bluuebunny/crossref_metadata_2025 huggingface dataset:
Zanthoxylum piperitum (DC), a potential feeding deterrent for mammals: studies with Microtus ochrogaster (Wagner)
Authors: Epple Gisela , Bryant Bruce P. , Mezine Igor , Lewis Stanley
Published: April 2004

Total extract from the fruit of Szechuan pepper (Zanthoxylum piperitum DC), the volatile components of the extract and a non‐volatile fraction containing alkylamides (NVA fraction) are feeding deterrents for rats. The present study investigated the effectiveness of these natural repellents in prairie voles (Microtus ochrogaster Wagner). Two‐choice feeding trials were conducted during which food‐deprived voles were offered choices between oat‐bran wafers. In Experiment 1, 10 voles were given three sets of feeding trials, each 2 h long. Baseline consumption was established during the first set of two trials by offering a choice between two oat‐bran wafers dipped in ethanol, the control solvent. During the second set of two trials the voles were given a choice between an oat‐bran wafer dipped in ethanol and a wafer dipped in Zanthoxylum extract. During the third set the voles were given a choice between a wafer served on top of a screened dish containing a sample of ethanol and a wafer served on top of a dish containing a sample of extract. In this manner the voles were exposed to volatile compounds emanating from the extract but could not contact it. Wafers dipped in extract were almost completely avoided. The volatile components of extract also significantly reduced food intake. In Experiment 2, habituation to the volatile constituents of extract was examined in 16 Zanthoxylum‐naïve voles. Baseline consumption was established by offering two wafers served on top of screened dishes containing ethanol. This was followed by twelve tests during which a choice between a wafer served above a sample of ethanol and a wafer served above a sample of extract was given. The voles failed to habituate to the volatile components of extract, consistently consuming less of the wafers served above extract. In Experiment 3 a dose‐response curve to Zanthoxylum extract was established, using 12 stimulus‐naïve voles. After baseline consumption was established, the animals were given two tests each, presenting a choice between a control wafer and a wafer dipped in a dilution of extract (0.001–100 g liter−1). Only concentrations of 10 and 100 g liter−1 reduced food intake. In Experiment 4 the effects of the non‐volatile fraction of extract were compared to those of whole extract. Vegetable oil was used as solvent. Eight stimulus‐naïve voles were given two tests with a choice between an oil‐dipped and an extract‐dipped wafer. A second group of eight voles received two tests with a choice between an oil‐dipped and NVA‐dipped wafer. Extract‐dipped wafers were avoided, but the NVA fraction had no effect on food consumption. Copyright © 2004 Society of Chemical Industry
Effect of humanin analogues on experimentally induced impairment of spatial memory in rats
Authors: Krejcova Gabriela , Patocka Jiri , Slaninova Jirina
Published: April 2004

Humanin and its analogues have been shown to protect cells against death induced by various Alzheimer's disease genes and amyloid‐β‐peptides in vitro; the analogue [Gly14]‐humanin has also been shown to be potent in reversing learning and memory impairment induced by scopolamine in mice in vivo. It is important to validate these results by using other behavioral methods. In this study, the effect of [Gly14]‐humanin and des‐Leu‐PAGA, another analogue (0.2 µmol kg−1, i.p.) on the 3‐quinuclidinyl benzilate‐induced (2 mg kg−1, i.p.) impairment of spatial memory in the multiple T‐maze in rats has been evaluated. Both peptides reversed the impairment of spatial memory. These results indicate the potential of humanin analogues in modulation of the cholinergic system. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
High‐yield, solid‐phase synthesis of humanin, an Alzheimer's disease associated, novel 24‐mer peptide which contains a difficult sequence
Authors: Evangelou Alexandra , Zikos Christos , Livaniou Evangelia , Evangelatos Gregory P.
Published: April 2004

Humanin is a novel, 24‐mer residue bioactive peptide, which antagonizes Alzheimer's disease (AD) related neurotoxicity and offers a hope for developing new therapeutics against AD. Access to adequate amounts of pure humanin is a prerequisite for further, thorough, investigation of the pharmacological properties and therapeutic potency of the peptide. Until now, humanin has been obtained mainly by molecular biology techniques. In this work the Fmoc solid‐phase synthesis of humanin on an in‐house prepared 2‐Cl‐tritylamidomethyl polystyrene resin is described fully. Special precautions, i.e. prolonged deprotection steps, should be taken to achieve a high overall yield, since humanin seems to contain a ‘difficult sequence’ (R4G5F6S7C8L9) near its highly lipophilic, biologically important region L9L10L11L12. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Are language‐based activities in science effective for all students, including low achievers?
Authors: Rivard Léonard P.
Published: April 2004

The study investigated achievement status as a factor determining the use of language‐based activities for learning science. A total of 154 eighth‐grade students were randomly assigned to four groups, all stratified for gender and achievement level. The treatments involved various combinations of talk and writing, and descriptive and explanatory tasks. The dependent measures included scores on multiple choice tests obtained at three times during the study. Records of student talk and writing were also analyzed to identify patterns of differences between groups of achievers. The findings suggested that low achievers complete more problems, and develop better understanding and comprehension of ecology concepts when they have engaged in peer discussions of explanatory tasks. In comparison, high achievers benefit more from writing than talking, and writing explanations enhances comprehension more than restricted writing activities. © 2004 Wiley Periodicals, Inc. Sci Ed 88:420–442, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.sce10114
Difficulties in learning the introductory magnetic field theory in the first years of university
Authors: Guisasola Jenaro , Almudí José M. , Zubimendi José L.
Published: April 2004

This study examined university engineering and physical science students' misconceptions of the nature of magnetic field. It is assumed that a significant knowledge of the sources of magnetic field is a basic prerequisite when students have to think about electromagnetic phenomena. To analyze students' conceptions, we have taken into account the fact that individuals build mental representations to help them understand the functioning of a physical system. These mental representations include different explanatory categories of reality in one same individual, depending on the context and the contents concerned. Therefore, we have designed an interview and an open‐question questionnaire with an emphasis on explanations, so as to analyze the students' reasoning. We found that most of the students failed to identify the source of the magnetic field and they confuse magnetic force and magnetic field. It is concluded that although the questionnaire and interviews involved a wide range of phenomena, the misconceptions identified fall into four main categories of explanations which can inform curriculum development by identifying the strengths and weaknesses of the students' conceptions. © 2004 Wiley Periodicals, Inc. Sci Ed 88:443–464, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.sce10119
Using concept mapping for assessing and promoting relational conceptual change in science
Authors: Liu Xiufeng
Published: April 2004

In this article, we adopted the relational conceptual change as our theoretical framework to accommodate current views of conceptual change such as ontological beliefs, epistemological commitment, and social/affective contexts commonly mentioned in the literature. We used a specific concept mapping format and process—digraphs and digraphing—as an operational framework for assessing and promoting relational conceptual change. We wanted to find out how concept mapping can be used to account for relational conceptual change. We collected data from a Grade 12 chemistry class using collaborative computerized concept mapping on an ongoing basis during a unit of instruction. Analysis of progressive concept maps and interview transcripts of representative students and the teacher showed that ongoing and collaborative computerized concept mapping is able to account for student conceptual change in ontological, epistemological, and social/affective domains. © 2004 Wiley Periodicals, Inc. Sci Ed 88:373–396, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.sce10127
PEXIS: Probabilistic experience representation based adaptive interaction system for personal robots
Authors: Inamura Tetsunari , Inaba Masayuki , Inoue Hirochika
Published: April 2004

In this paper the authors focus on the interaction between users and personal robots that can move in a real environment. When the creation of robots that can perform in an ordinary home or office is considered, it is difficult to imagine beforehand what kind of environment will be used, and so the approach in which developers embed environmental knowledge and strategies for autonomous movement fails. Thus, the authors propose an approach in which knowledge of the environment and the knowledge needed to move are acquired after development by allowing the robot and the user who is using the robot to engage in dialogue, and representing experience statistically. The authors introduce PEXIS, an interaction system developed using this approach, and then describe the characteristics and utility of their system via examples such as learning to avoid objects in an office environment and adapting to the vocabulary expressions of a particular user. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 98–109, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10034
Transformation from population codes to firing rate codes by learning: Neural representation of smooth pursuit eye movements
Authors: Taguchi Shinya , Tabata Hiromitsu , Shibata Tomohiro , Kawato Mitsuo
Published: April 2004

It has been reported that not only the information related to retinal slip but also the non‐visual information were population‐coded in the middle temporal (MT) area and the medial superior temporal (MST) area during smooth pursuit eye movements. On the other hand, it has been also reported that the information related to motor signals to generate eye movements were firing rate‐coded in the Purkinje cells in the cerebellum. Here, we propose a computational model of smooth pursuit that includes various temporal patterns of neural firing in the MT/MST areas and synaptic plasticity in the cerebellar cortex. We show that the signals to generate smooth pursuit eye movements could be extracted from the signals population‐coded in the cerebral cortex by means of the synaptic plasticity in the cerebellar cortex. Our results indicate that the transformation from population codes to firing rate‐codes occurs in the cerebellum during smooth pursuit eye movements © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 79–88, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10322
An implementation method of automatic metadata extraction method for music data and its application to semantic associative search
Authors: Kitagawa Takashi , Nakanishi Takafumi , Kiyoki Yasushi
Published: April 2004

In this paper, we present a method for implementing a Kansei (sensitivity) operator for an automatic metadata extraction method used for media data. The Kansei operator, which operates on metadata extracted from media data, performs mapping based on human sensitivity by applying a logarithmic function that reflects human sensitivity based on Fechner's law. The proposed method enables metadata that reflects human sensitivity to be extracted according to the Kansei operator for metadata that was obtained according to weighted word categories output by a conventional automatic metadata extraction method. In addition, using a semantic associative search method enables searching to be performed, which matches human intuition for the media data categories. In this paper, we combine the Kansei operator with an automatic metadata extraction method for music data to implement an automatic metadata extraction method having a Kansei operator for music data. In addition, they show the effectiveness of the proposed method experimentally. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 59–78, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10380
Partial matching accuracy indices for shapes
Authors: Fukushima Shigehiro , Zheng Zi‐Liuk , Yoshinaga Yukiyasu
Published: April 2004

Indices are proposed to measure the partial matching accuracy for outlines of shapes such as those identified only partially due to occlusion and with limited region of interest. The figure catching rate and the partial matching rate curves are defined. The fractional area under the curve represents effectively the matching accuracy. More intuitive indices are the catching and matching distances. The indices are illustrated with an example of application to evaluation of gastric outlines recognized in double‐contrast gastric radiograms. Gastric regions delineated by a computer are compared with tracings by a radiologist, in an attempt to evaluate numerically the accuracy. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 50–58, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10550
Evaluation of criteria on information retrieval
Authors: Ishioka Tsunenori
Published: April 2004

We investigate van Rijsbergen'sF‐measure, the break‐even point, and 11‐point averaged precision, all of which can be translated into one‐dimensional scalar quantities from the precision and the recall. These investigations can be done by comparing to the tetrachoric (four‐fold) correlation coefficient and phi (four‐fold point) coefficient, which are often used as indices of statistical association in a 2 × 2 contingency table. The results show that when the fallout rate is less than 0.1,

theF1measure has similar properties to the phi coefficient,

the break‐even point is almost equivalent to the phi coefficient, and

the 11‐point averaged precision should be a measure which is larger than the phi coefficient and smaller than a tetrachoric correlation coefficient.

© 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 42–49, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10583
For geometric inference from images, what kind of statistical model is necessary?
Authors: Kanatani Kenichi
Published: April 2004

In order to promote mutual understanding with researchers in other fields including statistics, this paper investigates the meaning ofstatistical methodsfor geometric inference based on image feature points. We trace back the origin of feature uncertainty to image processing operations and discuss the meaning ofgeometric fitting, geometric model selection, thegeometric AIC, and thegeometric MDL. Then, we discuss the implications of asymptotic analysis in reference tonuisance parameters, theNeyman‐Scott problem, andsemiparametric modelsand point out that application of statistical methods requires careful considerations about the peculiar nature of geometric inference. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(6): 1–9, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10635
The ‘Fishing License’ method for analysing the time course of effects in repeated measurements
Authors: Nadziejko Christine , Chi Chen Lung , Nádas Arthur , Hwang Jing‐Shiang
Published: April 2004

Inference on the time of onset and the duration of a treatment effect is a challenging problem in biomedical research. These studies often generate repeated measurements from subjects in a treated group and a control group during the same time period. We propose a simple approach, called the ‘Fishing License’ method, to test for a treatment effect occurring during an unspecified time interval. The method is based on a statistic of the largest absolute value of the t statistic between two groups obtained by considering every possible time interval in the observed time period. A bootstrapped null distribution of the test statistic is used to determine the critical value. The method also provides estimates of onset and ending times, when the null hypothesis of no effect is rejected. Simulated and real experimental data sets were generated for assessing the performance of the method. Copyright © 2004 John Wiley & Sons, Ltd.
Construction of group sequential designs in clinical trials on the basis of detectable treatment differences
Authors: Schäfer Helmut , Müller Hans‐Helge
Published: April 2004

The treatment effect sizes that can be detected with sufficient power up to the different interim analyses constitute a clinically meaningful criterion for the selection of a group sequential test for a clinical trial. For any pre‐specified sequence of effect sizes, it is possible to construct group sequential boundaries such that the trial has a pre‐specified power to reject the null‐hypothesis at or before the corresponding interim analysis under the respective treatment effect. The principle of constructing group sequential designs on the basis of detectable treatment effects is presented. The application in common situations such as two‐armed trials with continuous or binary outcome or censored survival times is described. We also present an effective algorithm. Copyright © 2004 John Wiley & Sons, Ltd.
Relationship between a traumatic life event and an alteration in stress response
Authors: Izutsu Takashi , Tsutsumi Atsuro , Asukai Nozomu , Kurita Hiroshi , Kawamura Noriyuki
Published: April 2004

An Erratum has been published for this article in Stress and Health 20(5) 2004, 309.

The relationship between past traumatic experience and stress tolerance is poorly understood. To investigate the relationship among past exposure to trauma, stress tolerance and other mental health indexes, experience of traumatic events, depression, anxiety, and job strain were assessed in 2959 male and 279 female workers. Job strain was used as an indicator of stress tolerance in this study. Past traumatic experience was shown to increase later anxiety for both sexes, and increase depression and job strain in male subjects. For the first time, people with past traumatic experiences were found to feel a stressor's influence more strongly. Further, those influences differed according to the type of past trauma. The existence of interactions among the experience of traumatic events, depression/anxiety, and strain indicated that stress tolerance seemed to be an important element in the trauma response mechanism. Copyright © 2004 John Wiley & Sons, Ltd.
The diversity among us: Puerto Ricans, Cuban Americans, Caribbean Americans, and Central and South Americans
Authors: Torres Vasti
Published: April 2004

Research on Latino college students is largely based on the experiences of Mexican Americans. In this chapter, diverse experiences of other groups in terms of immigration, educational achievement, and economic attainment are highlighted, and implications for student services are explored.
Latinos at community colleges
Authors: Martinez Magadelena , Fernández Edith
Published: April 2004

Community colleges serve as the point of entry for the majority of Latinos in higher education, offering low‐cost, smaller‐scale educational opportunities in the communities where students live and providing the preparation for four‐year colleges and universities that may have been lacking in their K–12 education. The challenges to community colleges in providing services to Latinos are great, but their potential to facilitate the achievement of Latinos is vast.
The interobserver reliability of three‐dimensional power Doppler data acquisition within the female pelvis
Authors: Raine‐Fenning N. J. , Campbell B. K. , Clewes J. S. , Kendall N. R. , Johnson I. R.
Published: April 2004

Objectives

To examine the interobserver reliability of three‐dimensional (3D) power Doppler data acquisition from the uterus and ovary.

Methods

3D power Doppler angiography was used to acquire endometrial data from 20 patients and ovarian data from a further 20 different patients at various stages of in vitro fertilization. Two different observers each acquired two datasets from all 40 patients resulting in 80 endometrial and 80 ovarian datasets in total. Virtual Organ Computer‐aided AnaLysis was used to define the object of interest and semiquantify the power Doppler signal within it. The reliability of measurements of volume and vascularity was assessed by calculating interclass correlation coefficients (ICCs) and limits of agreement between the two observers.

Results

Whilst volumetric data proved more reliably acquirable than power Doppler data, the interobserver reliability of data acquisition was high overall for both the endometrium and ovary with all measurements obtaining a lower ICC of above 0.9. Limits of agreement revealed minimal disagreement between the two observers for measurements of volume and vascularity within both the ovary and endometrium. The ‘indices of vascularity’ within the endometrium were less than those derived from the ovary and subendometrium, which were comparable.

Conclusions

3D ultrasound can be reliably used between observers to acquire power Doppler information from the ovary and endometrium thus supporting the current use and further development of this technique in clinical practice. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Idiopathic constriction of the fetal ductus arteriosus
Authors: Trevett T. N. , Cotton J.
Published: April 2004

Constriction of the ductus arteriosus in the fetus is well studied, but mostly secondary to maternal exposure to indomethacin or other non‐steroidal anti‐inflammatory medications, or structural cardiac lesions. We present a case of a fetus presenting with right ventricular hypertrophy secondary to an S‐shaped ductus arteriosus with distal constriction diagnosed by pulsed Doppler imaging. A review of the recent English literature of similar cases is presented. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Robust Hurwitz stability of a class of complex polynomials arising from H∞ control theory
Authors: Wang Z.H.
Published: April 2004

This paper deals with the Hurwitz stability of a class of complex polynomials arising from H∞ control theory. Using an isomorphic transformation between the complex variables, sufficient and necessary conditions are obtained on the basis of the Sylvester resultant. Moreover, by applying the complete discrimination system for real polynomials, algebraic criteria for the Hurwitz stability can be derived easily. Unlike the known methods with which the stability test involves infinitely many testing steps, our method provides a testing procedure that needs only a finite number of testing steps. As an application, the presented method has been used successfully to study the problem of H∞ Hurwitz stabilization, a problem of simultaneous stabilization of the closed‐loop characteristic polynomial, and a family of complex polynomials of our concern.
Exact 2D piezoelasticity solution of hybrid beam with damping under harmonic electromechanical load
Authors: Kapuria S. , Dumir P.C. , Ahmed A.
Published: April 2004

Two dimensional piezoelasticity solution is presented for steady state forced response of simply supported hybrid beams with embedded or surface bonded piezoelectric layers under electromechanical harmonic excitation with damping. For each layer, all entities are expanded in Fourier series to satisfy the boundary conditions at the ends. The governing equations reduce to ordinary differential equations in the thickness coordinate with constant coefficients. Their general solution for each layer involves six arbitrary constants. A transfer matrix approach is presented to obtain these from the electromechanical conditions at the top and bottom of the beam, the conditions of prescribed potentials at the interfaces with piezoelectric layers, and the conditions of continuity/jump at the layer interfaces. Results for the amplitude and phase lag of the deflection are presented for composite, sandwich, and hybrid beams. The reduction of deflection response by actuation of a piezoelectric layer is illustrated. The present benchmark solution would help to assess 1D beam theories for damped response under harmonic loads.
Sun‐coupled climate connection between eastern Asia and northern Atlantic
Authors: Tan Ming , Hou Juzhi , Liu Tungsheng
Published: April 2004

Few of annually resolved proxy temperature records are reported to coincide with centennial‐to‐millennial‐scale solar oscillations. Here we show that the warm season temperature inferred from the layer thickness of a stalagmite from Beijing in Eastern Asia is consistent with oscillations in total solar irradiance inferred from cosmogenic 10Be and 14C. On the other hand, this climate record is remarkably consistent with Northern Atlantic drift ice cycles that were identified to be controlled by the sun through the entire Holocene. The synchronism between the two independent sun‐linked climate records therefore suggests that the sun may directly couple hemispherical climate changes on centennial to millennial scales.
Comparison of the Odin/OSIRIS stratospheric ozone profiles with coincident POAM III and ozonesonde measurements
Authors: Petelina S. V. , Llewellyn E. J. , Degenstein D. A. , Lloyd N. D. , Gattinger R. L. , Haley C. S. , von Savigny C. , Griffioen E. , McDade I. C. , Evans W. F. J. , Murtagh D. P. , de La Noe J.
Published: April 2004

We present first statistical comparison results for stratospheric ozone density profiles retrieved from Odin/OSIRIS limb scattered radiance with 1220 coincident POAM III and 205 coincident ozonesonde measurements. Profiles are compared on a monthly basis from November 2001 to October 2002. Most of the time, differences between OSIRIS mean profiles and those measured by POAM III and ozonesondes were 5–7% between 15 km and 32 km, and within 15% above 32 km. In April–July 2002, OSIRIS mean profiles appear shifted downward by ∼1 km, introducing a difference of about 10% with POAM III and about 25% with ozonesonde profiles between 15 km and 32 km. This study demonstrates that outside the April–July 2002 period, the OSIRIS ozone profiles agree well with coincident ozonesonde and POAM III ozone profiles and make a valuable addition to the international ozone database available for research into global ozone change.
Controls on tectonic accretion versus erosion in subduction zones: Implications for the origin and recycling of the continental crust
Authors: Clift Peter , Vannucchi Paola
Published: April 2004

Documenting the mass flux through convergent plate margins is important to the understanding of petrogenesis in arc settings and to the origin of the continental crust, since subduction zones are the only major routes by which material extracted from the mantle can be returned to great depths within the Earth. Despite their significance, there has been a tendency to view subduction zones as areas of net crustal growth. Convergent plate margins are divided into those showing long‐term landward retreat of the trench and those dominated by accretion of sediments from the subducting plate. Tectonic erosion is favored in regions where convergence rates exceed 6 ± 0.1 cm yr−1 and where the sedimentary cover is <1 km. Accretion preferentially occurs in regions of slow convergence (<7.6 cm yr−1) and/or trench sediment thicknesses >1 km. Large volumes of continental crust are subducted at both erosive and accretionary margins. Average magmatic productivity of arcs must exceed 90 km3 m.y.−1 if the volume of the continental crust is to be maintained. Convergence rate rather than height of the melting column under the arc appears to be the primary control on long‐term melt production. Oceanic arcs will not be stable if crustal thicknesses exceed 36 km or trench retreat rates are >6 km m.y.−1. Continental arcs undergoing erosion are major sinks of continental crust. This loss requires that oceanic arcs be accreted to the continental margins if the net volume of crust is to be maintained.
Toward creating isotropic microwave composites with negative refraction
Authors: Simovski C. R. , Sauviac B.
Published: April 2004

The properties of artificial isotropic microwave composites which would possess simultaneously negative permittivity and permeability are studied theoretically. Four kinds of composites are considered. Two of them concern media with split‐ring resonator particles with different particle arrangements. The other two are realized with Omega particles. An analytical antenna model of the electromagnetic behavior of a split‐ring resonator (SRR) is suggested and verified by numerical simulations. Next, material parameters of composite media made with SRR or Omega particles are calculated. Both mixtures can create negative index media, but Omega composites are more prospective for obtaining negative real values of permittivity and permeability than the split‐ring resonators.
The deep structure of the Larderello‐Travale geothermal field from 3D microearthquake traveltime tomography
Authors: Vanorio T. , De Matteis R. , Zollo A. , Batini F. , Fiordelisi A. , Ciulli B.
Published: April 2004

With the aim of exploring the deep structure of the Larderello‐Travale (LT) geothermal field, a high resolution 3‐D tomographic inversion of microearthquake traveltimes has been performed. Results show that the deep part of the Larderello‐Travale field is characterized by the presence of a structure having a velocity range of 6.0–6.5 km/s and a convex shape deepening towards the northeastern and the southeastern sides of the field. Earthquakes are mostly concentrated on the top of the high velocity structure and below the ‘K horizon’ implying a transition of rheological properties at depth. The reported dependence on time of ts‐tp observed at one station located above an earthquake cluster suggests that the variation in pore fluid pressure might be responsible for the transition of rheological properties along the contact. In such an area, changes in pore fluid pressure might be related to time‐dependent hydraulic mechanisms that are very effective in crustal rocks at elevated temperatures.
Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise
Authors: Shapiro N. M. , Campillo M.
Published: April 2004

We demonstrate that the coherent information about the Earth structure can be extracted from the ambient seismic noise. We compute cross‐correlations of vertical component records of several days of seismic noise at different pairs of stations separated by distances from about one hundred to more than two thousand kilometers. Coherent broadband dispersive wavetrains clearly emerge with group velocities similar to those predicted from the global Rayleigh‐wave tomographic maps that have been constrained using ballistic surface waves. Those results show that coherent Rayleigh waves can be extracted from the ambient seismic noise and that their dispersion characteristics can be measured in a broad range of periods. This provides a source for new types of surface‐wave measurements that can be obtained for numerous paths that could not be sampled with the ballistic waves and, therefore, can significantly improve the resolution of seismic images.
Assessment of genetic relationships among Cucumis spp. by SSR and RAPD marker analysis
Authors: ZHUANG F. Y. , CHEN J. F. , STAUB J. E. , QIAN C. T.
Published: April 2004

The first successful production of a sterile interspecific hybrid obtained from a cross between Cucumis hystrix Chakr. (2n = 2x = 24) and Cucumis sativus var. sativus L. (2n =2x = 14), and its subsequent fertility restoration through chromosome doubling provide an effective means for investigating genetic relationships among Cucumis spp. In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were used to investigate relationships among C. s. var. sativus L., C. s. var. hardwickii (R.) Alef., C hystrix, C. hytivus Chen & Kirkbride (the amphidiploid species from chromosome doubling of the C. sativus x C. hystrix interspecific hybrid, 2n = 38), C. melo (2n =2x = 24) and C. metuliferus Meyer and Naudin (2n =2x= 24). A total of 109 SSR bands and 398 RAPD primed sites were used to calculate Jaccard's distance coefficients for cluster analysis using a unweighted pair‐group method using an arithmetic averaging (UPGMA) algorithm. The genetic relationships identified using SSR and RAPDmarkers were highly concordant, such that the correlation between SSR and RAPDgenetic distance (GD) estimates was r = 0.94. SSR and RAPDanalysis of 22 accessions allowed for their grouping into two distinct groups designated as CS and CM. While group CS consisted of 11 C. sativus genotypes, and the C. hytivus and C. hystrix accessions, group CM included six C. melo genotypes and C. metuliferus. The GD values between C. hystrix and C. sativus ascribed by SSR and RAPD matrices were 0.59 and 0.57, respectively. These GDs were smaller than those detected between C. hystrix and C melo (0.87 and 0.70 derived from SSR and RAPD markers, respectively).
Coupled oscillations of flow along a perforated plate
Authors: Celik E. , Rockwell D.
Published: April 2004

Turbulent shear flow past a perforated plate bounded by a closed cavity can give rise to highly coherent oscillations, which have a wavelength of the order of the plate length. The present investigation focuses on the coupling between unsteady events on either side of the plate when the oscillations are self-sustaining. A cinema technique of high-image-density particle image velocimetry, which provides a space-time representation of the unsteadiness at a large number of locations over entire planes, is employed to characterize the distinctively different patterns of flow structure on the back (low-speed) side of the plate relative to those on the front (high-speed) side. Global cross-spectral analysis leads to patterns of spectral peaks and phase variations, along and across the plate. This approach, along with complementary types of image evaluation, delineates the physics of the oscillations, which include downstream propagating disturbances along either side of the plate and a coherent region of unsteadiness at its trailing-edge. On the backside of the plate, a sequence of upstream-oriented, pulsatile jets are formed, and the time-averaged flow pattern is a counterflow wall jet.
A numerical investigation of wall effects up to high blockage ratios on two-dimensional flow past a confined circular cylinder
Authors: Sahin Mehmet , Owens Robert G.
Published: April 2004

A finite volume method based on a velocity-only formulation is used to solve the flow field around a confined circular cylinder in a channel in order to investigate lateral wall proximity effects on stability, Strouhal number, hydrodynamic forces and wake structure behind the cylinder for a wide range of blockage ratios (0.1<β⩽0.9) and Reynolds numbers (0<Re⩽280). For blockage ratios less than approximately 0.85 a first critical Reynolds number is identified at which a supercritical Hopf bifurcation of the symmetric solution occurs. For blockage ratios greater than about 0.687 and at Reynolds numbers exceeding the first critical Reynolds number a second curve of neutral stability is seen, representing a pitchfork bifurcation of the steady symmetric solution to one of two possible steady asymmetric solutions. Either side of the neutral stability curve for the pitchfork bifurcation our linear stability analysis and direct numerical simulations demonstrate that although the flow is linearly stable it is unstable to finite two-dimensional perturbations. At blockage ratios larger than about 0.82 the steady asymmetric solutions also become unstable through a Hopf bifurcation. In contrast with the first Hopf bifurcation of the symmetric solution at lower Reynolds numbers numerical calculations of the lift coefficient reveal that the oscillations are no longer symmetric in the rising and falling parts of each cycle. Very strong vortices shed from the cylinder and the wall cause drastic increases in the amplitudes of the lift and drag coefficients. A co-dimension 2 point where pitchfork and Hopf bifurcations occur simultaneously has been located in parameter space. Altogether, four distinct regions in the parameter space (β,Re)∈(0,0.9]×(0,280] have been identified, each corresponding to a different class of flow: (i) Steady symmetric flow, (ii) symmetric vortex shedding, (iii) steady asymmetric flow, and (iv) asymmetric vortex shedding, where a periodic-in-time flow is classed as symmetric or asymmetric depending on whether the time-average over one cycle of the lift coefficient is zero or not. Numerical solutions are computed on meshes having up to 1.8 million degrees of freedom. Extensive comparisons are made with the results available in the literature.
The relaxation of two-dimensional rolls in Rayleigh–Bénard convection
Authors: Paul M. R. , Catton I.
Published: April 2004

Large aspect ratio, two-dimensional, periodic convection layers containing a Boussinesq fluid of finite Prandtl number bounded by rigid or free horizontal surfaces are investigated numerically. The fluid equations are solved using both a standard pseudospectral and a Fourier integral method for the time evolution of finite initial perturbations, both random thermal perturbations and localized roll disturbances, into a final equilibrium state. The suggestion that a Fourier integral solution method is required to yield roll relaxation, the two-dimensional process increasing the convection wavelength to values larger than critical, is investigated. Roll relaxation is found for both free-slip and no-slip surfaces using either solution method as long as the initial state is chosen to be of the form of a localized roll disturbance. A wide variety of simulations are performed and roll relaxation is found to be independent of the periodic domain length, weakly dependent on the Rayleigh number and dependent upon the magnitude of the initial localized roll disturbances.
Four dynamical regimes for a starting plume model
Authors: Hier Majumder Catherine A. , Yuen David A. , Vincent Alain P.
Published: April 2004

The growth of two-dimensional plumes was modeled numerically to study the dynamics of plumes with Rayleigh numbers in the range of 104 to 108 and Prandtl numbers in the range of 0.025 to 10 000. In this study we deal with a geometry driven by a heated line source, which is different from the basally heated Rayleigh–Bénard convection between two horizontal plates. We found four different regimes for plume growth: a diffusive-viscous regime characterized by both thick thermal and velocity boundary layers; an inviscid-diffusive regime with thin velocity and thick temperature boundary layers; a viscous nondiffusive regime with thick velocity boundary layers and thin thermal ones; and an inviscid nondiffusive regime with both thin velocity and narrow thermal boundary layers. We also studied the dependence of the Nusselt number on height for various Rayleigh and Prandtl numbers. We found that plumes with Prandtl numbers as high as 104 grown at a high Rayleigh number (108) are significantly different from plumes developed in an infinite Prandtl number fluid.
Streamwise scaling of streaks in laminar boundary layers subjected to free-stream turbulence
Authors: Lundell Fredrik , Alfredsson P. Henrik
Published: April 2004

A flat plate laminar boundary layer subjected to free-stream turbulence, generated by grids upstream of the leading edge, has been studied. Correlations between a wall wire and a hot wire in the boundary layer have been obtained. The hot wire has been traversed to 328 positions for each of the five wall-wire positions studied. The length, height, and width of the correlation distributions is seen to increase in the downstream direction being self-similar in coordinates scaled with the boundary-layer length scale. The propagation speeds of the structures are obtained from the data and its variation in the streamwise and wall-normal directions is found to agree with what is obtained from a simple kinematic model.
Short-wave cooperative instabilities in representative aircraft vortices
Authors: Fabre David , Jacquin Laurent
Published: April 2004

This paper considers the short-wave cooperative instabilities in a family of vortices representative of aircraft wakes. These vortices are characterized by two core scales, an internal core scale a1 and an external core scale a2, and their azimuthal velocity follows a power law V(r)∼r−α in the intermediate zone (a1<r<a2). The results are compared to the cases of the Rankine (constant) and Lamb–Oseen (Gaussian) vortices, and to the elliptic instability theory. The unstable wavelengths and the structure of the unstable modes are characterized as functions of the base flow parameters α and a2/a1. For 0.5⩽α⩽1, the wavelength of the instability is of the order of the internal scale a1 and the unstable modes only affect the internal core. In this case the growth rate of the instability is in accordance with the predictions of the elliptical instability theory and is a growing function of the parameter a2/a1. For 0⩽α<0.4, the wavelength of the instability is of the order of the external scale a2 and the unstable modes extend into the intermediate zone. In this case the growth rate of the instability differs from the predictions of the elliptical instability theory and is independent upon the parameter a2/a1. Interestingly, a sharp transition between these two regimes occurs for 0.4<α<0.5, in a range of parameters corresponding to experimentally measured trailing wakes. In this range, the bands of wave numbers affected by the instability are particularly large and may coalesce into a broadband spectrum.
Evolution scales for wave regimes in liquid film flow over a spinning disk
Authors: Matar Omar K. , Sisoev Grigori M. , Lawrence Chris J.
Published: April 2004

We study the spatiotemporal development of a thin viscous film flowing over a spinning disk. A coupled system of evolution equations for the film thickness and volumetric flow rates in the radial and azimuthal directions is derived using the Karman–Polhausen method, assuming a parabolic profile for the film velocity. In the limit of large Eckman number, this system reduces to equations previously used to study the falling film problem. Numerical solutions of the system are obtained starting from initially waveless profiles, which correspond to the Nusselt solution for the case of a spinning disk. Results from these simulations reveal the development of finite-amplitude waves, which, locally, approximate closely to the shape of quasisteady periodic traveling waves. These waves are found to be in good agreement with the predictions of the localized version of the model.
Polymer chain dynamics in Newtonian and viscoelastic turbulent channel flows
Authors: Gupta V. K. , Sureshkumar R. , Khomami B.
Published: April 2004

Polymer chain dynamics in Newtonian and viscoelastic turbulent channel flows are examined by Brownian dynamics simulations utilizing FENE and FENE–P [finitely extensible nonlinear elastic(–Peterlin)] dumbbell models. The chain extension is predicted by using an algorithm that combines the two-step semi-implicit predictor–corrector scheme for the evaluation of dumbbell trajectories with the direct numerical simulation of turbulent flow field. The influence of maximum extensibility of the polymer chain, b, the friction Reynolds number, Reτ, and friction Weissenberg number, Weτ, on the chain dynamics in the viscous sublayer, buffer layer, and turbulent core is examined. For a given value of b, the average chain extension, 〈|Q|〉, approaches an asymptotic value with increasing Weτ. For given values of Weτ and the friction Reynolds number, Reτ, 〈|Q|〉/b decreases although 〈|Q|〉 itself increases with increasing b. Significant qualitative and quantitative differences exist between the predictions obtained using the FENE and FENE–P models. Specifically, 〈|Q|〉 values predicted by the FENE–P model are greater than those predicted by the FENE model for given Weτ and b. The normalized probability distribution function (pdf) for 〈|Q|〉 predicted by the two models also shows differences. Violated states, i.e., configurations with |Q|>b, are seen for the FENE–P model while such states are not seen for the case of FENE model. Despite these differences, the quantitative differences between the predictions of the two models for 〈QQ〉 in the viscous sublayer and the buffer layer can be practically eliminated by suitable renormalization of the maximum extensibility parameter. This renormalization also reduces the disparity between the FENE and FENE–P model predictions for the shear stress and transient extensional viscosity. Since mean chain extension and transient extensional behavior play a significant role in drag reduction (DR) such renormalization procedures could be used to improve the accuracy of continuum-level model predictions of DR. Comparison of simulation results obtained for Reτ=125 and 180 shows that the dependence of pdf for 〈|Q|〉 on Weτ and the renormalization proposed are not strongly influenced by Reτ. However, the fraction of highly extended states is larger for Reτ=180 while the states with low to moderate extension are smaller. Consequently 〈QQ〉 increases only marginally with increasing Reτ.
On Boussinesq models of constant depth
Authors: Zhang Jin E. , Chen Chunli , Li Yishen
Published: April 2004

The mathematical properties, such as integrability, symmetries and multiple solitary wave solutions of Boussinesq models of constant depth are studied. An integrable modified Boussinesq model has been identified.
Three-dimensional numerical simulations of the transition of flow past a cube
Authors: Saha A. K.
Published: April 2004

The wake of a cube placed in a uniform flow is numerically studied. The present study concentrates on the first two transitions, one spatial and the other a temporal one. Computations are carried out for a Reynolds number range of 20–300. Starting from a steady symmetric flow, the transition to asymmetric steady flow occurs at a Reynolds number between 216 and 218. The loss of symmetry increases with increasing Reynolds number. The asymmetric steady flow experiences a Hopf bifurcation at a Reynolds number between 265 and 270 and becomes unsteady but maintains the planar symmetry. The transitions of the present study are compared to the transitions of flow past a square cylinder and a sphere. The transition sequence and flow structures match closely to that of a sphere. The drag and side force coefficients are calculated and it is observed that they are in accordance with the spatial structures of the wake. The drag coefficient is found to decrease with Reynolds number in the steady flow regime. Similarly, one component of the side force coefficients increases while the other component remains zero with increasing Reynolds number for the asymmetric flow.