bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a high‐speed laser interferometer using an acousto‐optic deflector
Authors: Fukuchi Tetsuo , Nayuki Takuya , Nemoto Koshichi , Uchino Kiichiro
Published: May 2004

An acousto‐optic laser deflector was used as a shutter for high‐speed imaging of laser interference fringes using an ordinary CCD camera. The exposure duration was set by the pulse width of the high‐frequency signal applied to the acousto‐optic deflector. Changes in laser interference fringes due to an impulse discharge in air were obtained at an exposure duration of 4 µs. By applying a sequence of high‐frequency signals with different frequency, the beam was deflected to four different angles at different times, allowing four interference images to be captured on a single video frame. This was used for time‐resolved imaging of the interference fringe pattern. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 76–83, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20011
Enantioselective Recognition of Amino Acid by Differential Pulse Voltammetry in Molecularly Imprinted Monolayers Assembled on Au Electrodes
Authors: Huan Shuangyan , Shen Guoli , Yu Ruqin
Published: May 2004

An electrochemical sensor based on L‐cysteine SAM imprinted by L‐serine has been developed for the detection of L‐serine. The sensor shows some entantioselectivity toward L‐serine and a stable response establishes within 5 min. The peak current intensity of potassium ferricyanide quantified by differential pulse voltammetry (DPV) decreased linearly with increasing L‐serine concentration from 10 to 100 μM with a gradient of 20.91 nA μM−1. The detection limit was 4.32 μM. The coefficient of enantiometric selectivity of the molecularly imprinted SAM was about 3.0. Compounds with similar structure as serine caused much less response.
A Novel Sulfate Polymeric Membrane Sensor Based on a New Bis‐Pyrylium Derivative
Authors: Ganjali Mohammad Reza , Shirvani‐Arani Simindokht , Nourozi Parviz , Salimzadeh Davood , Faal‐Rastegar Madjid , Moghimi Abolghasem
Published: May 2004

A novel ion‐selective polymeric membrane sensor based on pyrylium‐4,4‐(1,4‐phenylen) bis[2,6‐bis(2‐naphthyl)]‐bis[tetrafluoroborate] (PBGNB) as an excellent sensing material is successfully developed. The electrode possesses the advantages of a very low detection limit (5.0×10−8 M), a wide working concentration range (1.0×10−8−1.0×10−1 M) and specially, a high sulfate selectivity over most common organic and inorganic anions. The sensor displays Nernstian behavior (slope of 29.5±0.5 mV per decade) in a wide pH range (3.0–8.5). It shows a short response time in the whole concentration range (ca. 10 s). The electrode was used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions. The proposed sensor was successfully applied to the direct determination of salbutamol sulfate and paromomycin sulfate.
Effects of hydrogen peroxide on light emission by various strains of marine luminescent bacteria
Authors: Katsev Andrey M. , Węgrzyn Grzegorz , Szpilewska Hanna
Published: May 2004

Light‐emitting bacteria are the most abundant and widespread luminescent organisms. Most species of such bacteria live in marine environments. However, until recently, biological role of bacterial luminescence remained unknown. Recent studies indicated that light produced in bacterial cells may stimulate DNA repair. Therefore, it is not surprising that agents that cause DNA damage induce expression of lux genes. Moreover, it was proposed previously that bacterial luciferases may be involved in detoxification of reactive oxygen species. Recently, this hypothesis was confirmed experimentally. Here we investigated effects of hydrogen peroxide on light emission by various strains of luminescent bacteria. We found that luminescence of strains with luciferase of fast kinetics of reaction decreased at considerably lower concentrations of H2O2 than that of strains with luciferase of the slow kinetics. The action (either direct or indirect) of luciferases as anti‐oxidants seemed to be independent of activity of catalase, which was found to be different in various strains. Therefore, it seems that luciferases of the slow kinetics are more efficient in detoxification of reactive oxygen species than those of the fast kinetics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cytosolic NADP phosphatases I and II from Arthrobacter sp. strain KM: Implication in regulation of NAD+/NADP+ balance
Authors: Kawai Shigeyuki , Mori Shigetarou , Mukai Takako , Murata Kousaku
Published: May 2004

NADP phosphatase (NADPase) is an enzyme that converts NADP+ into NAD+ through dephosphorylation of NADP+, and is considered to be one of the possible candidates for regulation of the NAD+/NADP+ balance in vivo. In order to obtain an intrinsic NADPase, the NADP+‐degrading activity in a membrane‐free cell extract of a Gram‐positive bacterium, Arthrobacter sp. strain KM, was first assessed and demonstrated to be mainly achieved through the NADPase reaction, indicating NADPase is essential for degradation of NADP+ and therefore for regulation of the NAD+/NADP+ balance in cytosol. Then, the isolation of cytosolic NADPase was attempted using NADP+ as a substrate. Two NADPase isozymes, designated as NADPases I and II, were purified from the cell extract of the bacterium, and were indicated to be the sole cytosolic NADPases regulating the balance of NAD+/NADP+. NADPases I and II are homodimers of 32 and 30 kDa subunits, respectively, and most active at pH 7–8. The N‐terminal amino acid sequences of the two enzymes are similar to each other. Among the biological substrates tested, both enzymes showed the highest activity toward NADP+ and NADPH. AMP, ADP, and pyridoxal 5′‐phosphate were also dephosphorylated, but to lower extents. Comparison of the features of NADPases I and II with those of other acid phosphatases possessing NADPase activity suggested that NADPases I and II are novel enzymes participating in regulation of the NAD+/NADP+ balance in the cytosol. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of three new culture media for the cultivation and isolation of Leishmania parasites
Authors: Limoncu Me. , Özbilgin A. , Balcioḡlu İc. , Özbel Y.
Published: May 2004

The aim of this study was to establish novel culture media for Leishmania parasites with a potential of obtaining hight amounts of promastigotes with long‐term viability, and consisting of ingredients that were available in microbiology or parasitology laboratories. Other features of these media included no requirement for blood, FCS (Fetal calf serum) or erythrocyte lysate, inexpensiveness and easiness in preparation. In addition, aspiration samples obtained from cutaneous leishmaniasis (CL) suspected patients were cultivated in these media.

Three culture media were prepared; trypticase beef extract hemoglobine (TBH) medium, including trypticase, beef extract and yeast extract as the protein source, glucose as the carbohydrate source, FeNH4 and bovine hemoglobine; Peptone‐Yeast extract medium (PY), found to be effective in our previous studies for cultuvation of on Leishmania parasites, with bovine hemoglobine (PYH) and Brain Heart medium, containing bovine hemoglobine (BKH).

The number of promastigotes were the highest on day 8 and 13 in RPMI 1640 and BKH medium, respectively. In TBH and PYH, the peak level of reproduction was between day 16 and 19, and it was found to be higher in TBH medium after the day 20. The number of promastigotes were found to be close in BKH, TBH and RPMI‐1640 media and lower in PYH medium.

Examination of the cultivation of the aqueous lesion specimens of the 10 CL‐suspected cases in media revealed reproduction in 9 flasks of RPMI‐1640 containing 10% FCS, 7 TBH, 6 BKH and 4 PYH. The differences between the culture media were not found to be statistically significant.

These results suggested that, three liquid culture media, assessed in this study, with no requirement for FCS or erythrocyte lysate, were effective in the reproduction of promastigotes, and could be used effectively in the patient isolation and field studies, as well. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of pyrimidine biosynthesis in “Pseudomonas alkanolytica” ATCC 21034
Authors: West Thomas P.
Published: May 2004

The control of de novo pyrimidine biosynthesis in the industrially important patent strain “Pseudomonas alkanolytica” ATCC 21034 was investigated. Uracil supplementation of succinate‐grown “P. alkanolytica” cells produced the greatest depression of the de novo pyrimidine biosynthetic pathway enzyme activities. After the pyrimidine limitation of a “P. alkanolytica” orotate phosphoribosyltransferase mutant strain grown on succinate, the pyrimidine biosynthetic pathway enzyme activities were derepressed. The pyrimidine biosynthetic pathway enzyme aspartate transcarbamoylase in “P. alkanolytica” was inhibited by pyrophosphate, cytidine 5′‐triphosphate (CTP), uridine 5′‐triphosphate (UTP), and guanosine 5′‐triphosphate (GTP). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of Polypyrrole Microtubes with Actinomorphic Morphology in the Presence of a β‐Cyclodextrin Derivative‐Methyl Orange Inclusion Complex
Authors: Hu Xueqing , Lu Yun , Liu Jinhui
Published: May 2004

Summary: Polypyrrole (PPy) microtubes with an actinomorphic morphology are synthesized by a chemical method in the presence of an inclusion complex (IC) of mono [6‐deoxy‐6‐(2‐butenedinitrile‐2,3‐dimercapto sodium salt)]‐β‐cyclodextrin (6‐mnt‐β‐CD) with methyl orange (MO) as a dopant in aqueous solution. The morphologies of the obtained PPy were studied using transmission electron microscopy (TEM). It was found that the IC of 6‐mnt‐β‐CD with MO significantly affects the morphology of the resulting PPy.

The morphology of polypyrrole synthesized in the presence of 6‐mnt‐β‐CD/MO, determined by TEM.

image

The morphology of polypyrrole synthesized in the presence of 6‐mnt‐β‐CD/MO, determined by TEM.
Poly[(3,3′‐dimethyl‐1,1′‐biphenyl‐4,4′‐diyl)ethynediyl(2,5‐dioctyl‐1,4‐phenylene)ethynediyl] and a related copolymer – new blue EL polymers
Authors: Joo Sung‐Hoon , Jin Jung‐Il
Published: May 2004

Electroluminescence (EL) properties of a new poly(aryleneethynylene) and a related copolymer were studied. They are poly[(3,3′‐dimethyl‐1,1′‐biphenyl‐4,4′‐diyl)ethynediyl(2,5‐dioctyl‐1,4‐phenylene)ethynediyl] (PPEBE) and related copolymer (PPEBE‐co‐mP) containing 20 mole % of 1,3‐phenylene units. Both polymers are blue‐light emitters; the former was found to perform better than the latter when the light‐emitting diode (LED) device had the configuration of ITO/PEDOT/polymer/Li:Al. The device constructed with the former polymer exhibited the external quantum efficiency of 0.05 and the maximum brightness higher than 400 cd/m2 with its EL spectrum showing maxima at λ = 445 and 472 nm. The performance of the device constructed with the copolymer was about one fifth of the device fabricated with the homopolymer.
Frequency analysis of diffusion in 1D systems with energy and spatial disorder
Authors: Pitarch Angeles , Garcia‐Belmonte Germà , Bisquert Juan
Published: May 2004

We have analyzed the frequency‐dependent features of diffusive transport of mobile carriers by hopping in a disordered environment composed of varying energy barriers. We developed a simple approach based on the solution of the master equation for a gradient of concentration (chemical potential) under a sinusoidal perturbation. This method extends the well‐known result of the steady state case, D = {1 / Γ}−1, to the frequency domain. The results of our calculations are in agreement with the approximate analytical solution of the CTRW formalism. We are able to determine the onset of frequency‐dependent diffusivity in terms of probabilities of highest energy barriers.
Quenching of exciplex and charge‐transfer complex fluorescence of poly(N‐vinylcarbazole) – benzanthrone system
Authors: Siegoczyński R.M. , Ejchart W.
Published: May 2004

When benzanthrone (Bt), a weak electron acceptor, is doped into poly(N‐vinylcarbazole) (PVCz) solution or film, an excited carbazole chromophore (D*) interacts with Bt to form a new exciplex state, which gives a broad fluorescence band (λmax = 440 nm) in solution and a new state, which gives broad fluorescence (λmax = 550 nm) in the film. In order to elucidate the origin of these new states, we have studied the results of experiments for absorption, concentration dependence of the excimer and exciplex fluorescence quenching, both in solution and in the film, and electric field‐induced fluorescence quenching in the film. Taking into account that (i) the new state formation in the PVCz film containing small amounts of Bt enhances the photocurrent in the absorption region, where the photon energy is insufficient to excite polymer molecules directly into the conduction state, (ii) the 550 nm fluorescence of the PVCz ‐ Bt system in film is only partly quenched by electric field, (iii) the appearance of structureless tail in the fluorescence excitation spectrum, the charge transfer interaction model of the PVCz ‐ Bt system in film is proposed.
Improved performance of EBGs on a co‐planar transmission line using tapered distribution
Authors: Padhi Shantanu Kumar
Published: May 2004

Conventional electromagnetic crystals or electromagnetic bandgaps (EBGs) with uniform distribution show spurious ripples in the pass band and poor stop‐band responses. This paper presents a detailed theoretical investigation of the performance of EBGs on a uniplanar transmission line using tapered distribution. The nonuniform size of the EBGs is used to improve the ripple height, 20‐dB rejection band, and selectivity of the filter over the pass‐band and stop‐band regions. The calculated S parameters exhibit significant improvement in ripple height and rejection bandwidth, as compared with the conventional EBG‐assisted coplanar transmission line. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 128–131, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20228
Resonant influence of small S‐shaped particles on the guided mode of a coplanar line
Authors: Verney E. , Rouiller T. , Simovski C. R. , Sauviac B. , Capraro S.
Published: May 2004

Artificial dielectrics prepared as planar grids appear to have potential use and applications at microwaves due to their easy fabrication and their wide range of obtainable properties. Here, we study a grid of metallic S‐particles introduced in the design of a coplanar waveguide and demonstrate the resonant influence of the grid to the S‐matrix of the coplanar waveguide. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 131–133, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20229
1.57‐μm InP‐based resonant‐cavity‐enhanced photodetector with InP/air‐gap Bragg reflectors
Authors: Ren Xiaomin , Huang Hui , Chong Yingzhe , Huang Yongqing
Published: May 2004

We have demonstrated a monolithic and cost‐effective InP‐based resonant‐cavity‐enhanced photodetector with an InP/air‐gap distributed Bragg reflector (DBR) fabricated by using selective wet etching. Peak quantum efficiency is 54% at 1.57 μm, which corresponds to nearly two‐fold enhancement versus a conventional detector of the same absorption depth, a 3‐dB bandwidth of 6.8 GHz was achieved with the active area of 50 × 50 μm2. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 133–135, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20230
Evaluation of the spatial distribution of birefringence in an optical‐fiber link
Authors: Perlicki K.
Published: May 2004

We present a simple method of the calculation of spatial distribution of birefringence in an optical‐fiber link. This method is based on an analysis of the properties of the backscattered optical signal. The analytical results are compared with the numerical results, and excellent agreement is obtained. We demonstrate that the spatial‐birefringence distribution may be obtained from the calculation of the roundtrip Muller matrices derived from only two power‐evolution traces, corresponding to two different angles of the polarizer. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 147–149, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20234
A novel dual‐band F‐inverted antenna printed on a PCMCIA card
Authors: Angelopoulos Evangelos S. , Kostaridis Antonis I. , Kaklamani Dimitra I.
Published: May 2004

This paper presents a novel dual‐band Inverted‐F Antenna (IFA) printed on a PCMCIA card. The antenna is based on the classic λ/4 printed IFA, which incorporates two individual monopoles separated by an L‐shaped slot that is properly optimized to achieve dual‐mode operation at 2.45 and 5.25 GHz. The antenna is aimed to support multiple wireless protocols, such as 802.11b and 802.11a. A prototype has been successfully developed and measured, while simulated and experimental results prove the favorable dual‐band characteristics of the printed antenna. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 153–156, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20236
2D full‐wave finite‐difference frequency‐domain method for lossy metal waveguide
Authors: Wang Bing‐Zhong , Wang Xiaohua , Shao Wei
Published: May 2004

The 2D finite‐difference frequency‐domain method combined with the surface‐impedance boundary condition is applied for the analysis of dispersion characteristics of lossy metal waveguides. Six electromagnetic field components are involved in the final eigen equation. By solving the eigen equation, the method finds the propagation constants for a given frequency. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 158–161, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20238
Low‐phase‐noise CMOS VCO with harmonically tuned LC tank
Authors: Chung Yujin , Lee Jong‐Ryul , Kim Bumman
Published: May 2004

A low‐phase‐noise voltage‐controlled oscillator (VCO) has been demonstrated using a harmonically tuned LC resonance tank. In this circuit configuration, the voltage shape at the differential cell is almost rectangular; thus, the cell is switched effectively and the phase noise is reduced. More importantly, the proposed tank suppresses down‐conversion of the noise around 2f0 to the phase noise, due to the 2nd harmonic short of the tank. Therefore, the phase noise of the VCO based on the tank is improved considerably. The VCO for 1‐GHz operation has been realized using a 0.35‐μm CMOS process. It shows a phase noise of −111.6 dBc/Hz at 100 KHz offset, which is a 5.7‐dB improvement over a comparable standard VCO. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 164–167, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20240
L‐strip excited wideband rectangular microstrip antenna
Authors: Lethakumary B. , Menon Sreedevi K. , Aanandan C. K. , Vasudevan K. , Mohanan P.
Published: May 2004

This paper presents the outcome of the experimental studies performed on L‐strip‐fed compact rectangular microstrip antenna. The effect of the feed parameters upon the characteristics of the antenna is studied in detail. The antenna offers an impedance bandwidth of nearly 20% and is suitable for broadband applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 173–175, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20243
Comparison study of pattern‐synthesis techniques using neural networks
Authors: Shavit R. , Taig I.
Published: May 2004

In this paper, a comparison study among three neural‐network algorithms for the synthesis of array patterns is presented. The neural networks are used to estimate the array elements' excitations for an arbitrary pattern. The architecture of the neural networks is discussed and simulation results are presented. Two new neural networks, based on radial basis functions (RBFs) and wavelet neural networks (WNNs), are introduced. The proposed networks offer a more efficient synthesis procedure, as compared to other available techniques. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 175–179, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20244
Prenatal screening for Down syndrome: the problem of recurrent false‐positives
Authors: Wald Nicholas J. , Huttly Wayne J. , Rudnicka Alicja R.
Published: May 2004

Objectives

It has been reported that, in prenatal screening programmes for Down syndrome, women who have false‐positive results in one pregnancy have an increased risk of a false‐positive result in a subsequent pregnancy. We examined the effect of this in the screening programme conducted from the Wolfson Institute of Preventive Medicine with a view to determining the magnitude of the effect, and to describe a method of avoiding the problem.

Methods

Six thousand four hundred and forty‐eight women were identified who had had two singleton pregnancies without Down syndrome in the screening programme based at the Wolfson Institute of Preventive Medicine, in which both pregnancies were screened using a Quadruple test (maternal age with alphafetoprotein (AFP), unconjugated oestriol (uE3), total or free β‐human chorionic gonadotrophin (hCG) and either free α‐hCG or inhibin‐A as the fourth serum marker).

Results

Among women who had a false‐positive result in their initial pregnancy, the false‐positive rate in the subsequent pregnancy was high: 20% (46/229), about three times higher than both the overall observed false‐positive rate (6.6%), and the expected false‐positive rate, in subsequent pregnancies that were false–positive in their initial pregnancy (7.5%) (p < 0.001). This arises because serum marker levels in one pregnancy are associated with the levels in a subsequent pregnancy. Using the slope (the regression coefficient b) of each marker level in a subsequent pregnancy regressed on the value in the first pregnancy, it is possible to adjust all marker values in a subsequent pregnancy to allow for the higher‐than‐expected false‐positive rate. This can be done by dividing the observed MoM value for each marker by the ‘expected’ MoM, which is the MoM value in a previous pregnancy raised to the power b.

Conclusions

If a woman has had a false‐positive result in one pregnancy, she is much more likely to have a false‐positive screening result in a subsequent pregnancy than women in general. The problem can be avoided by adjusting the serum markers in all women who have been screened in a previous pregnancy and who have not had a previous pregnancy with Down syndrome. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of thin polymer‐like films formed by plasma polymerization of methylmethacrylate: A neutron reflectivity study
Authors: Jeon H.S. , Wyatt J. , Harper‐Nixon D. , Weinkauf D.H.
Published: May 2004

The microstructure of the plasma‐polymerized methylmethacrylate (ppMMA) films is characterized using neutron reflectivity (NR) as a function of the plasma reaction time or film thickness. Variation in the crosslink density normal to the substrate surface is examined by swelling the film with a solvent, d‐nitrobenzene (dNB). In the presence of dNB, uniform swelling is observed throughout the bulk as well as at the air surface, and silicon oxide interfaces. The results indicate that the MMA film prepared by plasma polymerization (ppMMA) has a uniform crosslink density from air surface to substrate surface. Additionally, the scattering length density of the plasma‐polymerized MMA film (SLD ≈ 0.750 × 10−6 Å−2) is much lower than that of a conventional PMMA film (SLD = 1.177 × 10−6 Å−2). The increase in film thickness following dNB sorption is 7.5% and at least 36% for the ppMMA and PMMA films, respectively. This suggests that the films formed by plasma polymerization are different from conventional polymers in chemical structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2522–2530, 2004
Recognition of lung nodule shadows from chest X‐ray CT images using 3D Markov random field models
Authors: Takizawa Hotaka , Yamamoto Shinji , Nakagawa Tohru , Matsumoto Tohru , Tateno Yukio , Iinuma Takeshi , Matsumoto Mitsuomi
Published: May 2004

This paper presents a scheme for recognizing nodule shadows that are candidate lung cancer lesions from chest X‐ray CT images. In recognizing shadow candidates, their surrounding shadows give useful information. The proposed scheme recognizes nodule shadows by formulating the relationships between shadow candidates and their surrounding shadows in the framework of a three‐dimensional Markov random field model. First, it detects isolated shadows that become nodule candidates, extracts a volume of interest that includes shadow candidates, and divides the volume of interest into rectangular regions. It expresses nodules and blood vessels in three‐dimensional geometric models of spheres and cylinders, and lists a number of object models having high probabilities of existing in each rectangular region. It then generates a combination of object models by assembling the physical models. It formulates the relationships between each rectangular region, anatomical verifications of the object model combinations and the degree of agreement between observed CT images and object model combinations in the framework of a three‐dimensional Markov random field model, and computes the probability that a shadow candidate is a nodule and the probability that the shadow candidate is not a nodule. A shadow candidate is determined to be a nodule if the probability of it being a nodule is high, while it is determined to be normal otherwise. The proposed scheme is applied to actual CT images of 10‐mm slice intervals to show its efficacy. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(8): 82–95, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10453
Change of reaction time according to the presentation of cues about the direction of saccade in a delayed saccade task
Authors: Tsunoda Yoshiaki , Nakamura Kiyohiko
Published: May 2004

The preparation of saccade is examined on the basis of the reaction time in a delayed saccade task. The position of the visual stimulus presentation as the target of saccade is varied stochastically and then the signal indicating the start of the saccade is presented with a delay. In other words, a task is considered in which the direction of saccade is indicated before indicating the start of the saccade. We investigate how the preparation of the saccade progresses in the delay period following the indication of the direction. The following results were obtained in our experiments. (1) The reaction time decreases with increasing delay period. (2) The reaction time does not decrease but remains almost constant when the delay exceeds a certain value. (3) Even if the direction of saccade is known, the reaction time is decreased when the target is presented. As a conclusion, it is suggested that the saccade is prepared in the delay period based on the information concerning the saccade direction, since the reaction time decreases with increasing delay. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(8): 66–71, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10512
Odds ratios for a continuous outcome variable without dichotomizing
Authors: Moser Barry Kurt , Coombs Laura P.
Published: May 2004

The loss of information from dichotomizing a continuous outcome is well documented in the literature. One advantage of dichotomizing is that it allows estimation of odds ratio parameters through a logistic regression analysis. The objective of this paper is to develop a new estimator of the same odds ratio parameters through regression analysis on the original continuous outcome without the inherent loss of information caused by dichotomizing. Through a mathematical, asymptotic development the relative sample sizes required to attain a specified power when testing the odds ratio parameter are compared for the dichotomizing procedure and the proposed approach. The comparison highlights the substantial sample size savings attained by the proposed approach, particularly for large values of the odds ratio parameter and for small proportions of dichotomized successes or failures. In a Monte Carlo simulation the variances and absolute biases of the two odds ratio estimators and the length of their respective confidence intervals again demonstrate the improvement attained by the proposed approach. In addition, coverage probabilities of the confidence intervals of the proposed approach converge quickly to the nominal levels. The cost savings due to the reduction in required sample size when using this method make it a very attractive study design and analysis tool for medical researchers. Copyright © 2004 John Wiley & Sons, Ltd.
Displaying dependence graphs: a hierarchical approach
Authors: Balmas F.
Published: May 2004

We present a method to extract and handle data and control dependences of programs, which we represent as simplified system dependence graphs. Ordinary dependence graphs contain too many nodes and edges for them to be easily comprehended, even for medium sized programs. That is why we propose decomposing programs into a hierarchy of groups for which the corresponding dependence graphs are likely to be of manageable size. In order to realize this, we first implement a tool that builds this hierarchy and stores it in a database. Then a graphical interface provides means to browse the hierarchy, to visualize the dependences of each group, to possibly refine the proposed hierarchy and to annotate nodes or groups.

This paper introduces our approach for dependence graph handling, it describes our tool for graph exploration and discusses the results we obtained with a set of real‐world programs. Copyright © 2004 John Wiley & Sons, Ltd.
The implementation of generic smart pointers for advanced defensive programming
Authors: Savidis Anthony
Published: May 2004

Smart pointers denote a well‐known technique for collective resource ownership, e.g. sharing dynamic object instances, while usually supporting automatic garbage collection based on reference counting. The original method has been retargeted to serve as a generic defensive programming method for ‘exhaustive tracking’ of erroneous pointer use in C++. Automatic bug tracking is supported in a unified manner both for pointers to heap memory, i.e. free storage, as well as for pointers to stack or global memory, i.e. auto or static storage. Overall, the presented technique (a) offers a simple contract for memory allocation and use; (b) supports type and indirection depth genericity; (c) implements most operators supported for built‐in pointers with embedded bug defense; (d) offers an alternative way of employing a garbage collection facility for memory leak detection; and (e) provides an appropriate collection of utility macros, through which defensive pointers should be used, with an alternative version re‐targeted to normal native pointers. Copyright © 2004 John Wiley & Sons, Ltd.
Differential properties of GABAergic synaptic connections in rat hippocampal cell cultures
Authors: Ivanova Svetlana Y. , Lushnikova Irina V. , Pivneva Tatyana A. , Belan Pavel V. , Storozhuk Maksim V. , Kostyuk Platon G.
Published: May 2004

Based on the effect of prolonged tetanic stimulation (30 Hz, 4 sec), we divided GABAergic synaptic connections in hippocampal cell cultures into two groups: connections facilitated (∼45%) and connections depressed (∼55%) by the tetanic stimulation. In order to reveal possible reasons for the differential effect of the tetanization, we compared several properties of the connections belonging to both groups. We found that, on average, evoked IPSCs in the connections facilitated by the tetanization have a smaller amplitude and larger coefficient of variation (CV) of IPSC amplitude compared to connections depressed by the tetanization. We also estimated quantal parameters for both groups of connections assuming that transmitter release is reasonably described by a binomial distribution. We found that a background release probability (P) is substantially lower in the connections facilitated by the tetanization (P ∼0.5) than in the connections depressed by the tetanization (P ∼0.9) and suggest that this difference may underlie the differential effect of the tetanization. We also found that the tetanization induces the opposite effect on connections made by distinct presynaptic neurons with the same postsynaptic cell (convergent connections) in a fraction of postsynaptic neurons studied (3 out of 9). These results support the idea that properties of the presynaptic neuron are of primary importance for the observed differential effect of the tetanization, but they do not exclude a role of the postsynaptic neuron in this effect. Synapse 53:122–130, 2004. © 2004 Wiley‐Liss, Inc.
Investigation of occiput posterior delivery by intrapartum sonography
Authors: Akmal S. , Tsoi E. , Howard R. , Osei E. , Nicolaides K. H.
Published: May 2004

Objective

To investigate if occiput posterior delivery is the consequence of persistence of an initial occiput posterior position or malrotation from an initial occiput anterior or transverse position.

Methods

This was a cross‐sectional study involving transabdominal sonography to determine fetal occipital position in 918 singleton pregnancies with cephalic presentation in active labor at 37–42 weeks of gestation. The relationship between occipital position in labor and at delivery was examined.

Results

The occiput was posterior in 33.0% (149/452), 33.9% (101/298) and 19.0% (32/168) of fetuses at the respective cervical dilatations of 3–5, 6–9 and 10 cm and this persisted at delivery in 21.5% (32/149), 31.7% (32/101) and 43.8% (14/32) of cases. In 70% (32/46), 91% (32/35) and 100% (14/14) of occiput posterior deliveries there was persistence from this position at 3–5, 6–9 and 10 cm of cervical dilation.

Conclusions

The majority of occiput posterior positions during labor rotate to the anterior position even at 10 cm of cervical dilatation. However, the vast majority of occiput posterior positions at delivery are a consequence of persistence of this position during labor rather than malrotation from an initial occiput anterior or transverse position. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Galactic cosmic ray modulation: Effects of the solar wind termination shock and the heliosheath
Authors: Caballero‐Lopez R. A. , Moraal H. , McDonald F. B.
Published: May 2004

This paper studies the radial intensity profiles of galactic cosmic ray protons (H) and α particles (He) during the solar minimum periods of 1987 (the so‐called negative drift state) and 1977/1997 (both positive drift states). These intensities, as measured with the Pioneers 10/11, Voyagers 1/2, and IMP spacecraft, are examined with numerical solutions of the cosmic ray transport equation. Previous studies have shown that the galactic cosmic ray intensities and radial gradients observed by the Voyagers during 1997 in the outer heliosphere were so low that they cannot be readily explained by a standard no‐shock modulation model. Here we investigate whether acceleration at the solar wind termination shock and the transport of these particles through an extended heliosheath beyond this shock provide sufficient additional modulation to explain these low intensities. In this approach we take into account several different heliomagnetic field configurations. It is found that the acceleration at the termination shock and modulation in the heliosheath do not alleviate the problem but that a nonspherical shock and heliopause produce modulation features that may possibly explain the observations. These shock and heliosheath effects are discussed in detail.
Millennial‐scale fluctuations in subtropical northwestern Atlantic surface ocean hydrography during the mid‐Pleistocene
Authors: Billups K. , Chaisson W. , Worsnopp M. , Thunell R.
Published: May 2004

We use planktonic foraminiferal (Globigerinoides sacculifer and Neogloboquadrina dutertrei) δ18O records from subtropical North Atlantic Site 1056 to reconstruct millennial‐scale changes in sea surface hydrography during marine isotope stages (MIS) 10 through 12 (∼340–440 ka). The difference in the δ18O records provides a measure of the thermal gradient from the mixed layer to the seasonal thermocline (ΔTml‐tc), which we use to constrain upper ocean stratification and infer northward ocean heat transport. Late Holocene G. sacculifer and N. dutertrei δ18O values place controls on how the foraminifera record recent ocean conditions at Site 1056. In the down core record we find extreme excursions toward G. sacculifer δ18O maxima and ΔTml‐tc minima throughout the entire time interval. These cold events have a similar amplitude throughout but are more frequent during the glacial than the interglacial intervals. During interglacial MIS 11 the excursions provide evidence for repeated cooling of the sea surface contributing to existing evidence for relative climate instability during interglacial intervals. During MIS 10, millennial‐scale variability in the subtropical record is very similar to that observed in the subpolar North Atlantic at Site 980, perhaps related to a common forcing such as a large Northern Hemisphere ice sheet. Within the limitation of the age models the cold events of MIS 11 are almost synchronous with benthic foraminiferal δ13C minima at subtropical North Atlantic Site 1063, which suggests a general surface to deep ocean link via thermohaline circulation during this interval of time.
Multi-scale continuum mechanics: From global bifurcations to noise induced high-dimensional chaos
Authors: Schwartz Ira B. , Morgan David S. , Billings Lora , Lai Ying-Cheng
Published: May 2004

Many mechanical systems consist of continuum mechanical structures, having either linear or nonlinear elasticity or geometry, coupled to nonlinear oscillators. In this paper, we consider the class of linear continua coupled to mechanical pendula. In such mechanical systems, there often exist several natural time scales determined by the physics of the problem. Using a time scale splitting, we analyze a prototypical structural–mechanical system consisting of a planar nonlinear pendulum coupled to a flexible rod made of linear viscoelastic material. In this system both low-dimensional and high-dimensional chaos is observed. The low-dimensional chaos appears in the limit of small coupling between the continua and oscillator, where the natural frequency of the primary mode of the rod is much greater than the natural frequency of the pendulum. In this case, the motion resides on a slow manifold. As the coupling is increased, global motion moves off of the slow manifold and high-dimensional chaos is observed. We present a numerical bifurcation analysis of the resulting system illustrating the mechanism for the onset of high-dimensional chaos. Constrained invariant sets are computed to reveal a process from low-dimensional to high-dimensional transitions. Applications will be to both deterministic and stochastic bifurcations. Practical implications of the bifurcation from low-dimensional to high-dimensional chaos for detection of damage as well as global effects of noise will also be discussed.
Oscillations and change of sign in indirect exchange coupling of Fe/Au/Tb trilayer structures
Authors: Shypil E. , Pogorily A. , Podyalovsky D.
Published: May 2004

The indirect exchange coupling between Fe and Tb layers through an Au layer exhibits oscillatory behavior with respect to the thickness of the nonmagnetic metal. Different experimental tools such as the polar magnetooptical Kerr effect, ferromagnetic resonance, and magnetotransport were used to investigate Fe/Au/Tb trilayers with Au thickness varying from 0 to 3.5 nm, prepared in an MBE system. From the experimental data we reconstruct the dynamics of the Fe and Tb magnetic moments with increasing thickness of the Au interlayer and show for the first time that there is a change of sign in the interaction between Fe and Tb, which is observed experimentally.
Calculation of free energy through successive umbrella sampling
Authors: Virnau Peter , Müller Marcus
Published: May 2004

We consider an implementation of umbrella sampling in which the pertinent range of states is subdivided into small windows that are sampled consecutively and linked together. This allows us to simulate without a weight function or to extrapolate the results to the neighboring window in order to estimate a weight function. Additionally, we present a detailed error analysis in which we demonstrate that the error in umbrella sampling is controlled and, in the absence of sampling difficulties, independent of the window sizes. In this case, the efficiency of our implementation is comparable to a multicanonical simulation with a very good weight function, which in our scheme does not need to be known ahead of time. The analysis also allows us to detect sampling difficulties such as correlations between adjacent windows and provides a test of equilibration. We exemplify the scheme by simulating the liquid–vapor coexistence in a Lennard-Jones system.
High-efficiency 269 nm emission deep ultraviolet light-emitting diodes
Authors: Adivarahan V. , Wu S. , Zhang J. P. , Chitnis A. , Shatalov M. , Mandavilli V. , Gaska R. , Khan M. Asif
Published: May 2004

We report on 269 nm emission deep ultraviolet light-emitting diodes (LEDs) over sapphire. The material quality, device design, and contact processing sequence yielded devices with external quantum efficiencies as high as 0.4% for a pumped pulse current of 200 mA and 0.32% for a dc pump current of 10 mA. For a module of two LEDs connected in series, a record continuous-wave power of 0.85 mW (at 40 mA) and a wall plug efficiency of 0.16% (at 10 mA dc) were measured.
Optical and electrical properties of (1-101)GaN grown on a 7° off-axis (001)Si substrate
Authors: Hikosaka T. , Narita T. , Honda Y. , Yamaguchi M. , Sawaki N.
Published: May 2004

Uniform growth of (1-101)GaN was performed on coalesced stripes of GaN which had been prepared by selective metalorganic vapor phase epitaxy on a 7° off-axis (001)Si substrate via an AlN intermediate layer. The cathodoluminescence spectra at 4 K exhibited a donor bound excitonic emission at 358 nm followed by defect-related emission peaks at 363, 371, and 376 nm. The 363 and 376 emission bands are observed upon the coalescence region. The Hall measurements exhibited p-type conduction at 80–300 K (the hole carrier density 6.3×1012 cm−2 and hole mobility 278 cm2/V s at 100 K). The activation energy of the acceptor was estimated to be 60 meV. The possible origin of the p-type conduction is discussed in relation to the unintentionally doped carbon.
Energy distribution of the (100)Si/HfO2 interface states
Authors: Fedorenko Y. G. , Truong L. , Afanas’ev V. V. , Stesmans A.
Published: May 2004

The energy distributions of interface states were determined in (100)Si/HfO2 using capacitance–voltage measurements on structures with the periphery of the metal electrode switched to inversion by controlled application of corona discharge. Together with independently applied ac conductance spectroscopy they reveal a strong impact of the HfO2 deposition technique on the interface trap density. This includes the enhancement of the Si-dangling bond defect (Pb0 centers) density and a contribution of insulator-related traps in samples deposited using a nitrogen-containing precursor.
Transport properties of [2,2]-paracyclophane thin films
Authors: Hu Wenping , Gompf Bruno , Pflaum Jens , Schweitzer Dieter , Dressel Martin
Published: May 2004

The transport properties of [2,2]-paracyclophane thin films prepared by molecular beam epitaxy were studied by space-charge-limited current measurements. This organic semiconductor, which has a three-dimensional π-system comparable to that of C60, is an interesting material for molecular electronic applications due to its remarkably high mobility and its insensitivity against photo-oxidation. The current–voltage characteristics were recorded using a coplanar electrode geometry which has the advantage, that after deposition no further processing of the organic semiconducting layer is necessary. In polycrystalline films hole mobilities up to 10−2 cm2 V−1 s−1 were observed at room temperature.
Silicon nanopillars for mechanical single-electron transport
Authors: Scheible Dominik V. , Blick Robert H.
Published: May 2004

Nanomechanical systems have been shown to accurately regulate the flow of electric current. We present the concept and demonstrate experimental operation of a vertical electromechanical single-electron transistor. The device is fabricated from silicon forming a nanopillar situated between source and drain contacts. The advantage of this concept is its straightforward manufacturing, which only includes two processing steps: Electron-beam lithography and reactive ion etching. The device operates at room temperature and at frequencies in the range of 350–400 MHz. A theoretical model of the operation of this device is given, explaining qualitatively the obtained experimental data.
Stacking of InAs/InP(001) quantum wires studied by in situ stress measurements: Role of inhomogeneous stress fields
Authors: Fuster David , Ujué González Marı́a , González Luisa , González Yolanda , Ben Teresa , Ponce Arturo , Molina Sergio I.
Published: May 2004

Size and spatial distribution homogeneity of nanostructures is greatly improved by making stacks of nanostructures separated by thin spacers. In this work, we present in situ and in real time stress measurements and reflection high-energy electron diffraction observations and ex situ transmission electron microscopy (TEM) characterization of stacked layers of InAs quantum wires (QWRs) separated by InP spacer layers, d(InP), of thickness between 3 and 20 nm. For d(InP)<20 nm, the amount of InAs involved in the created QWR from the second stack layer on, exceeds that provided by the In cell. Our results suggest that in those cases InAs three dimensional islands formation starts at the P/As switching and lasts during further InAs deposition. We propose an explanation for this process that is strongly supported on TEM observations. The results obtained in this work imply that concepts like the existence of a critical thickness for two- to three-dimensional growth mode transition should be revised in correlated QWR stacks of layers.
Stress profile and thermal expansion of layered materials determined from surface stresses
Authors: Malzbender Jürgen
Published: May 2004

A simple method of inferring the stress profile and the effective difference in thermal expansion or strain in an unconstrained elastic multilayer system from a measurement of a limited number of surface stresses as obtained for example using x-ray diffraction or Raman spectroscopy is outlined. Explicit relationships are given for bilayered systems. The analysis procedure is exemplified for literature data of electronics materials, solid oxide fuel cells and thermal barrier systems. Following the outlined procedure, a determination of the stress profile and difference in thermal expansion for composites of alternating layers is also possible.
Low-resistance and transparent ohmic contacts to p-type GaN using Zn–Ni solid solution/Au scheme
Authors: Song June-O , Leem Dong-Seok , Seong Tae-Yeon
Published: May 2004

High-quality Zn–Ni solid solution(8 nm)/Au(8 nm) ohmic contacts on p-GaN (5×1017 cm−3) have been investigated by means of current–voltage (I–V) measurements and x-ray photoemission spectroscopy. The as-deposited contact shows nonlinear I–V characteristics. However, oxidizing the contacts at 530 °C for 1 min in air ambient gives rise to considerable improvement in their I–V behaviors, yielding a specific contact resistance of 5.2×10−5 Ω cm2. The light transmittance of the annealed Zn–Ni solid solution/Au contacts is measured to be better than 74% at a wavelength of 470 nm. Green light-emitting diodes (LEDs) fabricated with the annealed Zn–Ni solid solution/Au contacts give a forward-bias voltage of 3.39 V at an injection current of 20 mA, which is better than that of the LEDs with the oxidized Ni/Au contacts.