bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study of prenatal ultrasound findings and post‐mortem examination in a tertiary referral centre
Authors: Johns Nina , Al‐Salti Wasim , Cox Phillip , Kilby Mark D.
Published: May 2004

This retrospective study compares the findings of prenatal ultrasound, performed in a tertiary fetal medicine centre, with the results of post‐mortem examination in pregnancies complicated by suspected fetal abnormality that results in fetal loss. The study was carried out over a year at a teaching hospital, Fetal Medicine Centre and Regional Centre for Perinatal Pathology.

Results were directly compared and the level of agreement between the ultrasound and post‐mortem findings described. These were classified as having complete agreement; major agreement or major disagreement. The group of cases with major agreement between findings was further divided into those with significant, or minor, additional findings at post‐mortem examination.

Over the 12‐month period, 153 ultrasound cases were identified, of which 47 were also examined by autopsy and were thus suitable for comparison in this study (30.7%). Complete agreement between ultrasound and post‐mortem findings was found in 22 cases (46.8%). In 24 cases (51.1%), major agreement between ultrasound and post‐mortem findings was seen. Of these, 11 had minor additional findings at post‐mortem examination and 13 were found to have significant additional findings at post‐mortem (27.7%), adding to the eventual diagnosis. In 12.8% of cases, post‐mortem examination provided a definitive diagnosis. Only in one case was there complete discordance in the findings of the ultrasound examination and the autopsy (2.1%).

No major disagreement between ultrasound and post‐mortem findings was seen in 98% of cases.

This study confirms the accuracy of prenatal ultrasound diagnosis in specialist centres, whilst emphasising the continuing importance of post‐mortem examination in cases of fetal malformation to refine and, in some cases, define the diagnosis. Copyright © 2004 John Wiley & Sons, Ltd.
Semiquantitative assessment of myelination using magnetic resonance imaging in normal fetal brains
Authors: Abe Seiji , Takagi Kenjiro , Yamamoto Tatsuo , Okuhata Yoshitaka , Kato Toshinori
Published: May 2004

Objectives

To evaluate the development of myelination in normal fetuses quantitatively using magnetic resonance (MR) imaging in relation to gestational age (GA).

Methods

Fetal MR images were obtained from 101 fetuses between 26 and 39 weeks of gestation with no neurological problems. Regions of interest were designated in frontal lobe, corona radiata, optic radiation, thalamus, pons, cerebellar vermis, and vitreous body. The signal intensity ratio (SIR) was calculated by the signal intensity of each of these designated areas to that of the vitreous body and analyzed in relation to GA.

Results

The SIR of the frontal lobe did not vary significantly with GA. The SIR of the corona radiata and the optic radiation decreased significantly with GA (P < 0.05); after 34 weeks of gestation, they decreased sharply. The SIR of the thalamus, the pons, and the cerebellar vermis was significantly smaller than that of the cerebral white matter at 26 weeks of gestation (P < 0.05) and decreased significantly with GA (P < 0.05).

Conclusion

Changes in the SIR approximately corresponded to the time‐course of progression of myelination in the previous histopathological reports. Semiquantitative evaluation on MR images may allow prenatal diagnosis of a delay or deficit of myelination. Copyright © 2004 John Wiley & Sons, Ltd.
Identification of two mutations for ataxia telangiectasia among the Druze community
Authors: Fares Fuad , Axelord Ran Sivan , David Miriam , Zelnik Nathanel , Hecht Yehudah , Khairaldeen Hasan , Lerner Aaron
Published: May 2004

Ataxia telangiectasia (AT) is a rare autosomal recessive disease characterized by progressive cerebellar ataxia, immunodeficiency, susceptibility to lymphoreticular malignancies and cancer predisposition, hypersensitivity to ionic radiation and chromosomal instability. In this study, we report a founder effect of AT with two different mutations: 1339 C > T and 6672 del GG together with 6677 del TACG, found in four Israeli Druze clans originating from three different Druze centers in the Middle East (Lebanon, Syria and Jordan). The 1339 C > T mutation, which results in a stop codon at position 447 of the ATM protein, was observed in two unrelated clans originating from Lebanon and Jordan. The 6672 del GG/6677 del TACG mutation was observed in two unrelated clans originating from Syria and Lebanon. In the present study, simple and fast detection assays were developed for both mutations. The ability to identify AT carriers routinely provides a unique opportunity for prenatal diagnosis, genetic counseling as well as marriage guidance in the Druze community. Copyright © 2004 John Wiley & Sons, Ltd.
Prenatal diagnosis of autosomal dominant hereditary spastic paraplegia (SPG4) using direct mutation detection
Authors: Nielsen Jørgen E. , Koefoed Pernille , Kjaergaard Susanne , Jensen Lisa Neerup , Nørremølle Anne , Hasholt Lis
Published: May 2004

Objective

To present a report on prenatal diagnosis using direct SPG4 gene analysis in a family with autosomal dominant hereditary spastic paraplegia (AD‐HSP).

Methods

Genetic linkage and haplotype analysis were previously carried out with chromosome 2p markers. DNA was obtained from affected individuals, the affected father, the mother, and fetal DNA from an ongoing pregnancy by chorionic villus sampling (CVS) in the first trimester. The spastin gene (SPG4) was completely sequenced.

Results

A novel 832insGdelAA frameshift mutation, predicted to cause loss of functional protein, was identified in the affected father and in the fetal DNA.

Conclusions

This is the first report on direct prenatal diagnosis of chromosome 2p–linked AD‐HSP (SPG4). In addition, we report a novel SPG4‐combined small insertion/deletion mutation in exon 5, which may be the first SPG4 mutational hot spot. Copyright © 2004 John Wiley & Sons, Ltd.
Prenatal diagnosis of an isochromosome 5p in a fetus with increased nuchal translucency thickness and pulmonary atresia with hypoplastic right heart at 14 weeks
Authors: Paulick J. , Tennstedt C. , Schwabe M. , Körner H. , Bommer C. , Chaoui R.
Published: May 2004

We report on a fetus presenting with increased nuchal translucency at 11 weeks' gestation, suggesting cystic hygroma. Chorion villous sampling was performed, and cytogenetic analysis revealed a supernumerary isochromosome 5p leading to tetrasomy 5p: 47,XX,+ i(5p)[7]/46,XX[5] after short‐term culture and 47,XX,+ i(5p)[20] after long‐term culture. Subsequent targeted sonographic follow‐up at 12 and 14 weeks revealed further increase of the NT to 6.4 mm and the additional presence of a congenital heart defect (pulmonary atresia with intact ventricular septum). Termination of pregnancy was performed, and the heart defect was confirmed. Isochromosome 5p was found in varying proportions in all examined organs. Only a few cases of mosaic tetrasomy 5p have been reported in the literature, and recent reports on prenatally detected isochromosome 5p showed a possible relationship to increased nuchal translucency in some cases and also a possible role of confined mosaicism in others. Whereas cases with confined mosaicism did not show suspicious signs on ultrasound, true mosaicism conversely showed increased nuchal thickness as well as structural abnormalities. This is the first report on the association of a cardiac defect with this chromosome aberration. Copyright © 2004 John Wiley & Sons, Ltd.
A novel PCR approach for prenatal detection of the common NEMO rearrangement in incontinentia pigmenti
Authors: Steffann Julie , Raclin Valérie , Smahi Asmae , Woffendin Hayley , Munnich Arnold , Kenwrick Sue J. , Grebille Anne‐Gaelle , Benachi Alexandra , Dumez Yves , Bonnefont Jean‐Paul , Hadj‐Rabia Smaïl
Published: May 2004

Objectives

Incontinentia pigmenti (IP) is a rare X‐linked dominant genodermatosis that is usually lethal in males in the prenatal period. Largely 80% of cases are accounted for by a large‐scale deletion encompassing exons 4 to 10 of the NEMO gene. The aim of this work was to facilitate prenatal diagnosis of IP by devising a novel test for detection of the prevalent NEMO deletion.

Methods

We devised a sensitive and reproducible multiplex PCR test enabling simultaneous amplification of the deleted and wild‐type NEMO genes in IP female individuals.

Results

Combination of this DNA test, with Xq28 linkage analysis and X‐inactivation pattern study enabled us to offer an IP prenatal diagnosis in 15 of the 16 couples at a 50% risk to have an affected offspring.

Conclusion

A current approach to IP prenatal diagnosis is proposed on the basis of the previously mentioned molecular tools. Copyright © 2004 John Wiley & Sons, Ltd.
Speed‐up of radiation treatment planning using a workstation cluster
Authors: Sato Hiroyuki , Nakagawa Takafumi , Yoda Kiyoshi , Nakajima Katsuto , Sakamoto Hidenobu , Endo Masahiro
Published: May 2004

In treatment planning in a heavy particle cancer radiation facility which is utilized by multiple remote medical institutions, it is necessary to calculate accurately the three‐dimensional dose distribution within the body of the patient in order to achieve efficient treatment. However, this presents a problem, since a long processing time is needed, which degrades the efficiency of treatment planning. In order to handle this problem, the authors used a cluster system in which Alpha 21164A CPUs were connected over a 100 Mbit/s Ethernet to speed up the dose distribution calculation (Dose) and digital reconstructed X‐ray image regeneration (DRR) by parallel processing. Parallel calculation is performed by segmenting the calculation area. The communication time among processors is reduced by data compression, and the load is made uniform by assigning more than one area to a processor. As a result of evaluation experiments, calculations performed iteratively by varying parameters at the actual site of medical care were accelerated by using 10 processors, by a factor of 7 for Dose, and 9 for DRR. In other words, the speed was improved in proportion to the number of processors. This implies that processing which has required several tens of seconds can now be handled in 3 to 6 seconds, which is short enough for the user to wait before the terminal. The objective is to make the system usable by multiple remote medical institutions by refining system functions such as fault recovery in order to ensure its reliability as a calculation server. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(8): 96–106, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10277
A retrieval method of a double array in secondary storage
Authors: Fuketa Masao , Kashiwagi Yuichiro , Kashiji Shinkaku , Morita Kazuhiro , Aoe Jun‐ichi
Published: May 2004

The trie method is widely used as a dictionary retrieval technique in natural language processing, and the double array method is extremely good in terms of high retrieval speed and compactness as a data structure for implementing the trie method. However, although placing the double array in main storage is effective for fast retrieval, the size of the double array increases as the number of storage keys increases. Therefore, in this paper, the authors propose a divided double array method that can execute retrieval efficiently even when using a small main storage area and can also further reduce the amount of storage by dividing the double array and storing it in secondary storage. However, a problem with this technique is that the number of accesses to secondary storage increases because the divided tries must be scanned. To deal with this problem, the authors proposed a technique that reduces the number of times the divided tries are scanned to maintain the fast access speed of the double array. They performed experiments for sets containing from 70,000 to 230,000 keys, and from the results, it was apparent that the number of accesses to secondary storage during retrieval for a single key was less than or equal to 2, and the storage capacity required for the divided tries was reduced by approximately 50% compared with the undivided trie. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(8): 72–81, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10481
Design and implementation of data sharing architecture for multifunctional robot development
Authors: Matsusaka Yosuke , Oku Kentaro , Kobayashi Tetsunori
Published: May 2004

In this paper, we designed and implemented an intermodule connection architecture, which is required for the development of modules for a multifunctional robot. The proposed and implemented architecture is a dual bus architecture characterized by the fact that a composite blackboard and publish/subscribe service for realizing flat relationships among modules and the dynamic switching of information flows by the modules themselves can be compatible with tight integration and a guarantee of scalability. Through an implementation of conversational tasks, which used speech, acoustic, and image information in an integrated manner, it is confirmed that a tightly integrated system can be developed in a short period. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(8): 54–65, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10585
A non‐parametric approach to the design and analysis of two‐dimensional dose‐finding trials
Authors: Ivanova Anastasia , Wang Kai
Published: May 2004

This paper investigates the design and analysis of dose‐finding trials with two agents. The set of doses for each agent is fixed in advance. The goal of the trial is to find the set of dose combinations with probability of toxicity closest to a pre‐specified value. For each of the two agents we assume that the probability of toxicity of an agent is non‐decreasing with dose when the dose of the other agent is fixed. Using this assumption we construct a new non‐parametric design that operates on a two‐dimensional grid of all possible dose combinations. A bivariate isotonic regression estimator of the maximum tolerated combinations is described. We conclude that the new design and the bivariate isotonic estimator are superior to the procedure where several independent dose‐finding trials are run. Copyright © 2004 John Wiley & Sons, Ltd.
SEFT: a search engine for text
Authors: de Kretser Owen , Moffat Alistair
Published: May 2004

We present a software tool called seft which balances the convenience of search tools such as grep with the functionality of full‐text index‐based information retrieval. Based on a novel retrieval heuristic which uses term locality as a guide to relevance, seft combines the freedom of natural language queries with the benefits of a ranked answer list and easy inspection of retrieval results. While not as fast as grep‐style tools, seft provides a valuable facility for impromptu personal information retrieval tasks. Copyright © 2004 John Wiley & Sons, Ltd.
Experimental determination of trace element partitioning between garnet and silica‐rich liquid during anhydrous partial melting of MORB‐like eclogite
Authors: Pertermann M. , Hirschmann M. M. , Hametner K. , Günther D. , Schmidt M. W.
Published: May 2004

We present new experimentally determined trace element partition coefficients for nine garnet/melt and two clinopyroxene/melt pairs at 2.9–3.1 GPa and 1325°–1390°C, applicable to anhydrous partial melting of MORB‐like eclogite in the upper mantle. Phase compositions are similar to those documented in partial melting experiments of eclogite at these conditions: garnets with 16–25% grossular component and 0.4–2.0 wt % TiO2 coexist with siliceous partial melts having 52.4–57.1 wt % SiO2 and 1.1–6.7 wt % TiO2. Observed garnet/melt partitioning depends on TiO2 concentrations in garnet. Among the high‐TiO2 garnets (1.4–2.0 wt % TiO2), partition coefficients (Dgt/melt) increase with increasing grossular content of garnet (16–24%), but for the low‐TiO2 garnets (0.4–0.6 wt % TiO2) there is no difference in partitioning behavior at 19–24% grossular. In general, partition coefficients for the low‐TiO2 garnets tend to be higher than for the high‐TiO2 garnets. DZr and DHf increase with higher grossular content, as does DZr/DHf, but DZr and DHf always remain smaller than unity, and TiO2 in garnet appears to have little effect on DZr/DHf. DTh and DU have average values of 0.0012 and 0.0111 for the high‐TiO2 garnets and 0.0074 and 0.0376 for the low‐TiO2 garnets (DU/DTh of 9.1 and 5.1, respectively), affirming that partial melting of eclogite in the upper mantle can produce liquids with significant (230Th)/(238U) excess. D values of highly charged cations (Nb, Ta, Th, U) are lower in high‐TiO2 garnets. This is likely because Ti4+ occupying the garnet Y site requires charge balance by 2+ cations in Y or 3+ cations in Z, thereby limiting the availability of these charge‐balancing substitutions to accommodate other highly charged cations. The overall range of our new garnet/melt partition coefficients, regardless of Ti and grossular content, is similar to literature garnet/melt partitioning data applicable to garnet peridotite melting, and therefore bulk partition coefficients for eclogite and peridotite depend largely on mineral modes and choice of partitioning data for clinopyroxene. Using our new data and previously published data from the literature, we calculate bulk partition coefficients appropriate for two MORB‐like eclogites (82% clinopyroxene + 18% garnet and 75% clinopyroxene + 25% garnet) and a garnet peridotite (60% olivine + 17% orthopyroxene + 13% clinopyroxene + 10% garnet). Bulk partition coefficients are generally much higher for MORB‐like eclogite when compared to garnet peridotite, with the exception of Th and U. However, the ratios of bulk partition coefficients of eclogite and garnet peridotite are similar for pairs such as DSm/DYb, DZr/DHf and DU/DTh, indicating that both lithologies can induce similar trace element fractionations during partial melting in the presence of garnet.
Climate variability in the Botswana Kalahari from the late Pleistocene to the present day
Authors: Kulongoski Justin T. , Hilton David R. , Selaolo Edson T.
Published: May 2004

Noble gas concentrations and oxygen isotopes in groundwaters from the Kalahari Desert in Botswana contain a ∼45 ka paleotemperature record indicating that mean annual temperatures during the period from 24 ka BP to 45 ka BP were 5.2 ± 1.5°C cooler than from ∼16 ka to the present day. In addition to enrichments in oxygen‐18, groundwaters recharged after 16 ka BP also contain higher concentrations of excess‐air (entrained air bubbles). Taken together, the noble gas, oxygen isotope, and excess‐air based paleoclimate archives provide evidence that the high interior desert of southern Africa was both cooler and dryer prior to the Last Glacial Maximum (LGM). Cool, dry conditions also suggest a weaker hydrological cycle in southern Africa. This is contrary to the predicted enhancement of monsoon strength by increased summer insolation in the southern tropics induced by orbital precession during the LGM.
Recalculated probability ofM≥ 7 earthquakes beneath the Sea of Marmara, Turkey
Authors: Parsons Tom
Published: May 2004

New earthquake probability calculations are made for the Sea of Marmara region and the city of Istanbul, providing a revised forecast and an evaluation of time‐dependent interaction techniques. Calculations incorporate newly obtained bathymetric images of the North Anatolian fault beneath the Sea of Marmara [Le Pichon et al., 2001;Armijo et al., 2002]. Newly interpreted fault segmentation enables an improved regional A.D. 1500–2000 earthquake catalog and interevent model, which form the basis for time‐dependent probability estimates. Calculations presented here also employ detailed models of coseismic and postseismic slip associated with the 17 August 1999M= 7.4 Izmit earthquake to investigate effects of stress transfer on seismic hazard. Probability changes caused by the 1999 shock depend on Marmara Sea fault‐stressing rates, which are calculated with a new finite element model. The combined 2004–2034 regional Poisson probability ofM≥ 7 earthquakes is ∼38%, the regional time‐dependent probability is 44 ± 18%, and incorporation of stress transfer raises it to 53 ± 18%. The most important effect of adding time dependence and stress transfer to the calculations is an increase in the 30 year probability of aM≥ 7 earthquake affecting Istanbul. The 30 year Poisson probability at Istanbul is 21%, and the addition of time dependence and stress transfer raises it to 41 ± 14%. The ranges given on probability values are sensitivities of the calculations to input parameters determined by Monte Carlo analysis; 1000 calculations are made using parameters drawn at random from distributions. Sensitivities are large relative to mean probability values and enhancements caused by stress transfer, reflecting a poor understanding of large‐earthquake aperiodicity.
Ice ablation as evidence of climate change in the Alps over the 20th century
Authors: Vincent C. , Kappenberger G. , Valla F. , Bauder A. , Funk M. , Le Meur E.
Published: May 2004

Over fifty years of cumulative annual mass balance data for several glaciers in the Alps shows similar fluctuations which seem to provide evidence of a common climatic signal. Separate winter and summer mass balance measurements from the Claridenfirn (glacier in Switzerland) since 1914 and the Sarennes glacier (France) since 1949 show that (1) the annual mass balance is primarily driven by the summer mass balance term and (2) melting rate variations with time are very similar for these two glaciers located 290 km apart. The increase in the ablation rate of 0.5 cm w.e. day−1 between the two periods 1954–1981 and 1982–2002 over these two glaciers corresponds to a 20 Wm−2 rise in the energy flux at the glacier surface. These results suggest that a common summer melting rate change may have affected the Alps as a whole. Detailed observations on the Sarennes glacier show that the origin of this strong increase in summer ablation since 1982 is not only a rise in the summer melting rate, but also an increase in the ablation period during the months of September and October.
Measurements of Mexico City nanoparticle size distributions: Observations of new particle formation and growth
Authors: Dunn Matthew J. , Jiménez José‐Luis , Baumgardner Darrel , Castro Telma , McMurry Peter H. , Smith James N.
Published: May 2004

Continuous measurements of the size distribution of atmospheric aerosol in the 3–48 nm diameter range were performed in the Mexico City metropolitan area. These measurements were made during the period 10–20 April 2003 at a ground‐based, mountain pass site in the southeast corner of the Mexico City Federal District and during the period 2–11 May 2003 at the CENICA site located near the city center. The objectives of this work were to determine the frequency of new particle formation and to characterize the atmospheric chemical and meteorological conditions that lead to these events. Several new particle formation events were recorded during the study. Events observed in the mountain pass correlate with northerly winds and elevated levels of sulfur dioxide in the mid‐morning while events observed in the city correlate with elevated concentrations of sulfur dioxide and low particulate matter mass concentrations in the afternoon hours.
Dynamic mechanisms of the gulf surge
Authors: Zehnder Joseph A.
Published: May 2004

The gulf surge is a summertime phenomenon associated with the North American Monsoon that transports moisture from the Gulf of California into western portions of the United States. This phenomenon has been acknowledged operationally and by researchers for over 30 years. The surge is typically linked to the presence of some sort of low‐pressure system such as an easterly wave, mesoscale convective system, or hurricane located near the southern end of the Gulf of California. Proposed mechanisms for the gulf surge are gravity currents, ageostrophic flows, Kelvin, or Rossby edge waves. The purpose of this paper is to describe the fundamental dynamics of each of these mechanisms and assess their plausibility through scale analyses and idealized numerical simulations and to suggest signatures that may appear in data and output of more sophisticated numerical models.
Nonadiabatic transition in the dissociation process from inner valence states of O2+
Authors: Hirayama Ryo , Yamamoto Norifumi , Miyoshi Eisaku
Published: May 2004

In a previous paper [J. Chem. Phys. 119, 7693 (2003)] we reported a study of the electronic structures of inner valence states of O2+ and the dissociation process, where there remained some questions as to the origins of the dissociation fragment formation of the O+(2D)+O(3P) limit in observed spectra. In this paper, we present the results of calculations of the nonadiabatic transition probabilities of the multichannel dissociation process from the inner valence states of O2+ and reproduce the general features of observed spectra previously reported, including fragment formation, using the Zhu–Nakamura theory.
Realization of nanoscale resolution with a micromachined thermally actuated testing stage
Authors: Lu Shaoning , Dikin Dmitriy A. , Zhang Sulin , Fisher Frank T. , Lee Junghoon , Ruoff Rodney S.
Published: May 2004

The design, fabrication, and characterization of a microelectromechanical systems (MEMS) stress–strain device for testing the mechanical properties of nanomaterials is presented. Thermal actuation, with integrated motion amplification structures, was used to both minimize the operating temperature of the device as well as realize fine motion control over large displacements. The device has a working range from tens of nanometers up to 10 micrometers. Displacements as small as 30 nm per 10 mA input dc current increments were obtained for the first time with thermal actuators micromachined by deep reactive ion etching (DRIE). The height difference (offset) between the moving and fixed platforms was less than 40 nm over the entire working range of the device for the input power range studied. A 0.27 μN force is predicted for an actuator displacement of 30 nm based on mechanical models of the device; the calculated force increases linearly up to 88 μN for the maximum 9.7 μm displacement. The operating characteristics obtained for this initial design suggest that this methodology will be useful in producing a variety of MEMS stress–strain stages custom designed to yield the force and displacement resolution necessary to test many nanomaterials and nanostructures.
Development and trial measurement of synchrotron-radiation-light-illuminated scanning tunneling microscope
Authors: Matsushima Takeshi , Okuda Taichi , Eguchi Toyoaki , Ono Masanori , Harasawa Ayumi , Wakita Takanori , Kataoka Akira , Hamada Masayuki , Kamoshida Atsushi , Hasegawa Yukio , Kinoshita Toyohiko
Published: May 2004

Scanning tunneling microscope (STM) study is performed under synchrotron-radiation-light illumination. The equipment is designed so as to achieve atomic resolution even under rather noisy conditions in the synchrotron radiation facility. By measuring photoexcited electron current by the STM tip together with the conventional STM tunneling current, Si 2p soft-x-ray absorption spectra are successfully obtained from a small area of Si(111) surface. The results are a first step toward realizing a new element-specific microscope.
Two-particle diffusion and locality assumption
Authors: Nicolleau F. , Yu G.
Published: May 2004

A three-dimensional kinematic simulation (KS) model is used to study one- and two-particle diffusion in turbulent flows. The energy spectrum E(k) takes a power law form E(k)∼k−p. The value of this power p is varied from 1.2 to 3, so that its effects on the diffusion of one and two particles can be studied. The two-particle diffusion behaves differently depending on whether the two-particle separation is larger or smaller than the smallest scale of turbulence (Kolmogorov length scale η). When the two-particle mean square separation 〈Δ2(t)〉 is smaller than η2 it experiences a time exponential growth 〈Δ2(t)〉=Δ02eγ(t/tη) but for a very short time. For longer times, when η2<〈Δ2(t)〉<L2, the locality assumption is revisited in terms of two-particle mean diffusivity d/dt〈Δ2(t)〉. In this inertial range we observe that d/dt〈Δ2(t)〉={a ln(〈Δ(t)2〉1/2/η)+b}u′L(η/L)(p+1)/2(〈Δ(t)2〉1/2/η)(p+1)/2 for p⩽3. For Δ0/η≫1 a=0, but a≠0 for Δ0/η⩽1 and as a consequence the pair diffusion cannot have lost its dependence on the initial separation during the exponential growth, i.e., γ is a function of Δ0/η. Our modified Richardson law is compared with two other proposed modifications to Richardson’s power law, namely the virtual time [G. K. Batchelor, Proc. Cambridge Philos. Soc. 48, 345 (1952)] and the correction factor [F. Nicolleau and J. C. Vassilicos, Phys. Rev. Lett. 90, 245003 (2003)]. Further investigations on two-particle diffusion when p=3 give an excellent agreement with the experimental results in P. Morel and M. Larchevêque, J. Atmos. Sci. 31 (1974) for atmospheric turbulent flows. Finally, using two different combined power law energy spectra in KS, the isotropic small scales are found to have no significant role when their largest scale lT is less than 10 times the Kolmogorov length scale η.
Transient growth and instability in rotating boundary layers
Authors: Yecko Philip , Rossi Maurice
Published: May 2004

The three-dimensional temporal instability of rotating boundary layer flows is investigated by computing classical normal modes as well as by evaluating the transient growth of optimal disturbances. The flows examined are the rotating Blasius (RB) and the rotating asymptotic suction layers (RAS), with the rotation axis normal to the basic flow plane. In agreement with an inviscid criterion, streamwise unstable modes are found in both flow cases for anticyclonic rotation: at high Reynolds numbers, one obtains the Rossby number unstable range 0<1/Ro<0.57 for RB, or 0<1/Ro<1 for RAS. Critical Reynolds and Rossby numbers are also determined in both instances. Moreover, the dependence of transient growth with respect to wavenumbers, Rossby and Reynolds numbers is presented for both cyclonic and anticyclonic régimes. In particular, the peak transient growth is computed for a wide range of parameter values within the cyclonic regime and is shown to be reduced by rotation. A scaling analysis with respect to the Reynolds number is performed showing that the standard Re2 scaling is recovered only at very weak rotation. Optimal disturbances resemble oblique vortices. At weak rotation, they are almost streamwise vortices though their structure departs from the classical nonrotating case. Strong rotation imposes two-dimensionality and the optimal disturbances vary weakly in the spanwise direction and exhibit growth by the Orr mechanism.
Computing time scales from reaction coordinates by milestoning
Authors: Faradjian Anton K. , Elber Ron
Published: May 2004

An algorithm is presented to compute time scales of complex processes following predetermined milestones along a reaction coordinate. A non-Markovian hopping mechanism is assumed and constructed from underlying microscopic dynamics. General analytical analysis, a pedagogical example, and numerical solutions of the non-Markovian model are presented. No assumption is made in the theoretical derivation on the type of microscopic dynamics along the reaction coordinate. However, the detailed calculations are for Brownian dynamics in which the velocities are uncorrelated in time (but spatial memory remains).
Combined perturbative-variational investigation of the vibrations of CHBr3 and CDBr3
Authors: Ramesh Sai G. , Sibert Edwin L.
Published: May 2004

A full dimensional vibrational treatment of CHBr3 and CDBr3 using Van Vleck perturbation theory followed by a variational calculation is presented. The calculation of a force field, and its adjustment for better match with experiment, is discussed. The computed eigenstates and spectral features are compared to experiment. Changes in intensities of the ν1 and 2ν4 bands upon simple alterations of the dipole moment expansion are described.
Experimental analysis and visualization of spatiotemporal patterns in spouted fluidized beds
Authors: Palacios Antonio , Finney Charles , Cizmas Paul , Daw Stuart , O’Brien Thomas
Published: May 2004

A numerical characterization based on experimental data of the spouting regime in a two-dimensional fluidized bed is presented. The aspect ratio of the bed allowed for good visualization of the spouting and solids circulation as the spouting jet gas velocity was varied to highlight the visited bifurcation sequence. Digital video sequences were recorded and then preprocessed for numerical analysis. In this paper, the proper orthogonal decomposition (POD) was applied to these data sets in order to identify and separate the dominant spatial features from the temporal evolution of the spouting dynamics. The results indicate that the overall spatiotemporal dynamics can be captured by a few POD eigenfunctions, and that the POD amplitudes can be used to distinguish between varying degrees of spouting.
Magnetoresistive study of the antiferromagnetic–weak ferromagnetic transition in single-crystal La2CuO4+δ
Authors: Belevtsev B. I. , Dalakova N. V. , Savitsky V. N. , Panfilov A. S. , Braude I. S. , Bondarenko A. V.
Published: May 2004

Resistive measurements were made to study the magnetic field-induced antiferromagnetic (AF)—weak ferromagnetic (WF) transition in the La2CuO4 single crystal. The magnetic field (dc or pulsed) was applied normally to the CuO2 layers. The transition manifested itself in a drastic decrease of the resistance in critical fields of 5–7 T. The study is the first to display the effect of the AF–WF transition on the conductivity of the La2CuO4 single crystal in the direction parallel to the CuO2 layers. The results provide support for the three-dimensional nature of the hopping conduction of this layered oxide.
Intrinsic and extrinsic inhomogeneities in mixed-valence manganites
Authors: Belevtsev B. I.
Published: May 2004

It is suggested that extrinsic inhomogeneities in mixed-valence manganites deserve more attention and that they should be taken into account on equal footing with the hypothetical phase separation when examinating experimental data and developing theoretical models for the influence of stoichiometric and other types of inhomogeneities on the properties of these and other transition-metal oxides.
Phase and orientational ordering of low molecular weight rod molecules in a quenched liquid crystalline polymer matrix with mobile side chains
Authors: Gutman Lorin , Cao Jianshu , Swager Tim M.
Published: May 2004

We study the phase diagram and orientational ordering of guest liquid crystalline (LC) rods immersed in a quenched host made of a liquid crystalline polymer (LCP) matrix with mobile side chains. The LCP matrix lies below the glass transition of the polymer backbone. The side chains are mobile and can align to the guest rod molecules in a plane normal to the local LCP chain contour. A field theoretic formulation for this system is proposed and the effects of the LCP matrix on LC ordering are determined numerically. We obtain simple analytical equations for the nematic/isotropic phase diagram boundaries. Our calculation show a nematic–nematic (N/N) first order transition from a guest stabilized to a guest–host stabilized region and the possibility of a reentrant transition from a guest stabilized nematic region to a host only stabilized regime separated by an isotropic phase. A detailed study of thermodynamic variables and interactions on orientational ordering and phases is carried out and the relevance of our predictions to experiments and computer simulations is presented.
Curvature elasticity of mixed amphiphilic bilayers
Authors: Gonzalez A. P.
Published: May 2004

Elastic bending constants of mixed amphiphilic bilayers are calculated using a molecular approach. The free energy is expanded up to quadratic order in curvatures and compositions, choosing a flat symmetrical bilayer as the reference state. Bending constants are then calculated from the derivatives of the free energy evaluated at this reference state. Two-component bilayers are considered. As a novelty, the local compositions are allowed to fully relax upon bending so that the 2 monolayers are at chemical equilibrium with each other at every curvature. The compositional degree of freedom is shown to affect the bending constant k, but not the saddle-splay constant k̄. The influence on the membrane elastic properties of various chain structural features, such as length, volume, and stiffness, is investigated. This may prove useful to model mixed bilayers composed of hydrocarbon/hydrocarbon and hydrocarbon/fluorocarbon chains.
Dynamics of photodissociation of ethylene and its isotopomers at 157 nm: Branching ratios and kinetic-energy distributions
Authors: Lee Shih-Huang , Lee Yuan T. , Yang Xueming
Published: May 2004

We investigated the photodissociation of ethylene and its isotopomers at 157 nm in a molecular-beam apparatus using photofragment translational spectroscopy combined with synchrotron-based photoionization. The time-of-flight (TOF) spectra of all photofragments H, H2, C2H2, C2H3, and their deuterium isotopic variants were recorded, from which kinetic-energy distributions P(Et) and branching ratios were obtained. Most C2H3 spontaneously dissociates to C2H2+H and only C2H3 with small internal energy survives. The C2H2 fragment due to H2 elimination is observed leading the C2H2 fragment due to 2H elimination in TOF distribution because the former process has more kinetic-energy release. An analogous result is observed for C2D4 photolysis. That elimination of molecular hydrogen is site-specific and is revealed from photolysis of three dideuterated ethylene isotopomers, in which an isotopic effect plays a significant role. Observations of C2D2+2H and C2H2+2D product channels in the photolysis of 1,1-CH2CD2 provide evidence for migrations of H and D atoms. A comparison with previous experimental and theoretical results is made.
A hybrid scheme for the resolution-of-the-identity approximation in second-order Møller–Plesset linear-r12 perturbation theory
Authors: Klopper Wim
Published: May 2004

In the framework of second-order Møller–Plesset linear-r12 (MP2-R12) perturbation theory, a method is developed and implemented that uses an auxiliary basis set for the resolution-of-the-identity (RI) approximation for the three- and four-electron integrals. In contrast to previous work, the two-electron integrals that must be evaluated never involve more than one auxiliary basis function. The new method therefore scales linearly with the number of auxiliary basis functions and is much more efficient than the previous one, which scaled quadratically. A general formulation of MP2-R12 theory is presented for various ansätze, approximations, and orbitals (canonical or localized). The new method is assessed by computations of the valence-shell second-order Møller–Plesset correlation energy of a few small closed-shell systems. The preliminary calculations indicate that the difference between the new and previous methods is about one order of magnitude smaller than the errors that occur due to basis-set truncations and RI approximations and under the assumptions of generalized and extended Brillouin conditions.
Dynamics of photodissociation of 3,3,3-d3-propene at 157 nm: Site effect and hydrogen migration
Authors: Lee Shih-Huang , Lee Yuan T. , Yang Xueming
Published: May 2004

In a preceding paper [Lee et al., J. Chem. Phys. 119, 827 (2003)], we measured the kinetic-energy distributions P(Et) and branching ratios of products from photolysis of propene at 157 nm using time-of-flight spectroscopy combined with photoionization. In the present work, hydrogen migration before fragmentation and a site effect on P(Et) and branching ratios were revealed from the photodissociation of CD3CHCH2. Labeling of the methyl group with deuterium enabled us to differentiate between elimination of atomic and molecular hydrogen from the vinyl moiety and from the methyl moiety; the P(Et) and relative yields for the formation of H, D, H2, HD, and D2 were measured. Deuterium labeling allowed us to also differentiate the fragmentation after hydrogen transfer from that before hydrogen migration. The observation of isotopic variants of CD3 and C2H3 radicals in the C–C bond cleavage provides evidence for hydrogen transfer of propene because of site specificity. The fraction of fragmentation after hydrogen transfer is estimated to be 25%. The isotope-specific branching ratios for five dissociation pathways of CD3CHCH2 were evaluated.
Optical nonlinearity of monodispersed, capped ZnS quantum particles
Authors: Nikesh V. V. , Dharmadhikari Aditya , Ono Hiroshi , Nozaki Shinji , Kumar G. Ravindra , Mahamuni Shailaja
Published: May 2004

ZnS quantum dots are synthesized by a high-temperature chemical route with narrow size distribution at diameters of 1.4 and 1.8 nm. Significantly small size dispersion of 1.4-nm-sized ZnS quantum dots is vivid from the transmission electron microscopic measurements. The nonlinear absorption is measured at wavelengths 532 and 520 nm using a picosecond laser in an open aperture z-scan setup. The measured two-photon absorption coefficients are 0.08 and 0.2 cm/GW for smaller and larger nanoparticles. Two photon absorption cross sections for nanoparticles are about six orders of magnitude larger than bulk ZnS.
Solvent-induced microphase separation in diblock copolymer thin films with reversibly switchable morphology
Authors: Peng Juan , Xuan Yu , Wang Hanfu , Yang Yuming , Li Binyao , Han Yanchun
Published: May 2004

We have studied the surface morphology of symmetric poly(styrene)-block-poly(methyl methacrylate) diblock copolymer thin films after solvent vapor treatment selective for poly(methyl methacrylate). Highly ordered nanoscale depressions or striped morphologies are obtained by varying the solvent annealing time. The resulting nanostructured films turn out to be sensitive to the surrounding medium, that is, their morphologies and surface properties can be reversibly switchable upon exposure to different block-selective solvents.
Simulation of the effects of chain architecture on the sorption of ethylene in polyethylene
Authors: Banaszak Brian J. , Faller Roland , de Pablo Juan J.
Published: May 2004

An osmotic ensemble hyperparallel tempering technique has been developed to study the solubility of ethylene in amorphous linear low-density polyethylene of different chain architectures. The NERD united-atom force field (Nath, Escobedo, and de Pablo revised united-atom force field) [Nath et al., J. Chem. Phys. 108, 9905 (1998); Mol. Phys. 98, 231 (2000); J. Chem. Phys. 114, 3612 (2001)] is used in all simulations. We have investigated the effect of polyethylene chain length and branching on ethylene solubility. In this study, we have considered short-chain branching of amorphous linear low-density ethylene-1-hexene copolymers under typical polymerization reactor conditions. It is observed that, in the polymer, ethylene prefers to reside in the vicinity of polymer chain ends. This clustering causes a decrease in ethylene solubility with polymer chain length. When short-chain branches are introduced to a linear polymer chain, however, the chain-end clustering effect is counteracted by a higher density, thereby leading to an ethylene solubility almost identical to that in the linear polymer.
Polymer field-effect transistors by a drawing method
Authors: Nagamatsu Shuichi , Takashima Wataru , Kaneto Keiichi , Yoshida Yuji , Tanigaki Nobutaka , Yase Kiyoshi
Published: May 2004

We demonstrated the polymer field-effect transistors (FETs) utilizing regioregular poly(3-alkylthiophene)s (P3AT) films prepared by a drawing method. The P3AT film exhibited large optical dichroic ratio, which originated in the polymer backbones aligned to the drawing direction. In-plane anisotropy and enhancement of FET characteristics have been observed that are caused by molecular alignment. In the case of poly(3-dodecylthiophene), the hole mobility along the drawing direction was enhanced by a factor of 25 compared with that of spin-coated film.
Development of very large helicon plasma source
Authors: Shinohara Shunjiro , Tanikawa Takao
Published: May 2004

We have developed a very large volume, high-density helicon plasma source, 75 cm in diameter and 486 cm in axial length; full width at half maximum of the plasma density is up to ∼42 cm with good plasma uniformity along the z axis. By the use of a spiral antenna located just outside the end of the vacuum chamber through a quartz-glass window, plasma can be initiated with a very low value of radio frequency (rf) power (<1 W), and an electron density of more than 1012 cm−3 is successfully produced with less than several hundred Watt; achieving excellent discharge efficiency. It is possible to control the radial density profile in this device by changing the magnetic field configurations near the antenna and/or the antenna radiation-field patterns.
System to monitor data analyses and results of physics data validation between pulses at DIII–D
Authors: Flanagan S. , Schachter J. M. , Schissel D. P.
Published: May 2004

A data analysis monitoring (DAM) system has been developed to monitor between pulse physics analysis at the DIII–D National Fusion Facility (http://nssrv1.gat.com:8000/dam). The system allows for rapid detection of discrepancies in diagnostic measurements or the results from physics analysis codes. This enables problems to be detected and possibly fixed between pulses as opposed to after the experimental run has concluded, thus increasing the efficiency of experimental time. An example of a consistency check is comparing the experimentally measured neutron rate and the expected neutron emission, RDD0D. A significant difference between these two values could indicate a problem with one or more diagnostics, or the presence of unanticipated phenomena in the plasma. This system also tracks the progress of MDSplus dispatched data analysis software and the loading of analyzed data into MDSplus. DAM uses a Java Servlet to receive messages, C Language Integrated Production System to implement expert system logic, and displays its results to multiple web clients via Hypertext Markup Language. If an error is detected by DAM, users can view more detailed information so that steps can be taken to eliminate the error for the next pulse.