bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleofection Is an Efficient Nonviral Transfection Technique for Human Bone Marrow–Derived Mesenchymal Stem Cells
Authors: Aluigi Michela , Fogli Miriam , Curti Antonio , Isidori Alessandro , Gruppioni Elisa , Chiodoni Claudia , Colombo Mario P. , Versura Piera , D'Errico-Grigioni Antonia , Ferri Elisa , Baccarani Michele , Lemoli Roberto M.
Published: August 2005

Viral-based techniques are the most efficient systems to deliver DNA into stem cells because they show high gene transduction and transgene expression in many cellular models. However, the use of viral vectors has several disadvantages mainly involving safety risks. Conversely, nonviral methods are rather inefficient for most primary cells. The Nucleofector technology, a new nonviral electroporation-based gene transfer technique, has proved to be an efficient tool for transfecting hard-to-transfect cell lines and primary cells. However, little is known about the capacity of this technique to transfect adult stem cells. In this study, we applied the Nucleofector technology to engineer human bone marrow– derived mesenchymal stem cells (hMSCs). Using a green fluorescent protein reporter vector, we demonstrated a high transgene expression level using U-23 and C-17 pulsing programs: 73.7% ± 2.9% and 42.5% ± 3.4%, respectively. Cell recoveries and viabilities were 38.7% ± 2.9%, 44.5% ± 3.9% and 91.4% ± 1.3%, 94.31% ± 0.9% for U-23 and C-17, respectively. Overall, the transfection efficiencies were 27.4% ± 2.9% (U-23) and 16.6% ± 1.4% (C-17) compared with 3.6% ± 2.4% and 5.4% ± 3.4% of other nonviral transfection systems, such as FUGENE6 and DOTAP, respectively (p < .005 for all comparisons). Nucleofection did not affect the immunophenotype of hM-SCs, their normal differentiation potential, or ability to inhibit T-cell alloreactivity. Moreover, the interleukin-12 gene could be successfully transfected into hMSCs, and the immunomodulatory cytokine was produced in great amount for at least 3 weeks without impairment of its biological activity. In conclusion, nucleofection is an efficient nonviral transfection technique for hMSCs, which then may be used as cellular vehicles for the delivery of biological agents.
Knowledge construction as contested terrain: Adult learning through artistic expression
Authors: Lawrence Randee Lipson
Published: August 2005

Traditional forms of teaching and learning based on textual forms of representation and rational thought may limit how we perceive our world. Artistic forms of expression and their implications for adult education are discussed.
Design and testing of a control system for reverse‐flow catalytic afterburners
Authors: Hevia Miguel A. G. , Ordóñez Salvador , Díez Fernando V. , Fissore Davide , Barresi Antonello A.
Published: August 2005

The design and testing of a control system for reverse‐flow catalytic afterburners based on a two‐variable bifurcation map is focused on. The combustion of lean methane–air mixtures is considered as the test reaction and a bench‐scale apparatus, with a special temperature‐control system based on dynamic compensation of the thermal losses to achieve adiabatic operation, is used for validation purposes. The aim of the control system is to avoid both catalyst overheating and reaction extinction when the adiabatic temperature increases and the flow rate of the feed changes. Stability maps of the reactor are obtained by means of numerical simulations, showing the values of the operating parameters (switching time), which allows fulfillment of the operating constraints (catalyst maximum temperature and methane conversion) when the inlet concentration and flow rate change. This system was realized and tested experimentally, mainly for inlet concentration changes, proving to be effective in all cases investigated. © 2005 American Institute of Chemical Engineers AIChE J, 2005
Missense mutations in N‐acetylglucosamine‐1‐phosphotransferase α/β subunit gene in a patient with mucolipidosis III and a mild clinical phenotype
Authors: Tiede Stephan , Muschol Nicole , Reutter Gert , Cantz Michael , Ullrich Kurt , Braulke Thomas
Published: August 2005

Mucolipidosis type III (ML III, pseudo‐Hurler polydystrophy), an autosomal recessive inherited disorder of lysosomal enzyme targeting is due to a defective N‐acetylglucosamine 1‐phosphotransferase (phosphotransferase) activity and leads to the impaired formation of mannose 6‐phosphate markers in soluble lysosomal enzymes followed by their increased excretion into the serum. Mutations in the phosphotransferase γ subunit gene (GNPTAG) have been reported to be responsible for ML III. Here we report on a 14‐year‐old adolescent with a mild clinical phenotype of ML III. He presented with progressive joint stiffness and swelling. Urinary oligosaccharide and mucopolysaccharide excretion was normal. Lysosomal enzyme activities were significantly elevated in the serum and decreased in cultured fibroblasts. Impaired trafficking of the lysosomal protease cathepsin D (CtsD) was confirmed by metabolic labeling of the patient's fibroblasts. Neither mutations in the GNPTAG gene nor alterations in the GNPTAG mRNA level were detected whereas the steady state concentration of the 97 kDa GNPTAG dimer was reduced. Most importantly, the patient is homozygous for a pathogenic nucleotide substitution and a polymorphism in the phosphotransferase α/β subunit gene (GNPTA). The data indicate that defects in genes other than GNPTAG can be linked to ML III contributing to the variability of the phenotype. © 2005 Wiley‐Liss, Inc.
Michels syndrome, Carnevale syndrome, OSA syndrome, and Malpuech syndrome: Variable expression of a single disorder (3MC syndrome)?
Authors: Titomanlio Luigi , Bennaceur Selim , Bremond‐Gignac Dominique , Baumann Clarisse , Dupuy Olivier , Verloes Alain
Published: August 2005

We report on a 3‐year‐old girl with Michels syndrome, a rare condition characterized by craniosynostosis, blepharophimosis, ptosis, epicanthus inversus, cleft lip/palate, abnormal supra‐umbilical abdominal wall, and mental deficiency. The phenotypic findings are compared with the six previously reported Michels cases, and with patients referred to as Carnevale, OSA, and Malpuech syndromes. Michels syndrome is characterized by cleft lip and palate, anterior chamber anomalies, blepharophimosis, epicanthus inversus, and craniosynostosis. Carnevale syndrome shows hypertelorism, downslanting palpebral fissures, ptosis, strabismus synophrys, large and fleshy ears, and lozenge‐shaped diastasis around the umbilicus. OSA syndrome resembles Carnevale, with humeroradial synostoses, and spinal anomalies as extra features. Malpuech syndrome shows IUGR, hypertelorism, cleft lip and palate, micropenis, hypospadias, renal anomalies, and caudal appendage. All are autosomal recessive. Despite the presence of apparently distinctive key features, it appears that these four entities share multiple similarities in the facial Gestalt and the pattern of MCA. Those similarities lead us to postulate that they belong to the same spectrum, which could be referred to as “3MC syndrome” (Malpuech‐Michels‐Mingarelli‐Carnevale syndrome). © 2005 Wiley‐Liss, Inc.
Acrofacial dysostosis (AFD) with preaxial limb hypoplasia (Nager AFD) and club foot diagnosed in a fetus from 1812 in the anatomical collections at the University of Halle, Germany
Authors: Göbbel Luminita , Schultka Rüdiger , Klunker Rudyard , Stock Karsten , Wand Dorothee , Olsson Lennart , Gerlach Antje , Tönnies Holger
Published: August 2005

The Anatomical Collections of the Department of Anatomy and Cell Biology at the University of Halle, Germany, comprise more than 8,000 specimens, about 600 of them congenital anomalies. The collection of abnormal human and animal specimens began with the private collections of Johann Friedrich Meckel the Elder (1724–1774), his son Philipp Friedrich Theodor Meckel (1755–1803), and his grandson Johann Friedrich Meckel the Younger (1781–1833). Meckel the Younger founded the science of developmental pathology in Germany. Radiographical techniques, computer tomographic methods (CT), magnetic resonance imaging (MRI), and molecular cytogenetic techniques, for example, comparative genomic hybridization (CGH) were used to diagnose abnormal human fetuses in the Meckel Collection. On examination of one of the human fetuses, originally described by JF Meckel the Younger in 1812 or earlier, we found striking clinical manifestations including mandibulofacial defects and preaxially malformed limbs. With respect to external findings, we propose that the condition is acrofacial dysostosis (AFD) with preaxial limb hypoplasia (Nager AFD) in combination with club foot, tibial torsion, and single umbilical artery. We used genetic analyses to test whether the observed limb malformations could be caused by aneuploidy. CGH‐ratio profiles of all chromosomes were apparently normal. It is likely that Meckel's specimen is the earliest known fetus with Nager AFD. © 2005 Wiley‐Liss, Inc.
Oxidative Electrochemical Switching in Dithienylcyclopentenes, Part 1: Effect of Electronic Perturbation on the Efficiency and Direction of Molecular Switching
Authors: Browne Wesley R. , de Jong Jaap J. D. , Kudernac Tibor , Walko Martin , Lucas Linda N. , Uchida Kingo , van Esch Jan H. , Feringa Ben L.
Published: August 2005

The electro‐ and spectroelectrochemical properties of dithienylhexahydro‐ and dithienyhexafluorocyclopentenes are reported. The large effect of variation in the central cyclopentene moieties on the redox properties of the dithienylcyclopentenes is in striking contrast to the minor effect on their photochemical properties. The electronic properties of the oxidised compounds in the +1 and +2 oxidation state are reported, and the possibility of electrochemical cyclisation and cycloreversion were explored by UV/Vis spectroelectrochemistry. The efficiency of electrochemical switching is found to be dependent both on the central cyclopentene unit and on the nature of the substituents at C5 of the thienyl rings. For the hexahydrocyclopentene‐based compounds oxidative ring closure of the ring‐open form is observed, while for the hexafluorocyclopentene‐based compounds oxidative ring opening of the ring‐closed form is observed. However, the introduction of electroactive groups such as methoxyphenyl allows oxidative ring closure to occur in the hexafluoro compounds. The effect of electrolyte, solvent and temperature on the spectroelectrochemical properties were examined, and the switching process was found to be sensitive to the donor properties of the solvent/electrolyte system employed. In addition, thermally activated reversible isomerisation of the dicationic closed form was observed. The driving force for electrochemical ring opening and closure appears to be dependent on the relative stabilisation of the dicationic ring‐open and ring‐closed states. This study provides insight into the factors which determine the direction of cyclisation.
Stereoselectivity of the reduced folate carrier in Caco‐2 cells
Authors: Narawa Tomoya , Shimizu Rikako , Takano Shuhei , Tsuda Yasuyuki , Ono Kiyoko , Yamada Hideo , Itoh Tomoo
Published: August 2005

Stereoselectivity of the human reduced folate carrier (RFC1) was examined in Caco‐2 cells using methotrexate (l‐amethopterin or l‐MTX) and its antipode (d‐amethopterin or d‐MTX) as model substrates. The initial uptake rate of folic acid (FA) was concentration dependent, with a Km value of approximately 0.6 μM. The Eadie–Hofstee plot of the RFC1‐mediated FA uptake revealed a single component for FA uptake into Caco‐2 cells, demonstrating that only RFC1 is involved in FA uptake. l‐MTX inhibited FA uptake in a competitive manner with a Ki value of approximately 2 μM, similar to the Km value of l‐MTX. d‐MTX also competitively inhibited FA uptake with a Ki value being approximately 120 μM, indicating that the affinity of d‐MTX is ca. 60‐fold less than that of l‐MTX. The stereoselectivity of human RFC1 observed in the present study was consistent not only with the stereoselectivity of rabbit RFC1 observed in rabbit intestinal brush border membrane vesicles but also with the reported differences in oral absorption of amethopterin enantiomers in humans. © 2005 Wiley‐Liss, Inc. Chirality 17:444–449, 2005.
Chiral separation and CD characterisation of enantiomeric cyclotriphosphazene derivatives
Authors: Bui Tam T.T. , Coles Simon J. , Davies David B. , Drake Alex F. , Eaton Robert J. , Hursthouse Michael B. , Kılıç Adem , Shaw Robert A. , Yeşilot Serkan
Published: August 2005

The gem‐disubstituted cyclotriphosphazene 1 reacted with piperazine (pip) to give the piperazine‐bridged derivative 2, which is expected to exist in meso and racemic forms because the two PCl (pip) groups are stereogenic. The proton‐decoupled 31P NMR spectrum of 2 gave rise to two similar sets of ABX signals in a 1:1 ratio, consistent with formation of diastereoisomers. The meso and racemic forms of compound 2 were separated by column chromatography on silica gel and characterised by elemental analysis, mass spectrometry, 31P NMR spectroscopy, and X‐ray crystallography. Using HPLC with a chiral stationary phase, the racemic form of compound 2 was further separated into enantiomers, which were characterised by circular dichroism (CD) spectroscopy. This is the first report of the separation of enantiomers in the field of cyclophosphazene chemistry and hence the first CD spectra of derivatives in which the cyclophosphazene ring is at the chiral centre. © 2005 Wiley‐Liss, Inc. Chirality 17:438–443, 2005.
Conformational Control of Calix[6]arenes Through Multiple Bridges
Authors: Galán Hitos , de Mendoza Javier , Prados Pilar
Published: August 2005

The synthesis of the A,D‐m‐xylylene‐bridged B,C,E,F‐tetra‐O‐alkylcalix[6]arenes 1b–c and the A,D‐B,C;E,F‐triply bridged calix[6]arenes 2a–c is described. The cone conformation of the new bridged calix[6]arenes has been established by a full set of 1D/2D 1H and 13C NMR techniques. These compounds are substantially more rigid than calix[6]arene analogues with an A,D‐p‐xylylene bridge, and the resulting cavities are better defined. Molecular mechanics optimization of triply bridged calix[6]arenes 2b and 2c resulted in structures fully consistent with the NMR spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis of High Molecular Weight Amphiphilic Polyphenylenes by Suzuki Polycondensation
Authors: Kandre Ramchandra M. , Kutzner Fabian , Schlaad Helmut , Schlüter A. Dieter
Published: August 2005

Summary: Four different 1,4‐ and 1,3‐dibromobenzenes carrying nonpolar dodecyloxy and linear as well as branched polar oligo(ethylene glycol) side chains were subjected to Suzuki polycondensation (SPC) with benzene‐1,4‐bisboronic acid ester to produce high‐molecular‐weight amphiphilic polyphenylenes, three of which are all‐para and one is meta linked. Molecular weights were determined by size exclusion chromatography with conventional polystyrene calibration and, for two selected samples, with universal calibration. Polymerization under SPC conditions of one of the 1,4‐dibromo monomers is compared to that of the direct 1,4‐diiodo analog.

Polyphenylenes prepared in this study.

image

Polyphenylenes prepared in this study.
The cytoskeleton‐dependent localization of cdc2/cyclin B in blastomere cortex during Xenopus embryonic cell cycle
Authors: Nakamura Norihiko , Tokumoto Toshinobu , Ueno Shuichi , Iwao Yasuhiro
Published: August 2005

In the early development of the frog, Xenopus laevis, blastomeres undergo synchronous divisions at about the 12th cell cycle, followed by asynchronous divisions, which is referred to as mid‐blastula transition (MBT). We investigated the distribution of several regulating factors for cell cycles around MBT using immunocytochemistry and confocal fluorescence microscopy. At the 8th cell cycle, most of the cdc2/cyclin B was localized in the cortical cytoplasm throughout the cell cycle, in the centrosomes and the nucleus at interphase and prometaphase, and in the spindles at metaphase and anaphase. Cdc2 was also localized in the chromatins at metaphase and anaphase. Cyclin B1 mRNA was localized in the periphery of the nucleus, but not in the cell cortex. At the 13th cell cycle, the amount of cdc2/cyclin B in the cortical cytoplasm decreased, and the inactive form of cdc2, phosphorylated at tyrosine 15, appeared in the nucleus and the centrosomes at interphase, indicating that the regulation of cdc2 by phosphorylation occurs around MBT. When the blastomeres were treated with nocodazole or latrunculin A at the 8th cell cycle, the amount of cortical cdc2 decreased, but that of cyclin B did not change. The cortical localization of cdc2 is dependent upon both microtubules and microfilaments. Most of the cdc27 was localized in the centrosomes, and in the spindle poles, but no significant difference was observed between the 8th and the 13th cell cycles. It is possible that the cortical MPF activity is regulated by the differential localization between cdc2 and cyclin B. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Sensitivity analysis of partial differential equations: A case for functional sensitivity
Authors: Kabala Z. J. , Milly P. C. D.
Published: August 2005

Sensitivity analysis allows for analyzing the effects of parameter uncertainty. For functional parameters, the sensitivity of the system is described by the functional derivatives of the output variables with respect to the parameters. Approximation of each of the functional parameters by a finite number of scalars (via the finite element representation) allows one to use elementary sensitivity analysis. The functional sensitivities are easily approximated from elementary sensitivities and, being objective quantities, they allow one to evaluate the numerical quality of sensitivities. The grid density necessary for computing functional sensitivities may differ significantly from the grid required for the numerical solution of the governing equation.
Asymptotic factorization of evolution equations which involve linear operators
Authors: Cooke Charlie H. , McMorran Andrew G.
Published: August 2005

Operator splitting for evolution equations which involve linear operators is investigated. A systematic method for identifying multifactor fractional‐step operator splittings is proposed. The classical second‐order accurate splittings of Strang readily emerge, as well as various third‐order splittings of nonstandard type. Factorizations possessing mixed positive‐negative fractional steps are discovered, as well as bizarre splittings whose factors include complex fractional steps. It is found that no higher‐order accurate splitting which employs all positive fractional steps and which possesses less than nine operator factors can exist. For the linear case this implies second‐order accurate splittings are optimal, as a further increase of one power in accuracy essentially requires a three‐fold increase in work. This estimate slightly improves, for cases where the nonstandard splittings can be employed. Some numerical experiments which illustrate the theory are provided.
Total dependence of the cerebral circulation on the right vertebral artery in Takayasu's disease—A case report
Authors: Elewaut Dirk S. , Duprez Daniel A. , De Buyzere Marc L. , Kunnen Marc F. , Clement Denis L.
Published: August 2005

A twenty-four-year-old woman with Takayasu's disease was admitted in June 1992 to the hospital because of amaurosis fugax. There were neither a history of stroke nor other neurologic signs. For a long time the patient had suffered from extreme fatigue and claudication of the upper limbs. In 1988 arteriography revealed total occlusion of both subclavian arteries and a severe filiform stenosis of the left common carotid artery. The disease appeared to be stable between 1988 and 1992 without obvious signs of inflammation. At present arteriography additionally reveals total occlusion of both common carotid arteries and the left vertebral artery. Only the right vertebral artery is patent, although presenting clear stenosis at its origin. A computed tomographic scan of the brain appears normal.

The progression of the disease in the absence of inflammatory episodes since 1988 and the total dependence of the cerebral arterial circulation on the right vertebral artery are the hallmarks of this very rare case of Takayasu's disease.
Plant–animal interactions in seagrass beds: ongoing and future challenges for understanding population and community dynamics
Authors: Nakaoka Masahiro
Published: August 2005

Seagrass beds are some of the most productive parts of coastal ecosystems, hosting a wide variety of associated fauna. This paper reviews recent studies of animal–plant interactions in seagrass beds, focusing particularly on studies conducted in Japan and Thailand. Although the positive effect of seagrass habitat structure on animals has been widely acknowledged, the magnitude of this effect varies greatly among studies. A comparative study on epifaunal communities and a manipulative experiment using an infaunal bivalve revealed that behavioral and life‐history traits of component species and their interactions influence the observed variation. Some recent studies have challenged the previously accepted view that direct herbivory on seagrasses is rare, and has a minor effect on the seagrass community. A series of studies of dugong herbivory revealed that the marine mammal has great impacts not only on seagrass productivity but also on the infaunal community. Furthermore, it has been found that seed predators have a negative influence on seed production and the subsequent recruitment of seagrass. Recent studies have also demonstrated significant effects of fine‐scale landscape patterns in seagrass vegetation on productivity, species interactions and community structure in seagrass beds. Future research integrating new concepts and theories in ecology, such as metapopulation and hierarchy theories, with new research tools, such as molecular‐genetic analyses and remote‐sensing techniques, may aid in developing a more comprehensive understanding of population and community dynamics in seagrass beds.
Fear of pain, not pain catastrophizing, predicts acute pain intensity, but neither factor predicts tolerance or blood pressure reactivity: An experimental investigation in pain‐free individuals
Authors: George Steven Z. , Dannecker Erin A. , Robinson Michael E.
Published: August 2005

Previous studies of the Fear‐Avoidance Model of Exaggerated Pain Perception have commonly included patients with chronic low back pain, making it difficult to determine which psychological factors led to the development of an “exaggerated pain perception”. This study investigated the validity of the Fear‐Avoidance Model of Exaggerated Pain Perception by considering the influence of fear of pain and pain catastrophizing on acute pain perception, after considering sex and anxiety. Thirty‐two males and 34 females completed the State‐Trait Anxiety Inventory, the Fear of Pain Questionnaire, and the Coping Strategies Questionnaire. Subjects underwent a cold pressor procedure and tolerance, pain intensity, and blood pressure reactivity were measured. Sex, anxiety, fear of pain, and pain catastrophizing were simultaneously entered into separate multiple regression models to predict different components of pain perception. Tolerance was not predicted by fear of pain, pain catastrophizing, or anxiety. Pain intensity at threshold and tolerance were significantly predicted by fear of pain, only. Blood pressure reactivity to pain was significantly predicted by anxiety, only. These results suggest that fear of pain may have a stronger influence on acute pain intensity when compared to pain catastrophizing, while neither of the factors predicted tolerance or blood pressure reactivity.
Electroporation of the heart
Authors: Nikolski Vladimir P. , Efimov Igor R.
Published: August 2005

Defibrillation shocks are commonly used to terminate life-threatening arrhythmias. According to the excitation theory of defibrillation, such shocks are aimed at depolarizing the membranes of most cardiac cells resulting in resynchronization of electrical activity in the heart. If shock-induced changes in transmembrane potential are large enough, they can cause transient tissue damage due to electroporation. In this review evidence is presented that (a) electroporation of the heart tissue can occur during clinically relevant intensities of the external electrical field, and (b) electroporation can affect the outcome of defibrillation therapy; being both pro- and anti-arrhythmic.
Climate, zooplankton, and pelagic fish growth in the central Baltic Sea
Authors: Möllmann Christian , Kornilovs Georgs , Fetter Marina , Köster Friedrich W.
Published: August 2005

Oceanographic conditions in the brackish central Baltic Sea are strongly linked to atmospheric forcing and the unusual period of persistently strong westerlies that, since the late 1980s, have resulted in an increase in average water temperatures and decreasing salinity. These changes in temperature and salinity resulted in a change in the dominance of the mesozooplankton community from Pseudocalanus sp. to Temora longicornis and Acartia spp. Similar to the copepod community, the central Baltic fish community shifted from cod (Gadus morhua), dominant during the 1980s, to sprat (Sprattus sprattus), dominant during the 1990s. Further, the commercially important pelagic fish species herring (Clupea harengus) and sprat exhibited reductions in growth. Using Principal Component and Correlation Analyses we investigated the temporal variability in the importance of the food supply as well as competition on condition of central Baltic pelagic fish species. Our results indicate that herring condition results from a combined effect of changes in the food environment and increased competition with sprat, while sprat condition appeared to be primarily determined by intra-specific competition.
Neonatal cerebral hypoxia‐ischemia: involvement of FAK‐dependent pathway
Authors: Zalewska Teresa , Makarewicz Dorota , Janik Bernardetta , Ziemka‐Nałęcz Małgorzata
Published: August 2005

Focal adhesion kinase (FAK) is a non‐receptor tyrosine kinase thought to play a major role in transducing extracellular matrix (ECM)‐derived survival signals into cells. Thus, modulation of FAK activity may affect the linkage between ECM and signaling cascade to which it is connected and may participate in a variety of pathological settings. In the present study, we investigated the effect of neonatal cerebral hypoxia‐ischemia (HI) on levels and tyrosine phosphorylation of focal adhesion kinase and the interaction of this enzyme with Src protein tyrosine kinase and adapter protein p130Cas, involved in FAK‐mediated signaling pathway. The total amount of focal adhesion kinase as well as its phosphorylated form declined substantially to about 50% of the control between 24 and 48 h after the insult. Concomitantly a decreased association of FAK with its investigated molecular partners, Src kinase and p130Cas protein has been observed. This early response to brain hypoxia‐ischemia was attenuated during prolonged recovery with almost complete return to control values at 7 days. These data are indicative of an involvement of FAK‐dependent signaling pathway in the evolution of HI‐induced neuronal degeneration.
Methionine alters Na+,K+‐ATPase activity, lipid peroxidation and nonenzymatic antioxidant defenses in rat hippocampus
Authors: Stefanello Francieli M. , Chiarani Fábria , Kurek Andréa G. , Wannmacher Clovis M.D. , Wajner Moacir , Wyse Angela T.S.
Published: August 2005

In the present study we investigated the effect of methionine exposure of hippocampus homogenates on Na+,K+‐ATPase activity from synaptic plasma membrane of rats. Results showed that methionine significantly decreased this enzyme activity. We also evaluated the effect of incubating glutathione (GSH) and trolox (α‐tocopherol) alone or combined with methionine on Na+,K+‐ATPase activity. The tested antioxidants per se did not alter the enzymatic activity, but prevented the inhibitory action of methionine on Na+,K+‐ATPase activity, indicating that Met inhibitory effect was probably mediated by free radical formation. Besides, we tested the in vitro effect of methionine on some parameters of oxidative stress, namely chemiluminescence, thiobarbituric acid reactive substances (TBARS), total radical‐trapping antioxidant potential (TRAP), as well as on the antioxidant enzyme activities catalase, glutathione peroxidase and superoxide dismutase in rat hippocampus. We observed that methionine significantly increased chemiluminescence and TBARS, decreased TRAP, but did not change the activity of the antioxidant enzymes. These findings suggest that reduction of Na+,K+‐ATPase activity and induction of oxidative stress may be involved in the brain damage observed in human hypermethioninemia.
Surgical Efficacy of Carpal Tunnel Release for Carpal Tunnel Syndrome in Acromegaly: Report of Four Patients
Authors: IWASAKI N. , MASUKO T. , ISHIKAWA J. , MINAMI A.
Published: August 2005

Although carpal tunnel syndrome is frequent in acromegaly, few acromegalics will be encountered by most hand surgeons. This paper considers the treatment of four cases of acromegaly in whom carpal tunnel syndrome arose, to discuss aspects of management of carpal tunnel syndrome in this patient group.
Single-molecule pump-probe experiments reveal variations in ultrafast energy redistribution
Authors: van Dijk E. M. H. P. , Hernando J. , García-Parajó M. F. , van Hulst N. F.
Published: August 2005

Single-molecule pump probe (SM2P) is a novel, fluorescence-based technique that allows the study of ultrafast processes on the single-molecule level. Exploiting SM2P we have observed large variations (from 1ps to below 100fs) in the energy redistribution times of chemically identical molecules in the same sample. Embedding the molecules in a different matrix or changing the excitation wavelength does not lead to significant changes in the average redistribution time. However, chemically different molecules exhibit different characteristic redistribution times. We therefore conclude that the process measured with the SM2P technique is dominated by intramolecular energy redistribution and not intermolecular transfer to the surrounding matrix. The matrix though is responsible for inducing conformational changes in the molecule, which affect the coupling between electronic and vibrational modes. These conformational changes are the main origin of the observed broad distribution of redistribution times.
Epitaxial growth of a nanoscale, vertically faceted, one-dimensional, high-aspect ratio grating in III-V materials for integrated photonics
Authors: Lee S. C. , Dawson L. R. , Brueck S. R. J.
Published: August 2005

Homoepitaxial selective growth of a GaAs nanoscale, high-aspect ratio, one-dimensional (1D) grating with vertical facets is reported. For a pattern direction along [110], the kinetics of faceting in selective molecular-beam epitaxy (MBE) induce (11¯0)-type facets vertical to a GaAs(001) substrate near the boundary between an SiO2 mask and an open substrate area. On a 1.25-μm period, 1D stripe, SiO2-patterned GaAs(001) substrate with an opening width of ∼300nm, vertical faceting results in a grating structure consisting of 2.8-μm-high, 820-nm-wide features. Kinetics of faceting in selective MBE is explained as a result of the minimization of total surface energy.
Enhanced collisionless heating in a nonuniform plasma at the bounce resonance condition
Authors: Polomarov Oleg V. , Theodosiou Constantine E. , Kaganovich Igor D.
Published: August 2005

The importance of accounting for a nonuniform density profile for modeling of collisionless electron heating in a bounded low-pressure plasma is demonstrated. A drastic enhancement of the power transfer into an inductive plasma under the condition of a bounce resonance is observed if the nonuniformity of the plasma density profile is accounted for. This enhanced plasma heating is attributed to the increase of the number of resonant electrons, for which the bounce frequency of electrons confined inside the plasma potential is equal to the rf field frequency.
Hyperpolarizabilities for the one-dimensional infinite single-electron periodic systems. I. Analytical solutions under dipole-dipole correlations
Authors: Jiang Shidong , Xu Minzhong
Published: August 2005

The analytical solutions for the general-four-wave-mixing hyperpolarizabilities χ(3)[−(ω1+ω2+ω3);ω1,ω2,ω3] on infinite chains under both Su–Shrieffer–Heeger and Takayama–Lin–Liu–Maki models of trans-polyacetylene are obtained through the scheme of dipole-dipole correlation. Analytical expressions of dc Kerr effect χ(3)(−ω;0,0,ω), dc-induced second-harmonic generation χ(3)(−2ω;0,ω,ω), optical Kerr effect χ(3)(−ω;ω,−ω,ω), and dc electric-field-induced optical rectification χ(3)(0;ω,−ω,0) are derived. By including or excluding ∇k terms in the calculations, comparisons show that the intraband contributions dominate the hyperpolarizabilities if they are included. ∇k term or intraband transition leads to the break of the overall permutation symmetry in χ(3) even for the low-frequency and nonresonant regions. Hence it breaks the Kleinman [Phys. Rev. 126, 1977 (1962)] symmetry that is directly based on the overall permutation symmetry. Our calculations provide a clear understanding of the Kleinman symmetry breaks that are widely observed in many experiments. We also suggest a feasible experiment on χ(3) to test the validity of overall permutation symmetry and our theoretical prediction. Finally, our calculations show the following trends for the various third-order nonlinear optical processes in the low-frequency and nonresonant region: χnonres(3)(−3ω;ω,ω,ω)>χnonres(3)(−2ω;0,ω,ω)>χnonres(3)(−ω;ω,−ω,ω)>χnonres(3)(−ω;0,0,ω)⩾χnonres(3)(0;ω,−ω,0), and in the resonant region: χres(3)(−ω;0,0,ω)>χres(3)(−ω;ω,−ω,ω)>χres(3)(−2ω;0,ω,ω)>χres(3)(0;ω,−ω,0)>χres(3)(−3ω;ω,ω,ω).
Diffusion of charged fluids in charged porous matrices
Authors: Dominguez Hector , Rivera Margarita
Published: August 2005

Computer simulations to study the diffusion of charged fluids in charged porous matrices were performed. The matrix was prepared using a template, i.e., it was simulated from a neutral binary mixture of charged particles where one of the components served as the template and the other as the matrix. The final porous matrix was obtained by removing template particles from the mixture. Then, the diffusion of a charged fluid immersed in the porous matrix was studied showing that in some cases, it increased as the fluid density increased. The results can be explained in terms of possible traps created in the matrix which capture mobile particles. Pair correlation functions of the fluid particles were studied and they showed strong structure for trapped particles indicating low motion of such mobile charges.
Effect of high-pressure annealing on magnetoresistance in manganese perovskites
Authors: Huang Y. H. , Karppinen M. , Yamauchi H. , Goodenough J. B.
Published: August 2005

Through high-pressure (HP) annealing, a large enhancement of the magnetoresistance (MR) has been achieved for polycrystalline La0.7Sr0.3MnO3 samples over a wide range of temperature at low applied magnetic fields. Moreover, the HP-annealed samples exhibit much lower resistivity and higher metal-insulator transition temperatures. Interestingly, the low-field MR (LFMR*) values at 5K of such HP-annealed samples are found to reach as high as 45%, significantly exceeding a theoretical upper limit of 33% based on the second-order tunneling through interfacial spin sites for the polycrystalline manganese oxides. We attribute the enhanced LFMR* to the effect of HP annealing that makes the grain boundary thinner and thus allows a large fraction of eg electrons tunnel directly across the grain boundary rather than by a two-step hop process.
Resistive switching mechanism of TiO2 thin films grown by atomic-layer deposition
Authors: Choi B. J. , Jeong D. S. , Kim S. K. , Rohde C. , Choi S. , Oh J. H. , Kim H. J. , Hwang C. S. , Szot K. , Waser R. , Reichenberg B. , Tiedke S.
Published: August 2005

The resistive switching mechanism of 20- to 57-nm-thick TiO2 thin films grown by atomic-layer deposition was studied by current-voltage measurements and conductive atomic force microscopy. Electric pulse-induced resistance switching was repetitively (> a few hundred times) observed with a resistance ratio ⪢102. Both the low- and high-resistance states showed linear log current versus log voltage graphs with a slope of 1 in the low-voltage region where switching did not occur. The thermal stability of both conduction states was also studied. Atomic force microscopy studies under atmosphere and high-vacuum conditions showed that resistance switching is closely related to the formation and elimination of conducting spots. The conducting spots of the low-resistance state have a few tens times higher conductivity than those of the high-resistance state and their density is also a few tens times higher which results in a ∼103 times larger overall conductivity. An interesting finding was that the area where the conducting spots do not exist shows a few times different resistance between the low- and high-resistance state films. It is believed that this resistance change is due to the difference in point defect density that was generated by the applied bias field. The point defects possibly align to form tiny conducting filaments in the high-resistance state and these tiny conducting filaments gather together to form stronger and more conducting filaments during the transition to the low-resistance state.
Two-fluid magnetic island dynamics in slab geometry: Determination of the island phase velocity
Authors: Fitzpatrick R. , Watson P. G. , Waelbroeck F. L.
Published: August 2005

The physics which determines the phase-velocity of a comparatively wide, isolated, magnetic island, formed as a result of a nonlinear tearing instability in a magnetic confinement device relying on the existence of nested magnetic flux surfaces, is investigated using a two-fluid model in slab geometry. It is found that the phase velocity is fixed by momentum transport across the magnetic flux surfaces in the region immediately surrounding the magnetic separatrix. Analytic predictions for the phase velocity are obtained, and are successfully benchmarked against the results of two-dimensional, drift-magnetohydrodynamical simulations.
Direct formation of Na3AlH6 by mechanical milling NaH∕Al with TiF3
Authors: Wang P. , Kang X. D. , Cheng H. M.
Published: August 2005

Na 3 Al H 6 can be directly formed by mechanical milling NaH∕Al with TiF3 under hydrogen atmosphere. The hydrogenation fraction of NaH increases with increasing the milling time, and reaches up to 0.61 after 20h milling. Thus-formed Na3AlH6 exhibits unexpected polymorphic transformation and decomposition behaviors. This, together with the unusual hydrogen storage performance of the mechanically prepared materials, provides us a suggestive perspective to probe the favorable modification of the thermodynamics of Na3AlH6 and nature of active Ti-species in Ti-doped NaAlH4.
Design and construction of a mechanically simple, interdigitated-wire ion gate
Authors: Szumlas Andrew W. , Rogers Duane A. , Hieftje Gary M.
Published: August 2005

This note describes the design of a simple, wire-array ion gate that is easy to create and machine. The gate consists of two separate wires that can be pulsed differentially to either neutralize ions or deflect the path of an ion beam. Unlike previous designs, the gate described herein consists of only a single piece: an insulator through which two wires are woven to create an interdigitated array. The wires are then terminated at both ends, where electrical connections to external voltage sources can be made. Once constructed, the gate has a 1 mm grid spacing and takes about 3–4 h to complete after the initial support is machined. A gate constructed with this design has been successfully installed in an ion-mobility spectrometer, and its performance compares favorably to that of a previously configured gate system.
Accurate measurements of high pressure resistivity in a diamond anvil cell
Authors: Gao Chunxiao , Han Yonghao , Ma Yanzhang , White Allen , Liu Hongwu , Luo Jifeng , Li Ming , He Chunyuan , Hao Aimin , Huang Xiaowei , Pan Yuewu , Zou Guangtian
Published: August 2005

A new technique incorporating a diamond anvil cell with photolithographic and film deposition techniques has been developed for electrical resistivity measurement under high pressure. Molybdenum was sputtered onto a diamond anvil facet and patterned to the desired microcircuit. A sputtered Al2O3 (alumina) layer was then fabricated onto the Mo-coated layer to insulate the thin-film electrodes from the metallic gasket and to protect the electrodes against plastic deformation under high pressure conditions. For better insulation, Al2O3 was also sputtered onto the metallic gasket. The regular shape of the microcircuit makes it convenient to perform an electric current field analysis, hence, accurate resistivity data can be obtained from the measurement. We performed the measurement of nanocrystalline ZnS to 36 GPa and determined its reversibility and phase transition hysteresis.
Turbulent stress invariant analysis: Clarification of existing terminology
Authors: Simonsen A. J. , Krogstad P.-Å.
Published: August 2005

As a means of studying the structure of the turbulence, the time mean invariants, defined according to the theory of Lumley [“Computational modelling turbulent flows,” Adv. Appl. Mech. 18, 123 (1978)] has proven to be a useful and popular tool. According to the theory there is a domain, known as the anisotropy invariant map, within which all realizable Reynolds’s stress invariants must lie. The borders of this domain describe different states of the turbulent stress tensor. It has been found that there is some confusion in the terminology used when describing these states. The confusion is related to whether the notation is used to describe the shape of the stress tensor or the eddies of the turbulence. Choi and Lumley [“The return of isotropy of homogeneous turbulence,” J. Fluid Mech. 436, 59 (2001)] noted the same controversy in terminology, but since the confusion is still found to exist, it was thought timely to describe the fundamental relationships which relate the shape of the stress tensor and its invariants.
Rayleigh–Taylor turbulent mixing of immiscible, miscible and stratified fluids
Authors: Abarzhi S. I. , Gorobets A. , Sreenivasan K. R.
Published: August 2005

We propose a simple empirical model to describe the Rayleigh–Taylor (RT) turbulent mixing of immiscible, miscible and stratified fluids. For immiscible fluids, the rate of momentum loss is an invariant of the flow, whereas the energy dissipation rate increases linearly with time. Turbulent diffusion, accounted for through temperature fluctuations, does not terminate mixing but slows it down significantly. A stratified density distribution can stabilize RT mixing.
Design and performance of a microsecond time-resolved photo-chemically induced dynamic nuclear polarization add-on for a high-field nuclear magnetic resonance spectrometer
Authors: Kuprov I. , Goez M. , Abbott P. A. , Hore P. J.
Published: August 2005

We describe the design and operation of microsecond time-resolved photo-chemically induced dynamic nuclear polarization hardware, designed to go with a commercial 600 MHz nuclear magnetic resonance (NMR) spectrometer. A frequency-tripled neodymium-doped yttrium/aluminum garnet (Nd:YAG) laser is used as the light source, with a system of mirrors or prisms to route light to the NMR sample from above, removing the need for NMR probe modifications. The experiment has been designed for a shared NMR spectrometer and is straightforward and inexpensive to assemble and operate.
Low-temperature GaN growth on silicon substrates by single gas-source epitaxy and photo-excitation
Authors: Trivedi R. A. , Tolle J. , Chizmeshya A. V. G. , Roucka R. , Ritter Cole , Kouvetakis J. , Tsong I. S. T.
Published: August 2005

We report a unique low-temperature growth method for epitaxial GaN on Si(111) substrates via a ZrB2(0001) buffer layer. The method utilizes the decomposition of a single gas-source precursor (D2GaN3)3 on the substrate surface to form GaN. The film growth process is further promoted by irradiation of ultraviolet light to enhance the growth rate and ordering of the film. The best epitaxial film quality is achieved at a growth temperature of 550°C with a growth rate of 3nm∕min. The films exhibit intense photoluminescence emission at 10K with a single peak at 3.48eV, indicative of band-edge emission for a single-phase hexagonal GaN film. The growth process achieved in this study is compatible with low Si processing temperatures and also enables direct epitaxy of GaN on ZrB2 in contrast to conventional metalorganic chemical vapor deposition based approaches.
Rhodium-oxide-coated indium tin oxide for enhancement of hole injection in organic light emitting diodes
Authors: Kim Soo Young , Baik Jeong Min , Yu Hak Ki , Kim Kwang Young , Tak Yoon-Heung , Lee Jong-Lam
Published: August 2005

The authors report the enhancement of hole injection using an RhOx layer between indium tin oxide anodes and 4,4′-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl in organic light-emitting diodes (OLEDs). The operation voltage of OLEDs at 700cd∕m2 decreased from 13 to 10 V as the Rh layer changed to RhOx by surface treatment using O2 plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased by 0.2 eV as the Rh layer transformed into RhOx. Thus, the hole injection energy barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs.
Quantitative analysis on the effects of AlAs X states on Γ resonance in a GaAs∕AlAs double barrier structure under elevated hydrostatic pressures
Authors: Kim Yongmin , Jung Kyooho , Im Hyunsik , Klipstein P. C. , Grey R. , Hill G.
Published: August 2005

We have investigated Γ-symmetry resonant tunneling in a GaAs∕AlAs “double barrier structure” with 20 Å thick AlAs barriers as a function of hydrostatic pressure. A quantitative analysis based on transfer matrix and self-consistent Schrödinger-Poisson calculations is performed to understand the effects of charge accumulation in each layer on the resonance bias and the resonance peak/valley currents, yielding the value of the longitudinal mass (mz*) at the band edge of 20 Å thick AlAs, mz*=(0.35±0.05)m0.
Preventing local regeneration of glucocorticoids by 11β-hydroxysteroid dehydrogenase type 1 enhances angiogenesis
Authors: Small Gary R. , Hadoke Patrick W. F. , Sharif Isam , Dover Anna R. , Armour Danielle , Kenyon Christopher J. , Gray Gillian A. , Walker Brian R.
Published: August 2005

Angiogenesis restores blood flow to healing tissues, a process that is inhibited by high doses of glucocorticoids. However, the role of endogenous glucocorticoids and the potential for antiglucocorticoid therapy to enhance angiogenesis is unknown. Usingin vitroandin vivomodels of angiogenesis in mice, we examined effects of (i) endogenous glucocorticoids, (ii) blocking endogenous glucocorticoid action with the glucocorticoid receptor antagonist RU38486, and (iii) abolishing local regeneration of glucocorticoids by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1). Glucocorticoids, administered at physiological concentrations, inhibited angiogenesis in anin vitroaortic ring model andin vivoin polyurethane sponges implanted s.c. RU38486-enhanced angiogenesis in s.c. sponges, in healing surgical wounds, and in the myocardium of mice 7 days after myocardial infarction induced by coronary artery ligation. 11βHSD1 knockout mice showed enhanced angiogenesisin vitroandin vivowithin sponges, wounds, and infarcted myocardium. Endogenous glucocorticoids, including those generated locally by 11βHSD1, exert tonic inhibition of angiogenesis. Inhibition of 11βHSD1 in liver and adipose has been advocated to reduce cardiovascular risk in the metabolic syndrome: these data suggest that 11βHSD1 inhibition offers a previously uncharacterized therapeutic approach to improve healing of ischemic or injured tissue.