The proposed antenna is a broadband printed monopole antenna, consisting of a hexagonal radiation patch and a rectangular ground plane with an etched circular area below the patch. By inserting two pairs of symmetric L‐shaped parasitic branches into the etched circular area, dual notch bands are achieved, respectively, at the WiMAX and WLAN band. The proposed antenna is small in size (30 × 40 mm2) and operates at the band from 2.2 to 12 GHz for VSWR < 2, except for 2.7–3.7 and 4.9–6.0 GHz. A prototype of the antenna is fabricated and measured. The simulated and measured results indicate the antenna has a good prospect for UWB applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2922–2925, 2014
A tapered double cross patch antenna for dual‐band monopole‐like radiation
Authors: Tak Jinpil , Kang Do‐Gu , Choi Jaehoon
Published: September 2014

A low‐profile tapered double cross patch antenna (TDCPA) with dual‐band monopole‐like radiation characteristic is proposed. The proposed TDCPA consists of a center‐fed circular patch on the middle layer to excite a TM01 mode and a double cross patch on the top layer to generate the dual‐band characteristic. The antenna has monopole‐like radiation in the industrial, scientific, and medical (ISM) 2.45 GHz band and ISM 5.8 GHz band. The corresponding fractional 10‐dB return loss bandwidths and maximum gains are 3.67% and 4.5 dBi for the lower frequency band and 14.7% and 6.5 dBi for the higher frequency band, respectively. The antenna has only 0.038 λ0 thickness. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2929–2933, 2014
A broadband dumbbell‐shaped dielectric resonator antenna
Authors: Chaudhary Raghvendra Kumar , Srivastava Kumar Vaibhav , Biswas Animesh
Published: September 2014

In this article, a dumbbell‐shaped dielectric resonator antenna (DRA) fed by coaxial probe is proposed for wideband applications. The proposed dumbbell‐shaped DRA can be achieved by three‐layer structure of same material where the radius of middle cylinder is smaller than the top and bottom disc. In dumbbell‐shaped DRA, the effective permittivity varies in both axial and radial direction. A complex hybrid mode similar to HE11δ mode is excited through a coaxial probe. The proposed dumbbell‐shaped DRA provides the measured impedance bandwidth of 57.59% (at resonance frequency of 4.48 GHz) from 4.11 to 6.69 GHz for input reflection coefficient (S11) less than −10 dB. The simulated and measured radiation patterns are consistent throughout the operational bandwidth. The average measured gain of proposed antenna is 4.88 dB in the frequency range of 4.11–6.69 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2944–2947, 2014
Compact lowpass filter with high suppression level and wide stopband using stepped impedance m‐shape units
Authors: Du Zebao , Yang Hao , Zhang Haiying , Zhu Min
Published: September 2014

A lowpass filter (LPF) with high suppression level and wide stopband using novel stepped‐impedance m‐shape unit is presented. The low impedance section of center‐loaded stepped‐ impedance resonator is implemented using T‐shape open stub with three arms, which improve design freedom and reduce size simultaneously. The mechanism for rejection level and stopband width is analyzed based on one stepped‐impedance m‐shape unit. The implemented filter composed with three different unit exhibits 40‐dB rejection from 1.4 fc to 7.2 fc, where fc is 3‐dB cutoff frequency. The compact size of the cascaded LPF is as small as 0.25 λg × 0.08 λg, where λg is guided wavelength at cutoff frequency. The measured results show good agreement according with simulated ones. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2947–2950, 2014
Loss effect analysis in optical delay lines based on two coupled resonators
Authors: Le Duykhanh , Tran Thang Q. , Kim Sangin
Published: September 2014

A general analysis on loss effect on performances of coupled resonator‐based optical delay lines is presented. Two types of the coupled resonators are considered: an electromagnetically induced transparency‐like resonance and an all‐pass filter. Our analysis reveals that the all‐pass filter type is much more tolerant of the resonator loss. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2984–2987, 2014
Tailoring of higher‐order mode suppression in a high‐power alternative to classical waffle‐iron filters
Authors: Teberio Fernando , Arregui Iván , Arnedo Israel , Chudzik Magdalena , Jost Rolf , Görtz Franz‐Josef , Lopetegi Txema , Laso Miguel A. G.
Published: September 2014

In this article, a novel stepwise technique for the design of high‐power low‐pass harmonic filters is proposed. The fundamental and higher‐order mode suppression process is divided into three different steps. In the first step, the fundamental TE10‐mode rejected band is accomplished by adjusting the height of E‐plane bandstop elements along the propagation direction. In the second step, this arrangement of bandstop elements is made two‐dimensional to suppress the higher‐order TEn0 modes. Finally, the higher‐order non‐TEn0 modes are rejected by controlling the minimum mechanical gap of the filter. The design process ends after the first, second, or third step depending on the intended mode behavior for the filter. The main characteristic of the new design technique is that the filter minimum mechanical gap can always be made much larger than in the classical solution (E‐plane corrugated or waffle‐iron filters) for the same frequency specifications. To validate the control of the higher‐order mode suppression that this method permits, three different filters are designed and compared. Moreover, a prototype has been fabricated and its S‐parameters measured to prove the feasibility of the proposed filters for a tailored frequency response. Finally, its high‐power handling capability has been estimated. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2967–2974, 2014
Aperture slot size effect to wide band open air gap radial‐line slot array performance
Authors: Ibrahim I. M. , Rahman T. A. , Iliya S. Z. , Sabran M. I.
Published: September 2014

A wideband open air gap radial line slot array (RLSA) antenna is presented for point‐to‐point application. This article investigates the optimum slot arrangement and the effect of slot width to the RLSA antenna. Eight models were developed and simulated with slot width taking range in values from 1 to 8 mm. Results from simulation shows optimum performance at 6‐mm slot width. The 2‐mm slot width gave similar performance to the 6‐mm slot width in term of gain and directivity. Both antennas were fabricated and measured, from the measurement; a better return loss performance of about 28% was realized at 6‐mm slot width when compared to 2‐mm slot width RLSA. However, both antennas produced the same gain. A better sidelobe level of 2.9 dB was achieved with the 2‐mm slot width antenna. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2974–2978, 2014
Improved diffusion tensor imaging of the optic nerve using multishot two‐dimensional navigated acquisitions
Authors: Jeong Ha‐Kyu , Dewey Blake E. , Hirtle Jane A.T. , Lavin Patrick , Sriram Subramaniam , Pawate Siddharama , Gore John C. , Anderson Adam W. , Kang Hakmook , Smith Seth A.
Published: September 2014

Purpose

A diffusion‐weighted multishot echo‐planar imaging approach combined with SENSE and a two‐dimensional (2D) navigated motion correction was investigated as an alternative to conventional single‐shot counterpart to obtain optic nerve images at higher spatial resolution with reduced artifacts.

Methods

Fifteen healthy subjects were enrolled in the study. Six of these subjects underwent a repeated acquisition at least 2 weeks after the initial scan session to address reproducibility. Both single‐shot and multishot diffusion tensor imaging studies of the human optic nerve were performed with matched scan time. Effect of subject motions were corrected using 2D phase navigator during multishot image reconstruction. Tensor‐derived indices from proposed multishot were compared against conventional single‐shot approach. Image resolution difference, right–left optic nerve asymmetry, and test–retest reproducibility were also assessed.

Results

In vivo results of acquired multishot images and quantitative maps of diffusion properties of the optic nerve showed significantly reduced image artifacts (e.g., distortions and blurring), and the derived diffusion indices were comparable to those from other studies. Single‐shot scans presented larger variability between right and left optic nerves than multishot scans. Multishot scans also presented smaller variations across scans at different time points when compared with single‐shot counterparts.

Conclusion

The multishot technique has considerable potential for providing improved information on optic nerve pathology and may also be translated to higher fields. Magn Reson Med 74:953–963, 2015. © 2014 Wiley Periodicals, Inc.
A novel method to attain sinusoidal mechanical responses from single motor units
Authors: Gobbo Massimiliano , Celichowski Jan , Krutki Piotr , Drzymała‐Celichowska Hanna , Solomonow Moshe , Orizio Claudio
Published: September 2014

Introduction: The relationship between output force and motor command depends on the intrinsic dynamic responses of motor units (MUs), which can be characterized by evoking accurate sinusoidal force responses at different frequencies. In this study we sought to determine whether sinusoidal modulation of the stimulation rate of single MUs results in reliable sinusoidal force changes. Methods: Single axons of rat ventral roots were stimulated electrically by changing the pulse rate sinusoidally at different frequency modulation (0.4–1.0–2.0–4.0 Hz for slow, 1.0–2.0–4.0–7.0 Hz for fast MUs). The twitching sinusoidal force signal was interpolated. We calculated harmonic distortion (HD) and the correlation coefficient (r) between theoretical sines and interpolated signals. Results: HD was always <5%, and r was always >0.97. Conclusions: The HD and r‐values obtained indicate highly reliable sinusoidal responses, which supports the potential use of this method to further characterize the dynamic behavior of single MUs. Muscle Nerve 51: 134–136, 2015