bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarized glucose transporters and mRNA expression properties in newly developed rat syncytiotrophoblast cell lines, TR‐TBTs
Authors: Kitano Tomohide , Iizasa Hisashi , Terasaki Tetsuya , Asashima Tomoko , Matsunaga Noriko , Utoguchi Naoki , Watanabe Yoshiteru , Obinata Masuo , Ueda Masatsugu , Nakashima Emi
Published: October 2002

In this study, we have established new syncytiotrophoblast cell lines (TR‐TBTs) from the recently developed transgenic rat harboring temperature‐sensitive simian virus 40 large T‐antigen gene (Tg‐rat). Four conditionally immortalized syncytiotrophoblast cell lines (TR‐TBT 18d‐1∼4) were obtained from pregnant Tg‐rats at gestational day 18. These cell lines had a syncytium‐like morphology, could be prepared as monolayers, expressed cytokeratins and rat syncytiotrophoblast markers, and exhibited apical or basal GLUT1 localizations and apical GLUT3 localizations. TR‐TBTs express large T‐antigen and grow well at 33°C with a doubling time of about 30 h. TR‐TBTs have processes for the uptake of dehydroepiandrosteron‐3‐sulfate (DHEAS) and these are predominantly located on the basal side, and this is the first report of an in vitro model of blood placental barrier (BPB) able to incorporate DHEAS. Therefore, TR‐TBTs are an appropriate in vitro model for investigating carrier‐mediated transport functions at the BPB. Moreover, TR‐TBTs express betaine/GABA transporter (GAT‐2/BGT‐1), concentrative nucleoside transporter 2 (CNT2), equilibrative nucleoside transporter 1 (ENT1), and ENT2 and the expression of these transporters has been reported in blood–brain barrier (BBB). Thus, the expression patterns of nucleoside and neurotransmitter transporters examined are quite similar in both the BPB and BBB. © 2002 Wiley‐Liss, Inc.
The Fourier transform Coulomb method: Efficient and accurate calculation of the Coulomb operator in a Gaussian basis
Authors: Füsti-Molnár László , Pulay Peter
Published: October 2002

We describe a method for calculating the matrix elements of the Coulomb operator for Gaussian basis sets using an intermediate discrete Fourier transform of the density. Our goals are the same as those of the Gaussian and augmented-plane-wave method of Parrinello and co-workers [M. Krack and M. Parrinello, Phys. Chem. Chem. Phys. 2, 2105 (2000)], but our techniques are quite different. In particular, we aim at much higher numerical accuracy than typical programs using plane wave expansions. Our method is free of the effects of periodic images and yields full precision. Other low-scaling methods for the Coulomb operator are compared to the Fourier transform method with regard to numerical precision, asymptotic scaling with molecular size, asymptotic scaling with basis set size, onset point (the size of the calculation where the method outperforms traditional Gaussian integral techniques by a factor of 2), and the ability to calculate the Hartree–Fock exchange operator. The Fourier transform method is superior to alternatives by most criteria. In particular, for typical molecular applications it has an earlier onset point than fast multipole methods.
Role of grain boundaries on hydrogen-induced degradation in lead zirconate titanate thin films
Authors: Lee Jang-Sik , Joo Seung-Ki
Published: October 2002

It is well known that exposing lead zirconate titanate (PZT) thin films to hydrogen severely degrades the electrical properties. This phenomenon has been the subject of intensive study; however, there is no electrical evidence relating the hydrogen-induced degradation with the grain boundaries in the films. In this work, using large-grained PZT thin films (average grain size: 40 μm), we could measure the effects of grain boundary on the hydrogen-induced degradation in PZT thin films by locating the upper Pt electrode (8×8 μm2) sequentially from the center of the grain to the grain boundary in a controlled manner. It was found that the grain boundary was mainly responsible for the electrical degradation caused by exposure to the hydrogen. Little degradation with hydrogen exposure was observed when the Pt top electrode was located in the center of the grain.
MOLECULAR THEORETICAL CALCULATIONS ON TEMPERATURE DEPENDENCE OF THE PITCH OF CHOLESTERIC LIQUID CRYSTALS
Authors: ZHANG ZHIDONG , LI ZHIGUANG , LIU JINGLI
Published: October 2002

The temperature-dependent pitch of a cholesteric phase is studied using both molecular field theory and the two-particle cluster theory. The interacting chiral molecules (as derived by van der Meer et al.) are placed at the sites of a three-dimensional, simple cubic lattice with orientations confined to two dimensions. The equilibrium pitch as functions of temperature is calculated and numerical results are compared with those predicted by Monte Carlo computer simulation. The two-particle cluster theory, taking into account short-range correlations between molecules, yields improved values compared with molecular field theory.
IMAGE SEGMENTATION WITH ASTEROIDALITY/TUBULARITY AND SMOOTHNESS CONSTRAINTS
Authors: CHEN DANNY Z. , WANG JIE , WU XIAODONG
Published: October 2002

Image segmentation with specific constraints has found applications in several areas such as biomedical image analysis and data mining. In this paper, we study the problem of segmenting star-shaped and smooth objects in 2-D and tubular objects in 3-D images. Image objects of these shapes are often studied in medical applications. For the 2-D case of the problem, we present an O(IJ log J) time algorithm, improving the previously best known O(IJ2M) time algorithm by a factor of [Formula: see text] time, where the size of the input 2-D image is I × J and M is the smoothness parameter with 1 ≤ M ≤ J. Our 2-D algorithm is based on a combination of dynamic programming and divide-and-conquer strategy, and on computing an optimal path in an implicitly represented graph. We also prove that a generalized version of the 3-D case of the problem is NP-hard.
CD14+,CD16+ blood monocytes and joint inflammation in rheumatoid arthritis
Authors: Kawanaka Norikuni , Yamamura Masahiro , Aita Tetsushi , Morita Yoshitaka , Okamoto Akira , Kawashima Masanori , Iwahashi Mitsuhiro , Ueno Akiko , Ohmoto Yasukazu , Makino Hirofumi
Published: October 2002

Objective

CD14+,CD16+ monocytes, identified as a minor population of monocytes in human peripheral blood (PB), have been implicated in several inflammatory diseases. We undertook this study to investigate the relevance of this phenotype to joint inflammation in rheumatoid arthritis (RA).

Methods

The expression of CD14, CD16, CC chemokine receptor 1 (CCR1), CCR5, and intercellular adhesion molecule 1 (ICAM‐1) on monocytes was measured by flow cytometric analysis. Concentrations of the cytokines known to induce CD16 (including transforming growth factor β1 [TGFβ1], macrophage colony‐stimulating factor [M‐CSF], and interleukin‐10 [IL‐10]) and concentrations of the soluble form of CD14 (sCD14) in plasma and synovial fluid (SF) samples were measured by enzyme‐linked immunosorbent assay. The induction of CD16 on RA blood monocytes cultured for 18 hours with 1 or with all 3 cytokines was determined.

Results

The mean ± SD frequency of CD14+,CD16+ blood monocytes was significantly increased in RA patients (11.7 ± 5.6%; n = 105) compared with healthy controls (9.5 ± 2.2%; n = 15) (P < 0.01), and the patient group with an increased frequency of CD16+ monocytes (≥13.9%) had active disease, as defined by increased counts of tender and swollen joints, levels of acute‐phase reactants, and titers of rheumatoid factor. The response to drug therapy correlated with changes in the frequency of this phenotype. The expression of CD16 on SF monocytes from RA patients was markedly elevated compared with the expression on PB monocytes. CD16 expression on RA blood monocytes was augmented in vitro by IL‐10, M‐CSF, and TGFβ1. Plasma concentrations of these cytokines and of sCD14 were significantly higher in RA patients with high CD16+ monocyte frequencies than in those with low CD16+ monocyte frequencies or in healthy controls. CD14+,CD16+ monocytes expressed higher levels of CCR1, CCR5, and ICAM‐1 than did regular CD14++,CD16− monocytes, particularly in active RA.

Conclusion

These results indicate that the maturation of blood monocytes into tissue‐infiltrative CD16+ cells before entry into the joint, induced by cytokine spillover from the inflamed joint, may contribute to the persistent joint inflammation of RA.
Significant increases in serum and plasma concentrations of matrix metalloproteinases 3 and 9 in patients with rapidly destructive osteoarthritis of the hip
Authors: Masuhara Kensaku , Nakai Tsuyoshi , Yamaguchi Katsuyuki , Yamasaki Satoshi , Sasaguri Yasuyuki
Published: October 2002

Objective

Rapidly destructive osteoarthritis (OA) of the hip is an uncommon subset of OA that affects mainly elderly women. Previous studies indicate that elevated levels of matrix metalloproteinases (MMPs) are produced within the tissue of patients with the condition. In the present study, we sought to determine whether serum and plasma levels of MMPs and tissue inhibitors of metalloproteinases (TIMPs) are also elevated.

Methods

Blood samples were obtained from 16 patients with rapidly destructive hip OA and from 20 patients with OA before total hip arthroplasty was performed. Synovial specimens were obtained during surgery. Synovial fibroblasts that had migrated sufficiently from explants were subcultured in vitro for 72 hours after confluency, and harvested supernatants were collected. Blood, tissue samples, and fibroblasts were assayed for MMPs 1, 2, 3, and 9, and TIMPs 1 and 2 by sandwich enzyme immunoassay.

Results

In blood samples, the levels of MMP‐3 and MMP‐9 in the group with rapidly destructive hip OA were significantly higher than the normal range and were also significantly higher than those in the OA group. In tissue samples, the levels of MMP‐1, MMP‐3, MMP‐9, and TIMP‐1 in the group with rapidly destructive hip OA were significantly higher than those in the OA group.

Conclusion

The results of this study show that serum and plasma levels of MMP‐3 and MMP‐9 are significantly increased in patients with rapidly destructive hip OA. Significantly large amounts of these MMPs produced in synovial tissues within the hip joint could contribute in part to elevation of blood levels. Detection of increased levels of MMP‐3 and MMP‐9 in patients with painful, disabling hip OA may be of diagnostic value for rapidly destructive hip OA.
Evidence for linkage of HLA loci in juvenile idiopathic oligoarthritis: Independent effects of HLA–A and HLA–DRB1
Authors: Zeggini Eleftheria , Donn Rachelle P. , Ollier William E. R. , Thomson Wendy ,   The British Paediatric Rheumatology Study Group
Published: October 2002

Objective

Although multiple associations between HLA loci and juvenile oligoarthritis have previously been documented, evidence for linkage of HLA loci in oligoarthritis in UK Caucasians with juvenile idiopathic arthritis (JIA) has not been described. The aim of this study was to investigate linkage of HLA–A, B, and DRB1 in UK Caucasian JIA patients with oligoarthritis.

Methods

One hundred forty‐two families comprising affected offspring and their parents (45 with one parent available and 97 with both parents available) were typed for HLA–A, B, and DRB1 by polymerase chain reaction–sequence‐specific oligonucleotide probe. Single‐point and multipoint analyses were performed using various modifications of the extended transmission disequilibrium test. Linkage disequilibrium (LD) analysis was performed using the EH‐Plus system.

Results

Linkage to HLA–A and HLA–DRB1 was seen in oligoarthritis and in the International League of Associations for Rheumatology–defined subgroups of persistent oligoarthritis and extended oligoarthritis. Linkage to HLA–A, B, and DRB1 was also observed in female patients with oligoarthritis. Linkage of the HLA loci seemed to be attributable to maternal preferential transmission of alleles. Furthermore, LD patterns between the HLA–A, B, and DRB1 loci were investigated. HLA–A and HLA–DRB1 were confirmed as independent susceptibility loci for oligoarthritis.

Conclusion

This is the first study to establish linkage of HLA–A and HLA–DRB1 in oligoarthritis and to show that the 2 loci contribute independently to disease. Further studies are being performed to determine whether it is these loci or other genes in LD with them that are responsible for susceptibility to oligoarthritis in UK Caucasian patients with JIA.
Simulation of digital earthquake accelerograms using the inverse discrete Fourier transform
Authors: Thráinsson Hjörtur , Kiremidjian Anne S.
Published: October 2002

Acceleration time histories of horizontal earthquake ground motion are obtained by inverting the discrete Fourier transform, which is defined by modelling the probability distribution of the Fourier phase differences conditional on the Fourier amplitude.

The Fourier amplitude spectrum is modelled as a scaled, lognormal probability density function. Three parameters are necessary to define the Fourier amplitude spectrum. They are the total energy of the accelerogram, the central frequency, and the spectral bandwidth.

The Fourier phase differences are simulated conditional on the Fourier amplitudes. The amplitudes are classified into three categories: small, intermediate and large. For each amplitude category, a beta distribution or a combination of a beta distribution and a uniform distribution are defined for the phase differences. Seven parameters are needed to completely define the phase difference distributions: two for each of the three beta distributions, and the weight of the uniform distribution for phase differences corresponding to small Fourier amplitudes.

Approximately 300 uniformly processed horizontal ground motion records from recent California earthquakes are used to develop prediction formulas for the model parameters, as well as to validate the simulation model. The moment magnitude of the earthquakes ranges from 5.8 to 7.3. The source to site distance for all the records is less than 100 km. Copyright © 2002 John Wiley & Sons, Ltd.
Survival analysis of endometrial carcinoma associated with hereditary nonpolyposis colorectal cancer
Authors: Boks Dominique E.S. , Trujillo Aliana P. , Voogd Adri C. , Morreau Hans , Kenter Gemma G. , Vasen Hans F.A.
Published: October 2002

Endometrial carcinoma (EC) is the most common extracolonic tumor associated with hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC increases the risk of EC compared to the general population. Patients with HNPCC have a better prognosis than patients with common sporadic colorectal cancer. It is unknown, however, whether the survival rate of HNPCC‐associated EC is higher than that of sporadic EC. The aim of our study was to compare the survival rates of HNPCC‐associated EC with sporadic EC. From the registry of the Netherlands Foundation for Hereditary Tumors, 50 patients with HNPCC‐associated EC from 46 families harboring a germline mutation or fulfilling the Amsterdam Criteria II were age‐ and stage‐matched with 100 patients with sporadic EC registered in the Eindhoven Cancer Registry in the Netherlands. Survival rates were analyzed. The overall 5‐year cumulative survival rates for patients with HNPCC‐associated EC was 88% and 82% for patients with sporadic EC (p = 0.59). In Stages IA, IB and IC, the survival rates of patients with HNPCC‐associated EC and sporadic EC were 92% and 91%, respectively (p = 0.90). In Stages IIIA and IIIC, the survival rates for HNPCC‐associated EC and sporadic EC were 72% and 50%, respectively (p = 0.38). Furthermore, there was no significant difference in the distribution of tumor histologic subtypes in the study and control groups (p = 0.55). The outcomes in survival in EC in the general population and in women from families with HNPCC do not differ significantly. These results may have important implications in our understanding of EC and the role of early screening. © 2002 Wiley‐Liss, Inc.
Gender effects in familial cancer
Authors: Hemminki Kari , Li Xinjun
Published: October 2002

Very limited data are available on sex ratios in familial cancer. Such data would be valuable in the assessment of sex chromosome effects and of interactions between background and familial rates. We used the nationwide Swedish Family‐Cancer Database on 10.2 million individuals and over 1 million neoplasms to analyze familial risks for male and female offspring by paternal and maternal concordant cancer. Sex ratios for familial cancer were derived for cancer at 15 sites shared by men and women. At 14 sites the sex ratio (male/female) for familial relative risk ranged between 0.78 and 1.41, with no evidence of sex preference, suggesting that sex chromosomes do not contribute to a noticeable extent to familial risks. Furthermore, in cancers where the background incidence varied extensively by sex, such as bladder cancer (sex ratio 2.82) and nonthyroid endocrine tumors (0.65), the familial effect was proportionate to the background incidence and the familial sex ratio was close to unity. In thyroid cancer, the familial sex ratio was 2.48 (1.54–3.98) and the background incidence ratio was 0.31. This was the first evidence of an inverse sex ratio in primary cancer, i.e., higher familial risk in the gender of low background risk. The high familial ratio, 2.85 (95% CI: 1.35–6.03), was due to thyroid adenocarcinoma, encompassing both papillary and follicular types. © 2002 Wiley‐Liss, Inc.
Emerging functions of p21‐activated kinases in human cancer cells
Authors: Kumar Rakesh , Vadlamudi Ratna K.
Published: October 2002

The p21 activated kinases (Paks), an evolutionarily conserved family of serine/threonine kinases, are important for a variety of cellular functions including cell morphogenesis, motility, survival, mitosis, and angiogenesis. Paks are widely expressed in numerous tissues and are activated by growth factors and extracellular signals through GTPase‐dependent and ‐independent mechanisms. Overexpression of Paks in epithelial cancer cells has been shown to increase migration potential, increase anchorage independent growth, and cause abnormalities in mitosis. Dysregulation of Paks has been reported in several human tumors and neurodegenerative diseases. A growing list of novel Pak interacting proteins has opened up exciting avenues of investigation by which to understand the functions of Paks in tumorigenesis. In this review, we will summarize the current knowledge of the Paks family with respect to emerging cellular functions and possible contributions to cancer. © 2002 Wiley‐Liss, Inc.
Lipopolysaccharide‐induced reductions in cellular coupling correlate with tyrosine phosphorylation of connexin 43
Authors: Lidington Darcy , Tyml Karel , Ouellette Yves
Published: October 2002

We have previously shown in cultured rat microvascular endothelial cells (RMEC) that lipopolysaccharide (LPS) stimulates a protein tyrosine kinase (PTK)‐dependent reduction in cellular coupling. We hypothesized that connexin 43 (Cx43) becomes phosphorylated following exposure to LPS. Cx43 was immunoprecipitated from control and LPS‐treated RMEC monolayers. Tyrosine phosphorylation of Cx43, detected by immunoblot, was found only in the LPS treatment. To verify these results, Cx43 was radiolabeled with [32P]‐orthophosphate. Radiolabeled Cx43 exhibited a slight increase in phosphorylation in response to LPS; phosphoamino acid analysis displayed equivalent amounts of phosphoserine in control and LPS treatments, but detected phosphotyrosine only in the LPS treatment. The PTK inhibitors PP‐2 (10 nM) and geldanamycin (200 nM) were found to block the response to LPS in terms of Cx43 tyrosine phosphorylation and cellular coupling. The phosphatase inhibitor BpV (1 μM) accentuated the effect of LPS, while the putative phosphatase activator C6‐ceramide prevented it. When measuring cell communication, phosphatase inhibition also blocked the reversal of the LPS response following LPS washout. We conclude that Cx43 is tyrosine phosphorylated following exposure to LPS and suggest that the LPS‐induced increase in intercellular resistance may be mediated by tyrosine phosphorylation of this connexin. Altering tyrosine kinase and phosphatase activities can modulate the LPS‐induced tyrosine phosphorylation of Cx43 and reductions in cellular coupling. J. Cell. Physiol. 193: 373–379, 2002. © 2002 Wiley‐Liss, Inc.
Cellular distribution of oxygen sensor candidates—Oxidases, cytochromes, K+‐channels—in the carotid body
Authors: Kummer Wolfgang , Yamamoto Yoshio
Published: October 2002

The specific tissue of the carotid body is built up of groups of glomus cells, enveloped by glial‐type sustentacular cells, and innervated by sensory nerve fibers. These units sense arterial pO2 and respond to hypoxia by a variety of reactions that include initiation of the arterial chemoreflex, i.e., increasing firing activity in the carotid sinus nerve. Until now, neither the cellular localization of the initial events that lead to stimulation of chemoreceptor afferents nor the molecular mechanism of oxygen sensing in the carotid body have been unequivocally identified. Proposed molecular candidates for the mechanism of oxygen sensing include: 1) components of the mitochondrial respiratory chain, 2) NADPH oxidases generating reactive oxygen species in an oxygen‐dependent manner, 3) oxygen‐regulated plasmalemmal K+‐channels, and 4) nonoxidase iron‐proteins. Our still limited knowledge on their cellular distribution within the carotid body is reviewed here. It is evident that: 1) the distribution of at least some oxygen sensor candidates is not ubiquitous but cell‐type‐specific, and 2) each specific parenchymal cell type of the carotid body contains at least one of the proposed oxygen sensor candidates. This applies also for the glial‐type sustentacular cells that exhibit immunoreactivity to the two‐pore domain K+‐channel, TASK‐1. These observations fit best with the assumption that each cell type within the carotid body is principally responsive to hypoxia. The differential equipping of glomus cells, nerve endings, and sustentacular cells with sensor proteins might serve to determine different thresholds of sensitivity and/or to connect the process of oxygen sensing to different signaling pathways. It also favors the assumption that several mechanisms of oxygen sensing may act simultaneously. The cellular identification of the cell type initiating the chemoreceptor reflex, however, has to await the molecular identification of the particular oxygen sensor molecule that initiates increased carotid sinus nerve activity. Microsc. Res. Tech. 59:234–242, 2002. © 2002 Wiley‐Liss, Inc.
Carotid body chemoreceptors in dissociated cell culture
Authors: Nurse C.A. , Fearon I.M.
Published: October 2002

Carotid body (CB) glomus or type 1 cells act as peripheral chemoreceptors which detect changes in arterial PO2, PCO2, and pH and help maintain homeostasis via the reflex control of ventilation. Over the last ∼12 years significant progress has been made towards understanding chemotransduction mechanisms using freshly isolated or cultured type 1 cells. The latter preparation allows several powerful experimental manipulations (e.g., co‐culture with sensory neurons) resulting in significant advances in our understanding of CB chemoreception. Here, we review several properties of type 1 cells after several days to weeks in culture. Typically, cultured type 1 cells grow in monolayer clusters enveloped by glial‐like, type II, or sustentacular cells, which are immunopositive for the glial marker, glial fibrillary acid protein (GFAP). These cells can undergo DNA synthesis, evidenced by uptake of bromodeoxyuridine (BrdU), and show a limited capacity for cell division. Mitosis and survival of type 1 cells can be regulated by oxygen tension and/or growth factors (e.g., bFGF, insulin). In the rat, type 1 cells are immunopositive for several monoaminergic markers, including tyrosine hydroxylase (TH), dopamine transporter (DAT), and 5‐HT. They also express cholinergic markers (e.g., vesicular acetylcholine transporter; VAChT), the highly conserved synaptic vesicle protein (SV2), and gap junctional proteins including Connexin 32 (Cx32). Moreover, in long‐term culture (∼2 weeks) they retain expression of O2‐sensitive, TASK‐1‐like, and Ca2+‐dependent (BK), K+ channels as revealed by immunocytochemistry or RT‐PCR analysis of mRNA extracted from type 1 clusters after removal from the culture surface. Microsc. Res. Tech. 59:249–255, 2002. © 2002 Wiley‐Liss, Inc.
Spatiotemporal intermittency in the torsional Couette flow between a rotating and a stationary disk
Authors: Cros A. , Le Gal P.
Published: October 2002

This work is devoted to the experimental study of the transition to turbulence of a flow confined in a narrow gap between a rotating and a stationary disk. When the fluid layer thickness is of the same order of magnitude as the boundary layer depths, the azimuthal velocity axial gradient is nearly constant and this rotating disk flow tends to be a torsional Couette flow. As in the plane Couette flow or the Taylor–Couette flow, transition to turbulence occurs via the appearance of turbulent domains inside a laminar background. In the rotating disk case, the nucleation of turbulent spirals, previously called “solitary waves” in the rotating disk flow literature, is connected to the birth of structural defects in a periodic underlying roll pattern. As the rotation rate is increased, the lifetime of these turbulent structures increases until a threshold is reached where they then form permanent turbulent spirals arranged nearly periodically all around a circumference. However, since the number of these turbulent spirals decreases with the rotational frequency, the transition to a fully turbulent regime is not achieved. Thus the turbulent fraction of the pattern saturates to a value lower than 0.5. After a geometrical description of the structures, we present a statistical analysis of sizes and lifetimes of the turbulent and laminar domains in order to compare this transition to already observed spatiotemporal intermittent behavior.
Fusion and toroidal formation of vesicles by mechanical forces: A Brownian dynamics simulation
Authors: Noguchi Hiroshi
Published: October 2002

We studied the morphological change in bilayer vesicles induced by mechanical forces using a Brownian dynamics simulation. When bilayer membranes in two vesicles or the same vesicle are pushed from both sides by two nanoparticles, they fuse into a spherical or toroidal vesicle, respectively. Under large forces, the fusion occurs directly after the contact of the distal (trans) monolayers. Stochastically, a fusion intermediate, a disk-shaped bilayer consisting of both inner monolayers is formed under weaker forces. In this intermediate, the fusion pore that connects the insides of the vesicles is formed at the edge of the bilayer disk. These fusion processes are different from those of spontaneous fusion. The toroidal vesicle spontaneously changes back into a spherical shape, because the vesicle is small. The hole of the toroid disappears through a cylindrical stalk.
Scanning force microscopy investigation of the Pb(Zr0.25Ti0.75)O3/Pt interface
Authors: Lu X. M. , Schlaphof F. , Grafström S. , Loppacher C. , Eng L. M. , Suchaneck G. , Gerlach G.
Published: October 2002

We report on a novel approach for the investigation of the Pb(ZrxTi1−x)O3/Pt interface applying scanning force microscopy techniques. Ferroelectric samples (PZT film /Pt/SiO2/Si) were polished at a shallow angle (∼6.1°) thereby enlarging the film cross section from a 430 nm film thickness to a width of more than 4 μm. Piezoresponse force microscopy and Kelvin probe force microscopy were applied in order to deduce the dielectric polarization P and local potential distribution over the full cross section. We clearly observe a transition layer with a thickness of ∼240 nm which manifests itself both in a gradual decrease of the piezoresponse signal as a function of film thickness and in a corresponding variation of the surface potential. Furthermore, after polarization reversal due to a dc voltage applied to the tip, a different retention behavior was observed within the transition layer. The results are tentatively attributed to negatively charged defects accumulated at the PZT/Pt interface.
Carbon nanotube memory devices of high charge storage stability
Authors: Cui J. B. , Sordan R. , Burghard M. , Kern K.
Published: October 2002

Molecular memory devices with semiconducting single-walled carbon nanotubes constituting a channel of 150 nm in length are described. Data storage is achieved by sweeping gate voltages in the range of 3 V, associated with a storage stability of more than 12 days at room temperature. By annealing in air or controlled oxygen plasma exposure, efficient switching devices could be obtained from thin nanotube bundles that originally showed only a small gate dependence of conductance.
Encapsulation of phosphorus dopants in silicon for the fabrication of a quantum computer
Authors: Oberbeck L. , Curson N. J. , Simmons M. Y. , Brenner R. , Hamilton A. R. , Schofield S. R. , Clark R. G.
Published: October 2002

The incorporation of phosphorus in silicon is studied by analyzing phosphorus δ-doped layers using a combination of scanning tunneling microscopy, secondary ion mass spectrometry, and Hall effect measurements. The samples are prepared by phosphine saturation dosing of a Si(100) surface at room temperature, a critical annealing step to incorporate phosphorus atoms, and subsequent epitaxial silicon overgrowth. We observe minimal dopant segregation (∼5 nm), complete electrical activation at a silicon growth temperature of 250 °C and a high two-dimensional electron mobility of ∼102 cm2/V s at a temperature of 4.2 K. These results, along with preliminary studies aimed at further minimizing dopant diffusion, bode well for the fabrication of atomically precise dopant arrays in silicon such as those found in recent solid-state quantum computer architectures.
Tunneling through arbitrary potential barriers and the apparent barrier height
Authors: Probst Oliver M.
Published: October 2002

A simple matrix formalism is presented that allows the tunneling current between two planar electrodes with an arbitrary barrier potential to be calculated conveniently. This formalism is a straightforward extension of the usual textbook example for tunneling through a rectangular barrier and can be easily implemented on a personal computer. A first principles derivation of the tunneling current based on free-electron electrodes is given that is useful for the teaching of solid-state physics. Examples showing the utility of the method are the transmission through a tunnel barrier modified by the image potential and tunneling via intermediate states (resonances). These issues are interesting topics in scanning tunneling microscopy where both phenomena are believed to contribute to the image formation.
Inhibition of interleukin‐1 but not tumor necrosis factor suppresses neovascularization in rat models of corneal angiogenesis and adjuvant arthritis
Authors: Coxon Angela , Bolon Brad , Estrada Juan , Kaufman Stephen , Scully Sheila , Rattan Alana , Duryea Diane , Hu Yi‐Ling , Rex Karen , Pacheco Efrain , Van Gwyneth , Zack Debra , Feige Ulrich
Published: October 2002

Objective

To assess the capacities of the cytokine inhibitors interleukin‐1 receptor antagonist (IL‐1Ra; anakinra) and PEGylated soluble tumor necrosis factor receptor I (PEG sTNFRI; pegsunercept) to suppress neovascularization.

Methods

A corneal angiogenesis assay was performed by implanting nylon discs impregnated with an angiogenic stimulator (basic fibroblast growth factor or vascular endothelial growth factor) into one cornea of female Sprague‐Dawley rats. Animals were treated with IL‐1Ra or PEG sTNFRI for 7 days, after which new vessels were quantified. In a parallel study, male Lewis rats with mycobacteria‐induced adjuvant‐induced arthritis were treated with IL‐1Ra or PEG sTNFRI for 7 days beginning at disease onset, after which scores for inflammation and bone erosion as well as capillary counts were acquired from sections of arthritic hind paws.

Results

Treatment with IL‐1Ra yielded a dose‐dependent reduction in growth factor–induced corneal angiogenesis, while PEG sTNFRI did not. IL‐1Ra, but not PEG sTNFRI, significantly reduced the number of capillaries in arthritic paws, even though both anticytokines reduced inflammation and bone erosion to a similar degree.

Conclusion

These data support a major role for IL‐1, but not TNFα, in angiogenesis and suggest that an additional antiarthritic mechanism afforded by IL‐1 inhibitors, but not anti‐TNF agents, is the suppression of the angiogenic component of pannus.
On the advantage of haplotype analysis in the presence of multiple disease susceptibility alleles
Authors: Morris Richard W. , Kaplan Norman L.
Published: October 2002

We investigated the effect of multiple susceptibility alleles at a single disease locus on the statistical power of a likelihood ratio test to detect association between alleles at a marker locus and a disease phenotype in a case‐control design. Using simplifying assumptions to obtain the joint frequency distribution of marker and disease locus alleles, we present numerical results that illustrate the impact of historical variation of initial associations between marker alleles and susceptibility alleles on the power of a likelihood ratio test for association. Our results show that an increase in the number of susceptibility alleles produces a decrease in power of the likelihood ratio test. The decrease in power in the presence of multiple susceptibility alleles, however, is less for markers with multiple alleles than for markers with two alleles. We investigate the implications of this observation for tests of association based on haplotypes made up of tightly linked single‐nucleotide polymorphisms (SNPs). Our results suggest that an analysis based on haplotypes can be advantageous over an analysis based on individual SNPs in the presence of multiple susceptibility alleles, particularly when linkage disequilibria between SNPs is weak. The results provide motivation for further development of statistical methods based on haplotypes for assessing the potential for association methods to identify and locate complex disease genes. Genet. Epidemiol. 23:221–233, 2002. © 2002 Wiley‐Liss, Inc.
Chronic hypoxia‐induced morphological and neurochemical changes in the carotid body
Authors: Wang Zun‐Yi , Bisgard Gerald E.
Published: October 2002

The carotid body (CB) plays an important role in the control of ventilation. Type I cells in CB are considered to be the chemoreceptive element which detects the levels of PO2, PCO2, and [H+] in the arterial blood. These cells originate from the neural crest and appear to retain some neuronal properties. They are excitable and produce a number of neurochemicals. Some of these neurochemicals, such as dopamine and norepinephrine, are considered to be primarily inhibitory to CB function and others, such as adenosine triphosphate, acetylcholine, and endothelin, are thought to be primarily excitatory. Chronic hypoxia (CH) induces profound morphological as well as neurochemical changes in the CB. CH enlarges the size of CB and causes hypertrophy and mitosis of type I cells. Also, CH changes the vascular structure of CB, including inducing marked vasodilation and the growth of new blood vessels. Moreover, CH upregulates certain neurochemical systems within the CB, e.g., tyrosine hydroxylase and dopaminergic activity in type I cells. There is also evidence that CH induces neurochemical changes within the innervation of the CB, e.g., nitric oxide synthase. During CH the sensitivity of the CB chemoreceptors to hypoxia is increased but the mechanisms by which the many CH‐induced structural and neurochemical changes affect the sensitivity of CB to hypoxia remains to be established. Microsc. Res. Tech. 59:168–177, 2002. © 2002 Wiley‐Liss, Inc.
Carotid labyrinth of amphibians
Authors: Kusakabe Tatsumi
Published: October 2002

The amphibian carotid labyrinth is a characteristic maze‐like vascular expansion at the bifurcation of the common carotid artery into the internal and external carotid arteries. The carotid labyrinths of anurans are spherical and those of urodeles are oblong. In the intervascular stroma of both anuran and urodelan carotid labyrinths, the glomus cells (type I cells, chief cells) are distributed singly or in clusters between connective tissue cells and smooth muscle cells. In fluorescence histochemistry, the glomus cells emit intense fluorescence for biogenic monoamines. In fine structure, the glomus cells are characterized by a number of dense‐cored vesicles in their cytoplasm. The glomus cells have long, thin cytoplasmic processes, some of which are closely associated with smooth muscle cells, endothelial cells, and pericytes. Afferent, efferent, and reciprocal synapses are found on the glomus cells. The morphogenesis of the carotid labyrinth starts in the larvae at the point where the carotid arch descends to the internal gills. Through the early stages of larval development, the slightly expanded region of the external carotid artery becomes closely connected with the carotid arch. By the end of the foot stage, the expanded region becomes globular, and at the final stage of metamorphosis the carotid labyrinth is close to its adult form. In fine structure, the glomus cells appear as early as the initial stage of larval development. At the middle stages of development, the number of dense‐cored vesicles increases remarkably. Distinct afferent synapses are found in juveniles, although efferent synapses can be seen during metamorphosis. The carotid labyrinth is innervated by nerve fibers containing several kinds of regulatory neuropeptides. Double‐immunolabeling in combination with a multiple dye filter system demonstrates the coexistence of two different neuropeptides. The amphibian carotid labyrinth has been electrophysiologically confirmed to have arterial chemo‐ and baroreceptor functions analogous to those of the mammalian carotid body and carotid sinus. The ultrastructural characteristics of the glomus cells during and after metamorphosis suggest that the glomus cells contribute to the chemoreception after metamorphosis. The three‐dimensional fine structure of vascular corrosion casts suggests that the amphibian carotid labyrinth has the appropriate architecture for controlling vascular tone and the findings throughout metamorphosis reveal that the vascular regulatory function begins at an early stage of metamorphosis. In addition, immunohistochemical studies suggest that the vascular regulation in the carotid labyrinth is under peptidergic innervation. Thus, the multiple functions of the carotid labyrinth underline the importance of this relatively small organ for maintenance of homeostasis and appropriate blood supply to the cephalic region. Microsc. Res. Tech. 59:207–226, 2002. © 2002 Wiley‐Liss, Inc.
Shape complexity of whole-field three-dimensional space–time fluid interfaces in turbulence
Authors: Catrakis Haris J. , Aguirre Roberto C. , Ruiz-Plancarte Jesus , Thayne Robert D.
Published: October 2002

A shape-complexity measure, Ωd(λ), is proposed to quantify the behavior of turbulence-generated fluid interfaces in d dimensions as a function of scale λ in terms of a generalized area-volume ratio. This shape complexity provides a dimensionless measure of the interfacial contributions at scales larger than or equal to λ. This is useful, for example, to quantify the interfacial area in three dimensions or the contour length in two dimensions, facilitating a comparison of three-dimensional interfaces to two-dimensional interfacial transects. Application to mixed-fluid interfaces derived from three-dimensional ∼10003 space–time measurements above the mixing transition in turbulent jets, at Reynolds number Re∼20 000 and Schmidt number Sc∼2000, shows that both Ω3(λ) and Ω2(λ) increase continuously with decreasing scale and have scaling exponents αΩ3 and αΩ2 which depend on scale. It is argued that this scale dependence corresponds to the cumulative interfacial dynamics and structure. At intermediate scales, the shape-complexity exponent of the space–time interfaces is found to be larger in three dimensions compared to two dimensions, i.e., αΩ3(λ)>αΩ2(λ), consistent with previous comparisons between two-dimensional and one-dimensional interfacial transects. This behavior is attributable to the relative contributions of large-scale folding and small-scale wrinkling to the interfacial shape complexity, and may be expected to be Reynolds-number and Schmidt-number dependent. The shape complexity Ωd(λ) provides a way to compare quantitatively the behavior of interfaces across the range of scales and in different dimensions, in a given flow or in different flows.
Rotationally resolved structures in the fifth and sixth torsional states of Ã 1A″ acetaldehyde: Internal rotation above the torsional barrier
Authors: Chou Yung-Ching , Huang Cheng-Liang , Chen I-Chia , Ni Chi-Kung , Kung A. H.
Published: October 2002

The fluorescence excitation spectrum of acetaldehyde in its transition Ã 1A″–X̃ 1A′ is analyzed for torsional states above the barrier. States with torsional vibrational quantum numbers vt=5A, 5E, and 6A at term energies 660–927 cm−1 are assigned. This region is 100–370 cm−1 above the torsional barrier. These states lie between the limits of torsional vibrational motion and free internal rotor motion, so that the close-lying 5A2 and 6A1 states mix for K>0, and K states in the E sublevel are widely split. From an analysis of calculated eigenfunctions, the composition of K=1 sublevels reaches nearly equal proportions of odd (A2) and even (A1) torsional wave functions when levels exceed the top of the torsional barrier, whereas the K=1 eigenfunctions of vt=4A1 lying near consists of mostly even (A1) functions. Avoided crossings with ΔK=0 and Δm=0 mod 3 selection rules are observed between K=2, E sublevels of 140+154 and 140+155 and between K=2, E sublevels of 140−154 and 140−155. The K energy-level structure of 140+155 deviates significantly from the expected parabolic shape. The K structures and the K state at the lowest energy differ appreciably for the two inversion doublets 140+ and 140−.
Surface phase transformation kinetics: A geometrical model for thin films of nonvolatile and volatile solids
Authors: Safarik D. J. , Mullins C. B.
Published: October 2002

We present a model of phase transformation kinetics at the surface of nonvolatile and volatile solids, with special consideration of finite specimen size in one dimension. For nonvolatile materials in which nucleation occurs randomly and homogeneously throughout the sample, a slowing of surface phase change kinetics is predicted as specimen thickness decreases. This deceleration originates from a reduction in the number of grains contributing to surface transformation and the progressively more two-dimensional growth geometry of each grain as the sample becomes thinner. Sublimation increases the relative impingement velocity of subsurface nucleated grains and the interface, thus accelerating surface phase change (versus nonvolatile materials) in the absence of thickness effects. In thin films, the accelerating influence of sublimation competes with the retarding effect of finite specimen size, and thus transformation kinetics can be faster or slower than for nonvolatile materials, depending upon sample thickness. Finally, the model is fit to experimental data for the crystallization of volatile amorphous solid water films of varying thickness. Good agreement between experiment and theory is found, suggesting that our model captures the essential physics of simultaneous surface phase change and sublimation for finite specimens.
Numerical simulation of the onset of dynamo action in an experimental two-scale dynamo
Authors: Tilgner A.
Published: October 2002

A recent experiment [R. Stieglitz and U. Müller, Phys. Fluids 13, 561 (2001)] has demonstrated dynamo action in a sodium flow organized on two length scales. This paper reports on numerical computations of the critical conditions for dynamo onset in that experiment. Despite numerous simplifications, numerical and experimental results are in satisfactory agreement concerning the critical flow rates and the shape of the large scale magnetic field.
GaN homoepitaxy on freestanding (11̄00) oriented GaN substrates
Authors: Chen C. Q. , Gaevski M. E. , Sun W. H. , Kuokstis E. , Zhang J. P. , Fareed R. S. Q. , Wang H. M. , Yang J. W. , Simin G. , Khan M. A. , Maruska Herbert-Paul , Hill David W. , Chou Mitch M. C. , Chai Bruce
Published: October 2002

We report homoepitaxial GaN growth on freestanding (11̄00) oriented (M-plane GaN) substrates using low-pressure metalorganic chemical vapor deposition. Scanning electron microscopy, atomic-force microscopy, and photoluminescence were used to study the influence of growth conditions such as the V/III molar ratio and temperature on the surface morphology and optical properties of the epilayers. Optimized growth conditions led to high quality (11̄00) oriented GaN epilayers with a smooth surface morphology and strong band-edge emission. These layers also exhibited strong room temperature stimulated emission under high intensity pulsed optical pumping. Since for III-N materials the (11̄00) crystal orientation is free from piezoelectric or spontaneous polarization electric fields, our work forms the basis for developing high performance III-N optoelectronic devices.
Oxygen tracer studies of ferroelectric fatigue in Pb(Zr,Ti)O3 thin films
Authors: Schloss Lawrence F. , McIntyre Paul C. , Hendrix Bryan C. , Bilodeau Steven M. , Roeder Jeffrey F. , Gilbert Stephen R.
Published: October 2002

Long-range oxygen motion has been observed in Pt/Pb(Zr,Ti)O3/Ir thin-film structures after electrical fatigue cycling at room temperature. Through an exchange anneal, isotopic O18 was incorporated as a tracer into bare Pb(Zr,Ti)O3 (PZT) films, allowing secondary ion mass spectrometry measurements of the tracer profile evolution as a function of the number of polarization reversals. Observation of O18 tracer redistribution during voltage cycling, which is presumably mediated by oxygen vacancy motion, was found to be strongly dependent upon the thermal history of the film. However, there was no strong correlation between the extent of O18 tracer redistribution and the extent of polarization suppression induced by voltage cycling. Our results suggest that oxygen vacancy motion plays, at most, a secondary role in ferroelectric fatigue of PZT thin films.
Electromagnetic conic sections
Authors: Dray Tevian , Manogue Corinne A.
Published: October 2002

Certain orthogonal coordinate systems naturally correspond to basis vectors which are both curl-free and divergence-free, and hence solve Maxwell’s equations. After first comparing several different traditional approaches to computing div, grad, and curl in curvilinear coordinates, we present a new approach, based on these “electromagnetic” basis vectors, which combines geometry and physics. Not only is our approach tied to a physical interpretation in terms of the electromagnetic field, it is also a useful way to remember the formulas themselves. We give several important examples of coordinate systems in which this approach is valid, in each case discussing the electromagnetic interpretation of the basis. We also give a general condition for when an electromagnetic interpretation is possible.