bluuebunny/crossref_metadata_2025 huggingface dataset:
A multiagent approach to power system normal operation
Authors: Nagata Takeshi , Nakamura Hiroyuki , Nakamura Yoriko , Utatani Masahiro , Sasaki Hiroshi
Published: January 2004

Recently, the electric utility industry worldwide has been facing pressure to be deregulated or restructured in order to increase its efficiency, to reduce operational cost, or to give consumers more alternatives. For this aspect, a great deal more research is needed to achieve a better, intelligent knowledge process. The present centralized system for power system control, operation, and planning must be remodeled to cope with these situations. With the promotion for the deregulation of the electric power system, the definition of the objective function for the optimization problem such as outage work operation for electric power systems is becoming critical. Currently, agents are an intense focus in many subfields of computer science and artificial intelligence. Agents are being used in an increasingly wide variety of applications.

In this paper, we developed a power system normal operation application by multiagent architecture. Our multiagent system consists of several facilitator agents, equipment agents, and switch‐box agents. Facilitator agent acts as a manager for negotiation process between agents. Equipment agent corresponds to the element of the electric power system, such as bus, transformer, and transmission line, while switch‐box agent is the pseudo object which consists of neighboring current breakers and disconnecting switches. The proposed system realizes the appropriate switching operations by interacting with corresponding agents. The proposed approach is applied to a simple network, and the results show that the proposed multiagent system is an efficient decentralized approach for solving power system normal operations. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 26–33, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10227
A design of multivariable, self‐tuning PID controllers with an internal model structure
Authors: Ohnishi Yoshihiro , Yamamoto Toru , Omatu Sigeru
Published: January 2004

Self‐tuning control schemes (STC) are useful for systems with unknown or slowly time‐varying parameters. Some single‐input/single‐output PID control schemes based on STCs have been proposed for such systems. However, there are a lot of multivariable systems in real process industries. And these systems often have relatively large time delays. In this paper, a design scheme of self‐tuning PID control system is proposed for multivariable systems with unknown parameters and time delays. The controlled object is equipped with an internal model in order to compensate the time delay and also unstable zeros. Subsequently, a multivariable PID controller is designed for the augmented or compensated system. The PID parameters are calculated recursively based on the relationship between the minimum variance control law and the PID control law. A simulation example is presented to demonstrate the effectiveness of the proposed scheme. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 58–64, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10241
Guaranteed cost control for large‐scale systems under control gain perturbations
Authors: Mukaidani Hiroaki , Tanaka Yoshiyuki , Mizukami Koichi
Published: January 2004

The guaranteed cost control problem of the decentralized robust control for large‐scale systems with the norm‐bounded time‐varying parameter uncertainties and a given quadratic cost function is considered. Sufficient conditions for the existence of guaranteed cost controllers are given in terms of linear matrix inequality (LMI). It is shown that decentralized local state feedback controllers can be obtained by solving the LMI. The problem of guaranteed cost control for large‐scale systems under the gain perturbations is also considered. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 43–57, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10265
Current tracking control of voltage source PWM inverters using adaptive digital signal processing
Authors: Fukuda Shoji , Furukawa Yuya
Published: January 2004

An active filter (AF) is required to have a high control capability for tracking a time‐varying current reference. However, a steady‐state current error always exists if a conventional proportional and integral (PI) regulator is used because the current reference varies in time. This paper proposes the application of adaptive digital signal processing (ADSP) to the current control of voltage source PWM inverters. ADSP does not require any additional hardware. It can automatically minimize the mean‐square error. Since the available computer processing time is limited, ADSP cannot eliminate higher‐order harmonics but can eliminate lower‐order harmonics such as 5th to 17th. Experimental results demonstrate that ADSP is useful for improving the reference tracking performance of voltage source inverters. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 76–83, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10266
Employment of the second‐moment turbulence closure on arbitrary unstructured grids
Authors: Basara B.
Published: January 2004

The paper presents a finite‐volume calculation procedure using a second‐moment turbulence closure. The proposed method is based on a collocated variable arrangement and especially adopted for unstructured grids consisting of ‘polyhedral’ calculation volumes. An inclusion of 23k in the pressure is analysed and the impact of such an approach on the employment of the constant static pressure boundary is addressed. It is shown that this approach allows a removal of a standard but cumbersome velocity–pressure –Reynolds stress coupling procedure known as an extension of Rhie‐Chow method (AIAA J. 1983; 21: 1525–1532) for the Reynolds stresses. A novel wall treatment for the Reynolds‐stress equations and ‘polyhedral’ calculation volumes is presented. Important issues related to treatments of diffusion terms in momentum and Reynolds‐stress equations are also discussed and a new approach is proposed. Special interpolation practices implemented in a deferred‐correction fashion and related to all equations, are explained in detail. Computational results are compared with available experimental data for four very different applications: the flow in a two‐dimensional 180o turned U‐bend, the vortex shedding flow around a square cylinder, the flow around Ahmed Body and in‐cylinder engine flow. Additionally, the performance of the methodology is assessed by applying it to different computational grids. For all test cases, predictions with the second‐moment closure are compared to those of the k–εmodel. The second‐moment turbulence closure always achieves closer agreement with the measurements. A moderate increase in computing time is required for the calculations with the second‐moment closure. Copyright © 2004 John Wiley & Sons, Ltd.
An upwind compact mpact approach with group velocity control for compressible flow fields
Authors: Zhu Qingyong , Li Yi
Published: January 2004

In this paper we construct an upwind compact finite difference scheme with group velocity control for better simulation of compressible flow fields. Compared with traditional difference schemes, compact schemes have higher accuracy for the same stencil width. By means of the characteristic analysis of the operators, the group velocity of wave packets will be controlled to suppress the non‐physical oscillations in numerical solutions. In numerical simulation of the 3D compressible flow fields the third‐order accurate upwind compact operator is used to approximate the derivatives in the convection terms of the compressible N–S equations, the traditional finite difference scheme is used to approximate the viscous terms. Numerical solutions indicate that the method is satisfactory. Copyright © 2004 John Wiley & Sons, Ltd.
A numerical and experimental investigation of the interactions between a non‐uniform planar array of incompressible free jets
Authors: Manohar C. H. Isaac , Sundararajan T. , Ramjee V. , Kumar S. Sasi
Published: January 2004

The interaction between multiple incompressible air jets has been studied numerically and experimentally. The numerical predictions have been first validated using experimental data for a single jet configuration. The spreading features of five unequal jets in the configuration of one larger central jet surrounded by four smaller equi‐distant jets, have been studied, for different lateral spacing ratios of 1.5, 2.0 and 2.5 and a central jet Reynolds number of 1.24×105 (corresponding to a Mach number of 0.16). Flow of five equal jets has also been simulated, for the sake of comparison. The jet interactions commence at an axial distance of about 3–4 diameters and complete by an axial distance of about 10 diameters for the lowest spacing ratio of 1.5. For larger spacing ratios, the length required for the start and completion of jet interaction increase. Peripheral jets bend more towards the central jet and merge at a smaller distance, when their sizes are smaller than that of the central jet. The entrainment ratio for multiple jets is higher than that for a single jet. Excellent agreement is observed between the experimental data and theoretical predictions for both mean flow field and turbulent quantities, at regions away from the jet inlet. The potential core length and initial jet development, however, are not predicted very accurately due to differences in the assumed and actual velocity profiles at the jet inlet. Copyright © 2004 John Wiley & Sons, Ltd.
Forecasting football results and the efficiency of fixed‐odds betting
Authors: Goddard John , Asimakopoulos Ioannis
Published: January 2004

An ordered probit regression model estimated using 10 years' data is used to forecast English league football match results. As well as past match results data, the significance of the match for end‐of‐season league outcomes, the involvement of the teams in cup competition and the geographical distance between the two teams' home towns all contribute to the forecasting model's performance. The model is used to test the weak‐form efficiency of prices in the fixed‐odds betting market. A strategy of selecting end‐of‐season bets with a favourable expected return according to the model appears capable of generating a positive return. Copyright © 2004 John Wiley & Sons, Ltd.
Medium‐term forecasts of potential GDP and inflation using age structure information
Authors: Lindh Thomas
Published: January 2004

Economic behaviour as well as economic resources of individuals vary with age. Swedish time series show that the age structure contains information correlated to medium‐term trends in growth and inflation. GDP gaps estimated by age structure regressions are closely related to conventional measures. Monetary policy is believed to affect inflation with a lag of 1 or 2 years. Projections of the population's age structure are comparatively reliable several years ahead and provide additional information to improve on 3–5 years‐ahead forecasts of potential GDP and inflation. Thus there is a potential scope for using age structure based forecasts as an aid to monetary policy formation. Copyright © 2004 John Wiley & Sons, Ltd.
Efficient Simulation of P Values for Linkage Analysis
Authors: Song Kyunghee K. , Weeks Daniel E. , Sobel Eric , Feingold Eleanor
Published: January 2004

In many genetic linkage analyses, the P value is obtained through simulation since the underlying distribution of the test statistic is complex and unknown. However, this can be very computationally intensive. A “bootstrap/replicate pool” approach has been suggested that generates P values more efficiently in terms of computation by resampling sums from a small set of simulated replicates for each pedigree. The replicate pool idea has been successfully applied, but, to our knowledge, has never been theoretically studied. An entirely different method for increasing the computational efficiency of P value simulation is Besag and Clifford's sequential sampling method. We propose an algorithm which combines Besag and Clifford's method with the replicate pool method to efficiently estimate P values for linkage studies. We derive variance expressions for the P value estimates from the replicate pool method and from our proposed hybrid method, and use these to show that the hybrid estimator has a substantial advantage over the other methods in most situations. Genet Epidemiol 26: 88–96, 2004. © 2004 Wiley‐Liss, Inc.
What SNP genotyping errors are most costly for genetic association studies?
Authors: Kang Sun Jung , Gordon Derek , Finch Stephen J.
Published: January 2004

Which genotype misclassification errors are most costly, in terms of increased sample size necessary (SSN) to maintain constant asymptotic power and significance level, when performing case/control studies of genetic association? We answer this question for single‐nucleotide polymorphisms (SNPs), using the 2×3χ2test of independence. Our strategy is to expand the noncentrality parameter of the asymptotic distribution of theχ2test under a specified alternative hypothesis to approximate SSN, using a linear Taylor series in the error parameters. We consider two scenarios: the first assumes Hardy‐Weinberg equilibrium (HWE) for the true genotypes in both cases and controls, and the second assumes HWE only in controls. The Taylor series approximation has a relative error of less than 1% when each error rate is less than 2%. The most costly error is recording the more common homozygote as the less common homozygote, with indefinitely increasing cost coefficient as minor SNP allele frequencies approach 0 in both scenarios. The cost of misclassifying the more common homozygote to the heterozygote also becomes indefinitely large as the minor SNP allele frequency goes to 0 under both scenarios. For the violation of HWE modeled here, the cost of misclassifying a heterozygote to the less common homozygote becomes large, although bounded. Therefore, the use of SNPs with a small minor allele frequency requires careful attention to the frequency of genotyping errors to ensure that power specifications are met. Furthermore, the design of automated genotyping should minimize those errors whose cost coefficients can become indefinitely large.Genet Epidemiol26:132–141, 2004. © 2004 Wiley‐Liss, Inc.
Monetary policy rules in practice: evidence from Turkey
Authors: Berument Hakan , Taşçi Hakan
Published: January 2004

This paper estimates a forward‐looking monetary policy reaction function of the Central Bank of the Republic of Turkey by considering the period from 1990:01 to 2000:10. When the spread between the interbank rate and depreciation rate of the local currency is taken as a policy tool, the empirical evidence suggests that the Turkish Central Bank responds to its foreign exchange reserves, output and M2 growth not the forward, current or lagged inflation. Copyright © 2003 John Wiley & Sons, Ltd.
Protective effect of α‐lipoic acid against chloroquine‐induced hepatotoxicity in rats
Authors: Pari L. , Murugavel P.
Published: January 2004

Oral administration of a‐lipoic acid, a metavitamin, was investigated for its possible hepatoprotective effect in Wistar rats against chloroquine‐induced toxicity. Rats were treated orally with α‐lipoic acid (10, 30 and 100 mg kg−1 day−1) for 7 days before a single oral administration of chloroquine (970 mg kg−1 day−1) and α‐lipoic acid treatment was continued for three more days. The increased level of serum enzymes (aspartate transaminase, alanine transaminase and alkaline phosphatase), bilirubin, lipids and plasma thiobarbituric acid‐reactive substances (TBARS) and hydroperoxides observed in rats treated with chloroquine were very much reduced in rats treated with α‐lipoic acid plus chloroquine. A signiﬁcant decrease in plasma antioxidants such as reduced glutathione (GSH), vitamin C and vitamin E were observed in chloroquine‐treated rats when compared with control rats. Administration of α‐lipoic acid signiﬁcantly improved the levels of plasma antioxidants GSH, vitamin C and vitamin E in chloroquine‐treated rats. In the case of 100 mg kg−1 day−1 the effect was highly signiﬁcant compared with the other doses (10 and 30 mg kg−1 day−1). The results of the study revealed that α‐lipoic acid could offer protection against chloroquine‐induced hepatotoxicity. α‐Lipoic acid had a better protective effect when compared with silymarin, a reference drug. Copyright © 2004 John Wiley & Sons, Ltd.
Protective effects of caffeic acid phenethyl ester on doxorubicin‐induced cardiotoxicity in rats
Authors: Fadillioglu Ersin , Oztas Emin , Erdogan Hasan , Yagmurca Murat , Sogut Sadik , Ucar Muharrem , Irmak M. Kemal
Published: January 2004

The prevention of doxorubicin (DXR)‐induced cardiotoxicity may be helpful to improve future DXR therapy. The aim of this study was to investigate the cardio‐protective effects of caffeic acid phenethyl ester (CAPE), an antioxidant agent, on DXR‐induced cardiotoxicity. Rats were divided into three groups and treated with saline, DXR and DXR + CAPE. Rats were treated with CAPE (10 µmol kg−1 day−1 i.p.) or saline starting 2 days before a single dose of DXR (20 mg kg−1 i.p.). Ten days later, haemodynamic measurements were performed and the hearts were excised for biochemical analyses and microscopic examination. The heart rate and mean blood pressure were higher and the pulse pressure was lower in the DXR group than in the other two groups. The administration of DXR alone resulted in higher myeloperoxidase activity, lipid peroxidation and protein carbonyl content than in the other groups. The activities of superoxide dismutase and catalase were higher in DXR and DXR + CAPE groups than in the saline group. Rats in the DXR + CAPE group had increased catalase activity in comparison with the DXR group and high glutathione peroxidase activity in comparison with the other two groups. There was severe disruption of mitochondrial ﬁne structure in the electron microscopy of the DXR group. In contrast, myocardial microscopy appeared nearly normal in the DXR + CAPE group (as deﬁned at the electron microscopic level). In light of these in vivo haemodynamic, enzymatic and morphological results, we conclude that CAPE pretreatment signiﬁcantly attenuated DXR‐induced cardiac injury, possibly with its antioxidant effects. Copyright © 2004 John Wiley & Sons, Ltd.
Adrenal toxicity in dogs and cats as a contributing cause of hormonal and immune destabilization
Authors: Plechner Alfred J.
Published: January 2004

The adrenal cortex is regarded as the organ most vulnerable to toxicity within the endocrine system. The production of cortisol, among the many steroidal hormones produced by the cortex, may suffer as a result. In a veterinary clinical practice, household dogs and cats with a wide variety of diseases ranging from allergies to cancer commonly have a cortisol deﬁciency or defect that triggers endocrine imbalances and immune system destabilization. The causes of deﬁcient cortisol are linked primarily to genetics but also to acquired adrenal damage likely stemming from environmental toxins. An innovative blood test to determine relevant endocrine–immune imbalances in pets and a treatment method based on low‐dosage steroidal medication, as a form of cortisol replacement therapy, are described. Despite a prevailing reluctance to use steroidal medications long term because of the fear of side effects, extended and even life‐time usage of these medications at low, physiologic dosages has been applied successfully for decades and appears to be gaining wider acceptance. The validity of a combined testing and treatment method for humans based on the veterinary model deserves investigation as a tool with which to identify and correct toxic damage to adrenal function. Copyright © 2004 John Wiley & Sons, Ltd.
Mouse strain differences in eosinophilic airway inﬂammation caused by intratracheal instillation of mite allergen and diesel exhaust particles
Authors: Ichinose Takamichi , Takano Hirohisa , Sadakane Kaori , Yanagisawa Rie , Yoshikawa Toshikazu , Sagai Masaru , Shibamoto Takayuki
Published: January 2004

Response differences by different strains of mice towards house dust mites (Dermatophagoides farinae) or diesel exhaust particles (DEP) were investigated. Mouse strains BALB/c, ICR and C3H/He received 1 µg of D. farinae or 1 µg of D. farinae + 50 µg of DEP intratracheally four times at 2‐week intervals. Dermatophagoides farinae treatment caused the recruitment of eosinophils and lymphocytes. The order of magnitude of the eosinophilic airway inﬂammation was BALB/c < ICR < C3H/He mice. The protein levels of eotaxin and IL‐5 in lung tissues correlated with the manifestations of eosinophilic airway inﬂammation by D. farinae administration. Diesel exhaust particles aggravated the manifestation of the eosinophilic inﬂammation through goblet cell proliferation in the airway and enhanced the local expression of eotaxin and IL‐5 in all three strains of mice. The levels of eotaxin and IL‐5 in lung tissues corresponded to the pathological changes caused by D. farinae + DEP. The increasing order of production levels of antigen‐speciﬁc IgG1 by D. farinae or D. farinae + DEP was BALB/c < ICR < C3H/He mice. The signiﬁcant adjuvant effect of DEP on IgG1 production was observed in the C3H/He mice (P < 0.05). These results suggest that the murine strain differences in the production of eosinophilic airway inﬂammation by D. farinae + DEP are related to differences in local expression of IL‐5 and eotaxin. The enhancing effects of DEP may be mediated by a cytokine increase in the local expression. Antigen‐speciﬁc IgG1 may be an important immunoglobulin in the pathogenesis of allergic asthma enhanced by DEP. Copyright © 2004 John Wiley & Sons, Ltd.
Signiﬁcance of the detection of esters of p‐hydroxybenzoic acid (parabens) in human breast tumours
Authors: Harvey Philip W. , Everett David J.
Published: January 2004

This issue of Journal of Applied Toxicology publishes the paper Concentrations of Parabens in Human Breast Tumours by Darbre et al. (2004), which reports that esters of p‐hydroxybenzoic acid (parabens) can be detected in samples of tissue from human breast tumours. Breast tumour samples were supplied from 20 patients, in collaboration with the Edinburgh Breast Unit Research Group, and analysed by high‐pressure liquid chromatography and tandem mass spectrometry. The parabens are used as antimicrobial preservatives in underarm deodorants and antiperspirants and in a wide range of other consumer products. The parabens also have inherent oestrogenic and other hormone related activity (increased progesterone receptor gene expression). As oestrogen is a major aetiological factor in the growth and development of the majority of human breast cancers, it has been previously suggested by Darbre that parabens and other chemicals in underarm cosmetics may contribute to the rising incidence of breast cancer. The signiﬁcance of the ﬁnding of parabens in tumour samples is discussed here in terms of 1) Darbre et al's study design, 2) what can be inferred from this type of data (and what can not, such as the cause of these tumours), 3) the toxicology of these compounds and 4) the limitations of the existing toxicology database and the need to consider data that is appropriate to human exposures. Copyright © 2004 John Wiley & Sons, Ltd.
On the 3BD‐closed set B3({4,5,6})
Authors: Ji L.
Published: January 2004

Let B3(K) = {v:∃ an S(3,K,v)}. For K = {4} or {4,6}, B3(K) has been determined by Hanani, and for K = {4, 5} by a previous paper of the author. In this paper, we investigate the case of K = {4,5,6}. It is easy to see that if v ∈ B3 ({4, 5, 6}), then v ≡ 0, 1, 2 (mod 4). It is known that B3{4, 6}) = {v > 0: v ≡ 0 (mod 2)} ⊂ B3({4,5,6}) by Hanani and that B3({4, 5}) = {v > 0: v ≡ 1, 2, 4, 5, 8, 10 (mod 12) and v ≠ 13} ⊂ B3({4, 5, 6}). We shall focus on the case of v ≡ 9 (mod 12). It is proved that B3({4,5,6}) = {v > 0: v ≡ 0, 1, 2 (mod 4) and v ≠ 9, 13}. © 2003 Wiley Periodicals, Inc.
Concerning seven and eight mutually orthogonal Latin squares
Authors: R. Abel R. Julian , Colbourn Charles J. , Wojtas Mieczyslaw
Published: January 2004

In this paper, three new direct Mutually Orthogonal Latin Squares (MOLS) constructions are presented for 7 MOLS(24), 7 MOLS(75) and 8 MOLS(36); then using recursive methods, several new constructions for 7 and 8 MOLS are obtained. These reduce the largest value for which 7 MOLS are unknown from 780 to 570, and the largest odd value for which 8 MOLS are unknown from 1935 to 419. © 2003 Wiley Periodicals, Inc.
Magnetic resonance portography using contrast‐enhanced fat‐saturated three‐dimensional steady‐state free precession imaging
Authors: Amano Yasuo , Takahama Katsuya , Nozaki Atsushi , Amano Maki , Kumazaki Tatsuo
Published: January 2004

Purpose

To assess the feasibility of contrast‐enhanced fat‐saturated three‐dimensional steady‐state free precession (FIESTA) imaging for contrast‐enhanced magnetic resonance (MR) portography.

Materials and Methods

Contrast‐enhanced fat‐saturated three‐dimensional fast spoiled gradient‐echo (SPGR) and FIESTA were performed as MR portography. In 10 cases, fat‐saturated three‐dimensional FIESTA was first performed and followed by fast SPGR, and the order of post‐contrast imaging was reversed in the other 10 cases. Signal‐to‐noise ratios (SNRs) and contrast‐to‐noise ratios (CNRs) were estimated for portal and visceral veins on the source images. The visualization of portal vein was scored on three‐dimensional MR portography. Portal venous system disorders were assessed using three‐dimensional MR portography.

Results

The SNRs, CNRs, and visual assessment of portal and visceral veins were significantly higher in contrast‐enhanced fat‐saturated three‐dimensional FIESTA than contrast‐enhanced fat‐saturated three‐dimensional fast SPGR (P < 0.05). The contrast‐enhanced fat‐saturated three‐dimensional FIESTA provided high venous signals even at 8 minutes after gadolinium injection. The abnormalities of portal venous system were well visualized with MR portography using contrast‐enhanced fat‐saturated three‐dimensional FIESTA.

Conclusion

Contrast‐enhanced fat‐saturated three‐dimensional FIESTA was valuable for MR portography, with flexible time window and high vascular signals. This imaging may allow for other post‐contrast imaging options before portography and release patients from consecutive breath‐holds. J. Magn. Reson. Imaging 2004;19:238–244. © 2004 Wiley‐Liss, Inc.
Blood oxygenation level‐dependent MRI of cerebral gliomas during breath holding
Authors: Hsu Yuan‐Yu , Chang Chen‐Nen , Jung Shih‐Ming , Lim Kun‐Eng , Huang Ju‐Chuan , Fang Shin‐Yi , Liu Ho‐Ling
Published: January 2004

Purpose

To assess the cerebrovascular responses to short breath holding of cerebral gliomas using blood oxygenation level‐dependent (BOLD) magnetic resonance imaging (MRI).

Materials and Methods

Six patients with a low‐grade glioma and one patient with a high‐grade glioma were studied using T2*‐weighted echo planar imaging (EPI) during repeated periods of 15‐second or 20‐second breath‐holding. Tumor vascularity was evaluated using dynamic susceptibility contrast perfusion MRI.

Results

Increases in BOLD signal intensity during repeated breath‐holding were consistently identified in patients' normal appearing gray matter, comparable with those in healthy adults. Absence of significant BOLD signal enhancement was noted both in low‐grade and high‐grade gliomas, which is either due to overwhelming hypoxia in a tumor, inadequacy or absence of hypercapnia‐induced vasodilatation of tumor vessels, or both. Breath‐hold regulated decreases in BOLD signals occurred only in the high‐grade glioma, which is most likely due to the hypercapnia‐induced steal effect that redistributes blood flow from tumor regions with unresponsive neovasculature to surrounding normal tissue.

Conclusion

BOLD MRI during short breath holding can disclose differential cerebrovascular response between normal tissue and cerebral glioma. J. Magn. Reson. Imaging 2004;19:160–167. © 2004 Wiley‐Liss, Inc.
MR flow mapping of dobutamine‐induced changes in diastolic heart function
Authors: Paelinck Bernard P. , Lamb Hildo J. , Bax Jeroen J. , van der Wall Ernst E. , de Roos Albert
Published: January 2004

Purpose

To evaluate the ability of MR flow mapping to measure changes in left ventricular filling during β‐adrenergic stimulation.

Materials and Methods

Mitral flow was measured in 10 healthy volunteers using conventional free breathing fast‐field echo (FFE) with a spatial resolution of 2.7 × 2.2 mm and a temporal resolution of 22 msec. The sequence was repeated during dobutamine infusion (20 μg/kg/minute).

Results

Stroke volume increased from a median of 99 mL (range: 68–142 mL) (Note: values as presented are medians and ranges, throughout) to 114 mL (87–180 mL) (P < 0.05). Both early (E) peak filling rate (554 mL/second [433–497 mL] to 651 mL/second [496–1096 mL/second]) (P < 0.05) and atrial (A) peak filling rate (238 mL/second [183–352 mL/second] to 341 mL/second [230–538 mL/second]) (P < 0.05) increased. These changes, together with the increase in E acceleration peak and A deceleration peak, were consistent with facilitated myocardial relaxation.

Conclusion

Conventional free breathing FFE has the ability to measure the effects of β‐adrenergic stimulation on left ventricular filling. J. Magn. Reson. Imaging 2004;19:176–181. © 2004 Wiley‐Liss, Inc.
A method for preamplifier‐decoupling improvement in quadrature phased‐array coils
Authors: Guclu Ceylan Celil , Boskamp Ed , Zheng Tsinghua , Becerra Ricardo , Blawat LeRoy
Published: January 2004

Purpose

To improve preamplifier decoupling in a quadrature phased‐array coil using a new quadrature combiner configuration.

Materials and Methods

A commercial six‐element quadrature cervical‐thoracic‐lumbar (CTL) coil was used on a 1.5 T GE Signa Lx Scanner. The new combiner configuration is designed based on the fact that when one compares the amount of flux linkage of two loops with butterfly elements separated by the same distance, the loop elements have much higher coupling than the butterfly elements.

Results

The results are demonstrated using an imaging‐based element coupling measurement method. The new quadrature combiner configuration has introduced an approximately −8dB improvement in preamplifier decoupling.

Conclusion

One‐dimensional quadrature phased arrays can be built even if the preamplifier is not integrated in the coil. If the combiner is placed between the coil and the preamplifiers, the butterflies should be on the high impedance side of the quadrature combiner. The loops should see the low input impedance of the preamplifiers. J. Magn. Reson. Imaging 2004;19:255–258. © 2004 Wiley‐Liss, Inc.
Automatic model‐based evaluation of magnetic resonance‐guided radio frequency ablation lesions with histological correlation
Authors: Lazebnik Roee S. , Breen Michael S. , Lewin Jonathan S. , Wilson David L.
Published: January 2004

Purpose

To develop a model‐based method for automatic evaluation of radio frequency (RF) ablation treatment using magnetic resonance (MR) images.

Materials and Methods

RF current lesions were generated in a rabbit thigh model using MR imaging (MRI) guidance. We created a 12‐parameter, three‐dimensional, globally deformable model with quadric surfaces that delineates lesion boundaries and is automatically fitted to MR grayscale data. We applied this method to in vivo T2‐ and contrast‐enhanced (CE) T1‐weighted MR images acquired immediately post‐ablation and four days later. We then compared results to manually segmented MR and three‐dimensional registered corresponding histological boundaries of cellular damage.

Results

Resulting lesions featured a two‐boundary appearance with an inner region and an outer hyperintense margin on MR images. For automated vs. manual MR boundaries, the mean errors over all specimens were 0.19 ± 0.51 mm and 0.27 ± 0.52 mm for the inner surface, and −0.29 ± 0.40 mm and −0.12 ± 0.17 mm for the outer surface, for T2‐ and CE T1‐weighted images, respectively. For automated vs. histological boundaries, mean errors over all specimens were 0.07 ± 0.64 mm and 0.33 ± 0.71 mm for the inner surface, and −0.27 ± 0.69 mm and 0.02 ± 0.43 mm for the outer surface, for T2‐ and CE T1‐weighted images, respectively. All boundary errors compared favorably to MR voxel dimensions, which were 0.7 mm in‐plane and 3.0 mm thick.

Conclusion

The method is accurate both in describing MR‐apparent boundaries and in predicting histological response and has applications in lesion visualization, volume estimation, and treatment evaluation. J. Magn. Reson. Imaging 2004;19:245–254. © 2004 Wiley‐Liss, Inc.
K‐space in the clinic
Authors: Paschal Cynthia B. , Morris H. Douglas
Published: January 2004

Magnetic resonance imaging (MRI) sequences are characterized by both radio frequency (RF) pulses and time‐varying gradient magnetic fields. The RF pulses manipulate the alignment of the resonant nuclei and thereby generate a measurable signal. The gradient fields spatially encode the signals so that those arising from one location in an excited slice of tissue may be distinguished from those arising in another location. These signals are collected and mapped into an array called k‐space that represents the spatial frequency content of the imaged object. Spatial frequencies indicate how rapidly an image feature changes over a given distance. It is the action of the gradient fields that determines where in the k‐space array each data point is located, with the order in which k‐space points are acquired being described by the k‐space trajectory. How signals are mapped into k‐space determines much of the spatial, temporal, and contrast resolution of the resulting images and scan duration. The objective of this article is to provide an understanding of k‐space as is needed to better understand basic research in MRI and to make well‐informed decisions about clinical protocols. Four major classes of trajectories—echo planar imaging (EPI), standard (non‐EPI) rectilinear, radial, and spiral—are explained. Parallel imaging techniques SMASH (simultaneous acquisition of spatial harmonics) and SENSE (sensitivity encoding) are also described. J. Magn. Reson. Imaging 2004;19:145–159. Published 2004 Wiley‐Liss, Inc.
Bone marrow diffusion in osteoporosis: Evaluation with quantitative MR diffusion imaging
Authors: Yeung David K. W. , Wong Samuel Y.S. , Griffith James F. , Lau Edith M.C.
Published: January 2004

Purpose

To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects.

Materials and Methods

A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x‐ray absorptiometry (T‐score) and 20 normal subjects (mean age, 28 years) were examined with echo‐planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared.

Results

Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 ± 0.12 × 10–3 mm2/second) than normal premenopausal women (0.50 ± 0.09 × 10–3 mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 ± 0.10 × 10–3 mm2/second) and normal BMD (0.43 ± 0.08 × 10–3 mm2/second) compared to normal controls (0.49 ± 0.07 × 10–3 mm2/second).

Conclusion

Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis. J. Magn. Reson. Imaging 2004;19:222–228. © 2004 Wiley‐Liss, Inc.
Assessment of motion gating strategies for mouse magnetic resonance at high magnetic fields
Authors: Cassidy Paul J. , Schneider Jürgen E. , Grieve Stuart M. , Lygate Craig , Neubauer Stefan , Clarke Kieran
Published: January 2004

Purpose

To assess the performance of motion gating strategies for mouse cardiac magnetic resonance (MR) at high magnetic fields by quantifying the levels of motion artifact observed in images and spectra in vivo.

Materials and Methods

MR imaging (MRI) of the heart, diaphragm, and liver; MR angiography of the aortic arch; and slice‐selective 1H‐spectroscopy of the heart were performed on anesthetized C57Bl/6 mice at 11.75 T. Gating signals were derived using a custom‐built physiological motion gating device, and the gating strategies considered were no gating, cardiac gating, conventional gating (i.e., blanking during respiration), automatic gating, and user‐defined gating. Both automatic and user‐defined modes used cardiac and respiratory gating with steady‐state maintenance during respiration. Gating performance was assessed by quantifying the levels of motion artifact observed in images and the degree of amplitude and phase stability in spectra.

Results

User‐defined gating with steady‐state maintenance during respiration gave the best performance for mouse cardiac imaging, angiography, and spectroscopy, with a threefold increase in signal intensity and a sixfold reduction in noise intensity compared to cardiac gating only.

Conclusion

Physiological gating with steady‐state maintenance during respiration is essential for mouse cardiac MR at high magnetic fields. J. Magn. Reson. Imaging 2004;19:229–237. © 2004 Wiley‐Liss, Inc.
MR colonography: How does air compare to water for colonic distention?
Authors: Ajaj Waleed , Lauenstein Thomas C. , Pelster Gregor , Goehde Susanne C. , Debatin Joerg F. , Ruehm Stefan G.
Published: January 2004

Purpose

To prove the feasibility of air‐distended magnetic resonance colonography (MRC) and compare it with water‐based distention.

Materials and Methods

In five volunteers, the colon was imaged twice: once after distending the colon with air and a second time after distending the colon with water. A total of 50 patients, who had been referred to colonoscopy for a suspected colorectal pathology were randomized into water‐distention (N = 25) and air‐distention (N = 25) groups. A contrast‐enhanced T1‐weighted three‐dimensional volume interpolated breath‐hold (VIBE) sequence was collected. Comparative analysis was based on qualitative ratings of image quality and bowel distention, as well as contrast‐to‐noise ratio (CNR) measurements for the colonic wall with respect to the colonic lumen. In addition, patient acceptance was evaluated.

Results

Inflammatory changes and colorectal masses were correctly identified on MRC in eight patients each. One 4‐mm polyp identified at colonoscopy was missed on water‐distended MRC. There were no false positive findings. No significant differences were found between air‐ and water‐distention regarding discomfort levels and image quality. The presence of air in the colonic lumen was not associated with susceptibility artifacts. CNR of the contrast‐enhanced colonic wall, as well as bowel distention, were superior on air‐distended three‐dimensional data sets.

Conclusion

MRC can be performed using either water or air for colonic distention. Both techniques permit assessment of the colonic wall and identification of colorectal masses. While discomfort levels are similar for both agents, MRC with air provides higher CNR and better colonic distention. J. Magn. Reson. Imaging 2004;19:216–221. © 2004 Wiley‐Liss, Inc.
Activation of neural pathways associated with sexual arousal in non‐human primates
Authors: Ferris Craig F. , Snowdon Charles T. , King Jean A. , Sullivan John M. , Ziegler Toni E. , Olson David P. , Schultz‐Darken Nancy J. , Tannenbaum Pamela L. , Ludwig Reinhold , Wu Ziji , Einspanier Almuth , Vaughan J. Thomas , Duong Timothy Q.
Published: January 2004

Purpose

To evaluate brain activity associated with sexual arousal, fully conscious male marmoset monkeys were imaged during presentation of odors that naturally elicit high levels of sexual activity and sexual motivation.

Material and Methods

Male monkeys were lightly anesthetized, secured in a head and body restrainer with a built‐in birdcage resonator and positioned in a 9.4‐Tesla spectrometer. When fully conscious, monkeys were presented with the odors of a novel receptive female or an ovariectomized monkey. Both odors were presented during an imaging trial and the presentation of odors was counterbalanced. Significant changes in both positive and negative BOLD signal were mapped and averaged.

Results

Periovulatory odors significantly increased positive BOLD signal in several cortical areas: the striatum, hippocampus, septum, periaqueductal gray, and cerebellum, in comparison with odors from ovariectomized monkeys. Conversely, negative BOLD signal was significantly increased in the temporal cortex, cingulate cortex, putamen, hippocampus, substantia nigra, medial preoptic area, and cerebellum with presentation of odors from ovariectomized marmosets as compared to periovulatory odors. A common neural circuit comprising the temporal and cin‐gulate cortices, putamen, hippocampus, medial preoptic area, and cerebellum shared both the positive BOLD response to periovulatory odors and the negative BOLD response to odors of ovariectomized females.

Conclusion

These data suggest the odor‐driven enhancement and suppression of sexual arousal affect neuronal activity in many of the same general brain areas. These areas included not only those associated with sexual activity, but also areas involved in emotional processing and reward. J. Magn. Reson. Imaging 2004;19:168–175. © 2004 Wiley‐Liss, Inc.
Mucosal arenavirus infection of primates can protect them from lethal hemorrhagic fever
Authors: Rodas Juan D. , Lukashevich Igor S. , Zapata Juan C. , Cairo Cristiana , Tikhonov Ilia , Djavani Mahmoud , Pauza C. David , Salvato Maria S.
Published: January 2004

Arenaviruses are transmitted from rodents to human beings by blood or mucosal exposure. The most devastating arenavirus in terms of human disease is Lassa fever virus, causing up to 300,000 annual infections in West Africa. We used a model for Lassa fever in which Rhesus macaques were infected with a related virus, lymphocytic choriomeningitis virus (LCMV). Our goals were to determine the outcome of infection after mucosal inoculation and later lethal challenge, to characterize protective immune responses, and to test cross‐protection between a virulent (LCMV‐WE) and an avirulent (LCMV‐ARM) strain of virus. Although intravenous infections in the monkey model were uniformly lethal, intragastric infections recapitulated the spectrum of clinical outcomes seen in human exposure to Lassa fever virus: death, recovery from disease, and most often, subclinical infection. Plaque neutralization, ELISA, lymphocyte proliferation, and chromium‐release assays were used to monitor humoral and cellular immune responses. Cross protection between the two strains was observed. The three out of seven monkeys that experienced protection were also the three with the strongest cell‐mediated immunity. J. Med. Virol. 72:424–435, 2004. © 2004 Wiley‐Liss, Inc.
Mechanisms of beta cell death during restricted and unrestricted enterovirus infection
Authors: Rasilainen Suvi , Ylipaasto Petri , Roivainen Merja , Bouwens Luc , Lapatto Risto , Hovi Tapani , Otonkoski Timo
Published: January 2004

Coxsackie B virus (CVB‐5) infections potentially trigger and accelerate pancreatic beta cell damage leading to type 1 diabetes. In vivo, all viruses face natural resistance mediated by various host factors which restrict the progression of infection. Thus, the aims of this study were to generate a tissue culture model of restricted coxsackie B virus infection in primary islet cells by preventing the production of viral progeny with a selective inhibitor of viral RNA replication and to investigate the mechanisms of virus‐induced islet cell death during productive and restricted infective conditions. Cultured foetal porcine islet cells were infected effectively with the prototype strain of coxsackievirus B5 (CVB‐5). Nuclear viability stainings and electron microscopy showed productive infection to result in dominantly necrotic cell death with additional slight induction of apoptosis during the 7 days of follow‐up. The restricted conditions were created by addition of guanidine–hydrochloride (G–HCl) into culture medium. At 1 mM concentration, it significantly protected the infected cells from necrosis and thus maintained high viability. This was associated with increased significantly apoptosis. In perifusion analysis, the cellular ability to release insulin was reduced, although the metabolic integrity was preserved as shown by MTT‐analysis and cellular ATP levels. These data show that restriction of CVB‐5 replication with G–HCl protects islet cells against virus‐induced necrosis. However, restriction of viral replication shifts the mechanism of cell death from necrosis toward apoptosis. A slowly progressing subclinical infection of islets could thus lead to increased beta‐cell apoptosis. J. Med. Virol. 72:451–461, 2004. © 2004 Wiley‐Liss, Inc.
Apoptosis in dengue virus infected liver cell lines HepG2 and Hep3B
Authors: Thongtan Thananya , Panyim Sakol , Smith Duncan R.
Published: January 2004

While both in vivo and in vitro evidence has suggested that liver cells undergo apoptosis in response to dengue virus infection, little is known about the mechanism of induction. Given that the p53 tumour suppressor gene is a key mediator of apoptosis, we sought to define the role of this gene in response to dengue virus infection. After infection, a p53 wild type liver cell line (HepG2) showed changes consistent with apoptosis including alterations of cell morphology, cellular detachment and DNA laddering. However, p53 was neither up‐regulated, nor showed any evidence of complexing with dengue virus proteins as determined by immunoprecipitation. Infection of a p53 null liver cell line (Hep3B) also produced changes consistent with the induction of apoptosis. While the profile of the cells undergoing apoptosis in each cell line was similar as determined by flow cytometry, the absolute levels were markedly different with up to 90% of Hep3B cells undergoing apoptosis compared to only 20% of HepG2 cells at day 5 post infection. By day 7, all Hep3B infected cells were dead. In contrast, it proved possible to culture dengue virus infected HepG2 cells for 3 months. Viral progeny released from the p53 null cell line were nine‐fold higher per attached cell than from the p53 wild type cell line. These results suggest that, while induction of apoptosis in liver cells is mediated by a non‐p53 regulated pathway, p53 may play a role in restricting the level of viral progeny to below a critical level at which apoptosis is triggered. J. Med. Virol. 72:436–444, 2004. © 2004 Wiley‐Liss, Inc.