bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppressive Activity of Fexofenadine Hydrochloride on Thymus- and Activation-Regulated Chemokine Production from Human Peripheral Blood Leukocytes in Response to Antigenic Stimulation in vitro
Authors: Asano Kazuhito , Kanai Ken-ichi , Suzaki Harumi
Published: February 2004

Background: Thymus- and activation-regulated chemokine (TARC) is accepted as being an important molecule in the development and maintenance of allergic diseases. However, there is little information about the influence of antiallergic agents on TARC production after allergen challenge. The aim of this study is to examine the influence of fexofenadine hydrochloride (FEX), an H1-receptor antagonist, on TARC production from human peripheral blood leukocytes (PBL) using an in vitro cell culture technique. Methods: PBL prepared from donors with pollinosis were cultured with either Japanese cedar pollen allergen, Cry j 1, or interleukin (IL)-4 in the presence of various doses of FEX for 6 days. Levels of TARC and the T cell cytokines IL-4 and interferon (IFN)-γ in culture supernatants were examined by ELISA. Results: FEX did not affect PBL proliferation induced by Cry j 1 stimulation, even when 500 ng/ml of the agent, twice the therapeutic blood levels, was added to cell cultures as assessed by measuring 3H-thymidine incorporation into DNA. On the other hand, FEX at 250 ng/ml (but not 125 ng/ml), similar to therapeutic blood levels, significantly inhibited the ability of PBL to produce IL-4 (but not IFN-γ), which was enhanced by Cry j 1 stimulation. FEX at concentrations of more than 250 ng/ml also exerted a suppressive effect on TARC production from PBL in response to Cry j 1 and IL-4 stimulation in vitro. Conclusion: This inhibitory action of FEX may be partially responsible for the attenuating effect of the agent on allergic diseases.
Reduced CD40L Expression on ex vivo Activated CD4+ T-Lymphocytes from Patients with Excellent Renal Allograft Function Measured with a Rapid Whole Blood Flow Cytometry Procedure
Authors: Lederer Stephan R. , Friedrich Nicole , Gruber Rudolf , Landgraf Rüdiger , Toepfer Marcel , Sitter Thomas
Published: February 2004

Background: The CD40-CD40L (CD154) costimulatory pathway plays a critical role in the pathogenesis of kidney allograft rejection. In renal transplant biopsies, CD4+CD40L+ graft-infiltrating cells were detected during chronic rejection in contrast to acute rejection episodes. Using a rapid noninvasive FACS procedure, we were able to demonstrate CD40L upregulation in peripheral blood of patients with chronic renal allograft dysfunction. Materials and Methods: Whole blood from recipients of renal allografts was stimulated with PMA and ionomycin and measured by flow cytometry. Patients were assigned to three groups based on transplant function. Group 1: 26 patients with excellent renal transplant function; group 2: 28 patients with impaired transplant function; group 3: 14 patients with chronic allograft dysfunction and group 4: 8 healthy controls. Results: The median percentage ±SEM of CD4+/CD40L+cells stimulated ex vivo at 10 ng/ml PMA was as follows: group 1: 28.3 ± 4.1%; group 2: 18.4 ± 2.4%; group 3: 50.1 ± 5.0% and group 4: 40.4 ± 3.4%. Subdivisions of groups 2 and 3 resulted in different CD40L expression patterns. Patients with increased serum creatinine since the initial phase after transplantation (groups 2a and 3a) revealed a higher percentage of CD4+CD40L+ cells than patients showing a gradual increase over time (groups 2b and 3b). Consequently, patients of group 3a exhibited a significantly reduced transplant function compared with those of group 3b. Conclusion: After PMA + ionomycin stimulation, patients with excellent kidney graft function displayed significantly reduced expression of CD40L surface molecules on CD4+ cells early after transplantation. Those with a chronic dysfunction of the renal graft showed significantly more CD4+ cells expressing CD40L compared to the other transplanted groups. These results demonstrate that the percentage of CD4+CD40L+ cells stimulated ex vivo in peripheral blood may be a valuable marker for chronic allograft nephropathy.
Prenatal Ethanol Administration: Effects on IgG Absorption during Postnatal Development in the Rat Intestine
Authors: Bhalla Sonali , Kaur Kamaljit , Mahmood Akhtar , Mahmood Safrun
Published: February 2004

The effect of feeding 1 ml of 30% ethanol to pregnant female rats during gestation on the IgG absorption has been studied in the developing intestine. Pups born to dams fed ethanol during gestation exhibited a significant decline in body weight (p < 0.01), intestinal weight (p < 0.01), and intestinal length (p < 0.05) as compared with the controls. Intestinal weight to body weight or intestinal weight to intestinal length ratios were essentially similar under these conditions. The intestinal absorption of IgG was considerably reduced in 12-day-old pups (p < 0.01) exposed to ethanol in utero as compared with the control group. A similar decrease in the binding of [125I]IgG to microvillus membranes was observed on days 12 and 20 under these conditions. Northern blot analysis revealed low levels of mRNA encoding IgG Fc receptor in ethanol-exposed pups as compared with the controls. These findings suggest that prenatal ethanol ingestion impairs the absorption of IgG as a consequence of the downregulation of IgG Fc receptor expression in the rat intestine.
Protective Effect of Pentoxifylline on Volume-Induced Lung Injury in Newborn Piglets
Authors: Smalling Jr. William E. , Suguihara Cleide , Huang Jian , Rodriguez Maria M. , Bancalari Eduardo
Published: February 2004

To evaluate the efficacy of pentoxifylline (PTXF) in the attenuation of lung inflammation during volume-induced lung injury (VILI) in newborn piglets, 17 newborn piglets were mechanically ventilated with a large tidal volume (50 ml/kg) for a period of 8 h. They were randomly assigned to a placebo (PL, n = 9) or a treatment group (PTXF, n = 8) that received PTXF (20 mg/kg as a bolus, followed by a continuous infusion of 5 mg/kg/h). Hemodynamics, lung mechanics and arterial blood gases were measured during the 8 h of study. Serum and tracheoalveolar fluid (TAF) platelet-activating factor (PAF) and thromboxane (TXB2) levels were obtained at baseline and at 8 h, while lung tissue myeloperoxidase (MPO) and wet to dry weight were assessed after the completion of the study. In the PL group, a marked increase in TAF PAF and TXB2 levels was observed only in TAF, suggesting that the inflammatory process was localized within the lungs. A significant decrease in lung tissue MPO activity (p < 0.005) and lung wet to dry weight ratio (p < 0.04) was observed in the PTXF group. There were no differences in hemodynamics, arterial blood gases or lung mechanics measurements between groups. A significant reduction in pulmonary inflammatory response was observed during VILI in the PTXF pretreated animals. These results suggest that PTXF may be effective in modulating lung inflammation associated with mechanical ventilation in neonates.
Influence of Feeding Formula and Breast Milk Fortifier on Lymphocyte Subsets in Very Low Birth Weight Premature Newborns
Authors: Tarcan Aylin , Gürakan Berkan , Tiker Filiz , Özbek Namık
Published: February 2004

Background: It is well known that breast-feeding protects the newborn from infectious diseases. This is especially important for very low birth weight preterm infants, whose immune systems are immature. In this study we investigated how a milk fortifier and replacement formula affected lymphocyte subsets in preterm infants. Method: The study assessed the effects of different types of feeding (human milk, n = 14; fortified human milk, n = 16; formula, n = 14) on lymphocyte subsets in 44 very low birth weight preterm infants. For each baby, two consecutive blood samples were collected 7–10 days apart during the full enteral feeding period. For each sample, the percentages of CD3+ (pan-T), CD19+ (B-cell), CD4+ (T-helper), CD8+ (T-suppressor), and CD3–CD16/56+ (natural killer cell) lymphocytes were measured in a flow cytometer, and the absolute count for each subset was calculated based on the total lymphocyte count. Within each feeding group, the absolute numbers of each lymphocyte subset in the two consecutive samples were compared. Also, the mean absolute counts for each cell type were compared among the 3 groups for the first set of blood samples, and the same comparisons were made for the second set. Results: The mean number of CD3–CD16/56+ cells in the formula-fed infants was significantly lower than the corresponding means in the groups fed human milk alone and fortified human milk (p = 0.037). Conclusion: The findings suggest that babies fed formula have different lymphocyte subset compositions than those fed breast milk or fortified breast milk.
Recombinant factor VIIa partially reverses the inhibitory effect of fondaparinux on thrombin generation after tissue factor activation in platelet rich plasma and whole blood
Authors: Depasse François , Chakroun Tahar , Samama Meyer , Elalamy Ismail , Gerotziafas Grigoris
Published: February 2004

Fondaparinux (Arixtra®), a specific AT-dependent FXa inhibitor, is effective and safe in the prevention and treatment of venous thromboembolism, but some major hemorrhagic events may occur. No specific antidote to fondaparinux has been proposed. Recombinant FVIIa (Novoseven®) could be used as an haemostatic treatment, but this option has not been well documented. We studied the effect of rFVIIa (1 µg/ml) on the inhibition of thrombin generation induced by fondaparinux (0.1µg/ml to 1 µg/ml). Coagulation was triggered in platelet rich plasma (PRP) or in whole blood by recalcification in the presence of diluted thromboplastin. In PRP thrombin generation was assessed using the thrombinoscope assay. In whole blood, prothrombin activation was assessed by measuring the kinetics of F1+2
formation using an ELISA assay. Fondaparinux at concentrations equal or greater than 0.5 µg/ml prolonged the initiation phase of thrombin generation, and reduced the velocity of prothrombin activation. It also decreased by 60% the endogenous thrombin potential. In the presence of fondaparinux (0.5 µg/ml to 1 µg/ml) rFVIIa accelerated the initiation phase of thrombin generation, but it did not significantly increase the endogenous thrombin potential. However, rFVIIa did not completely reverse the inhibitory effect of fondaparinux on the parameters of thrombin generation and prothrombin activation. This study shows that rFVIIa accelerates thrombin generation, but does not completely reverse the inhibitory effect of fondaparinux on thrombin generation. The potential clinical use of rFVIIa as haemostatic treatment of major bleedings related to fondaparinux has to be evaluated.
The 'Teachers' of Mani in the Acta Archelai and Simon Magus
Authors: Spät Eszter
Published: February 2004

This paper aims to prove that the biography of Mani in the Acta Archelae of Hegemonius, which contains a great number of completely fictitious elements, was in fact drawn up on the file of Simon Magus, pater omnium haereticorum, using the works of heresiologists and the apocryphal acts, especially the Pseudo-Clementine Recognitiones, as a model and source. There are a great number of elements in this Vita Manis that bear a strong resemblance to the well known motives of Simon's life. Projecting Simon's life over that of Mani serves as tool to reinforce the image of Mani that Hegemonius tried to convey: that of just another 'run of the mill' heretic, one in the long line of the disciples of Simon, and a fraud and devoid of any originality.
In Quest of the Third Heaven: Paul & his Apocalyptic Imitators
Authors: Harrison J.R.
Published: February 2004

It is an irony of history that by late antiquity Paul had become the authority figure he never was during his lifetime. However, by the subapostolic and patristic periods Paul's apostolic authority was no longer considered quite so controversial. From 200 AD onwards Paul's letters were regularly cited alongside the Gospels and the Old Testament as 'Scripture'. It is therefore no surprise that the premier apocalyptic theologian of the New Testament would spawn several apocalyptic imitators. Two 'Apocalypses of Paul' have come down to us from antiquity, one gnostic, the other Christian. After discussing each work, the article asks to what extent the historical Paul would have agreed with these later works written in his name. The article will demonstrate how differing ecclesiastical traditions appropriated Paul for their own theological and social agendas instead of allowing the apostle to the Gentiles to speak to his first-century context
The Good Samaritan in Ancient Christianity
Authors: Roukema Riemer
Published: February 2004

For modern readers the parable of the Good Samaritan clearly has an ethical meaning. Although in ancient Christianity this tenor was not fully neglected, the parable was usually interpreted allegorically, the Samaritan being seen as Christ the Saviour of sinners, who had been robbed by the devil. The present article gives a survey of the various interpretations and elaborations of Irenaeus, Clement of Alexandria, an anonymous presbyter, Origen, Gregory Thaumaturgus, the Gospel of Philip, Ambrose, Augustine, and Ephrem the Syrian. It concludes with some remarks on Christian charity in the first centuries C.E. which may in part have provided the hermeneutical context of the allegorization of the parable. It is argued that before Christians were ready to identify themselves with the Samaritan, they first, before their conversion, had identified themselves with the wounded man helped by the Samaritan, who was represented by other Christians.
Mechanism of Electron Conduction in Self‐Assembled Alkanethiol Monolayer Devices
Authors: LEE TAKHEE , WANG WENYONG , REED M A
Published: February 2004

Abstract: Electron tunneling through self‐assembled monolayers (SAMs) of alkanethiols was investigated using nanometer scale devices that allow temperature‐dependent current‐voltage, I(V, T), measurements. The I(V, T) measurement results show, for the first time, temperature‐independent electron transport characteristics, proving direct tunneling as the transport mechanism in alkanethiol SAMs. The measured tunneling currents can be fitted with theoretical calculations using the modified rectangular barrier model of direct tunneling with a barrier height ΦB= 1.42 ± 0.04 eV and a non‐ideal barrier factor α= 0.65 ± 0.01 (that may correspond to effective mass of 0.42 m). From the length‐dependent conduction measurement on different alkanethiols of various lengths, the tunneling current exhibits exponential dependence on the molecular length, d, as I ∝ exp(−βd), where β is a decay coefficient that was found to be bias‐dependent and agrees with the existing theory of direct tunneling. A zero field decay coefficient β0 of 0.79 ± 0.01 Å−1 was obtained.
Electrical Characterization of Metal—Molecule—Silicon Junctions
Authors: WANG W , LEE T , KAMDAR M , REED MA , STEWART MP , HWANG JJ , TOUR JM
Published: February 2004

Abstract: Direct assembly of molecules onto silicon surfaces is of particular interest for potential employment in hybrid organic‐semiconductor devices. In the study we report here, aryl diazonium salts were used to assemble covalently bound molecular groups on a hydride‐passivated, oxide‐free n‐type Si(111) surface. The reaction of 4‐(trimethylsilylethynyl)benzenediazonium tetrafluoroborate generates a molecular layer of 4‐(trimethylsilylethynyl)phenylene (TMS‐EP) on the n++‐Si(111) surface. The monolayer modifies the electrical properties of the interface and exhibits nonlinear current‐voltage characteristics, as compared with the ohmic behavior observed from metal‐n++‐Si(111) junctions. The result of current‐voltage measurements at variable temperatures (from 300 to 10 K) on samples made with the TMS‐EP molecule does not show significant thermally‐activated transport, indicating that tunneling is the dominant transport mechanism. The measured data is compared to a tunneling model.
NEGF‐HF Method in Molecular Junction Property Calculations
Authors: GALPERIN MICHAEL , NITZAN ABRAHAM
Published: February 2004

Abstract: Electron‐electron interaction is an essential issue in predicting the properties of a molecular conduction junction. An accurate treatment requires taking proper account of the potential distribution across the junction as well as for the change in electronic structure under the external voltage drop. Another important point is the necessity to treat molecules as open quantum systems. In this paper we address these issues within the framework of the non‐equilibrium Green's function formalism at the Hartree‐Fock level (NEGF‐HF), which permits a self‐consistent treatment of the problem. We apply the method to study the experimentally observed asymmetry in the I‐V curves with respect to polarity of voltage bias in Hg‐Au junctions containing bilayers of alkanethiols of various chain lengths. The origin of the effect is suggested to be the asymmetric behavior of the character of the highest occupied molecular orbital (HOMO) of the junction at opposite biases, which leads to different effective barriers for electron transfer across the junction at opposite signs of the voltage drop. The calculated potential profile shows the capacitor‐like nature for the junction with the weak link.
A Simple Theoretical Model to Study the Voltage Dependence of the Electronic Structure of Phenyl Ethylene Oligomers
Authors: SIMÓN‐MANSO YAMIL , GONZALEZ CARLOS , MUJICA VLADIMIRO , ARAY YOSSLEN , MARQUEZA MANUEL
Published: February 2004

Abstract: Although very few measurements have appeared in the open literature and there seems to be a controversy about the existence of the NDR phenomenon in molecules, the prospects of building such systems have attracted significant attention. In the work reported in this paper we used a model based on DFT calculations of the electronic structure of the 2′‐amino‐4,4′‐di(ethynylphenyl)‐5′‐nitro‐1‐benzenethiolate molecule (previously reported to exhibit NDR behavior) in a capacitor‐like electric field that mimics the potential spatial profile of the junction. Our results suggest that in these systems, there seems to be a correlation between a substantial charge density rearrangement of the neutral bridge at a threshold voltage and the NDR behavior observed in previous experiments. Our results highlight the importance of inclusion of the field in the study of electrified interfaces. We applied this model to a fluorine‐substituted conjugated diethynylphenyl molecule and found that these calculations predict similar behavior. Results based on extended system calculations, including electrode‐molecule interactions, confirm the validity of the model based on the isolated molecule and suggest the use of these simple models to rationally design molecular devices with similar switching characteristics.
Molecular Landers as Probes for Molecular Device—Metal Surface Interactions
Authors: GHOSH SUKHEN C. , ZHU XIAOXIANG , SECCHI ANDREA , SADHUKHAN SUBIR K. , GIRDHAR NAVDEEP K. , GOURDONA ANDRÉ
Published: February 2004

Abstract: Specifically designed series of molecules (landers), comprising a central rigid polyaromatic core and several spacers that decouple the board from the metallic surface, have been synthesized. UHV‐STM studies, on one hand, have shown important distortions of the molecule by interaction with the substrate. On the other hand, surface restructuring results from the presence of the molecules.
Optical Switching in Chiropticenes
Authors: PARAKKA JAMES P. , SCHUMAKER ROBERT R. , THOBURN JOHN D. , KESLER BRENDA S. , BRANZ STEPHEN E.
Published: February 2004

Abstract: Chiropticenes™ are a novel class of predesigned chiral molecular switches that are triggered and controlled by a combination of both light and electric field. Chiropticenes contain an optically active (chiral) center and, as a consequence, provide two accessible equal energy bistable states resembling the molecular elements of binary logic. Structural engineering of the basic switch design is investigated to modulate the thermal and optical switching behavior of the resulting compounds. A simple screening methodology is presented to detect switching behavior in the solid state employing standard NMR and FT‐IR spectroscopy. Validation of this method is demonstrated by the switching properties of newly synthesized anthraquinone dye based Chiropticenes. Functioning as a chiroptical dipole switch, Chiropticenes promise broad applications in emerging optoelectronic and molecular electronic technologies.
Electrical Transport Study of Phenylene‐Based π‐Conjugated Molecules in a Three‐Terminal Geometry
Authors: LEE JEONG‐O , LIENTSCHNIG GÜNTHER , WIERTZ FRANK G.H. , STRUIJK MARTIN , JANSSEN RÉNE A.J. , EGBERINK RICHARD , REINHOUDT DAVID N. , GRIMSDALE ANDREW C. , MÜLLEN KLAUS , HADLEY PETER , DEKKERA CEES
Published: February 2004

Abstract: We fabricated three‐terminal devices with conjugated molecules. Two different device layouts were used to measure both very short molecules (with one or two benzene rings) and relatively long ones (as long as 8 nm). To achieve an optimum gate effect, we used aluminum gates covered with a very thin native oxide layer. Molecules with thiol end groups were positioned between the source and drain electrodes by self‐assembly. The device yield was low for short molecules, most likely due to defects in the self‐assembled monolayers. Most of the devices made with short molecules did not show any gate effect at all; a small gate effect was only observed in two samples made with 1,3‐benzenedithiol. Some devices showed clear negative differential conductance peaks. In some devices made with long molecules, we observed a small change of conductance with gate voltage.
Analysis of Electron Transfer in Substituted Biphenylmethane
Authors: CACELLI IVO , FERRETTI ALESSANDRO , GIRLANDA MICHELE , MACUCCI MASSIMO
Published: February 2004

Abstract: We present an analysis of electron transfer in a molecular structure containing two phenyl rings connected by a methylene barrier, with the addition of a donor group (NH2) on one ring and an acceptor group (NO2) on the other. Such molecules are among those currently being considered for the implementation of molecular circuits for information processing. We have performed both a study of the response of electron polarization to the application of an external electrostatic perturbation, and an analysis of the time‐dependent behavior of electron transfer across the barrier. A detailed evaluation of the electron affinity and of the ionization energy of the molecular structure under investigation has also been performed, obtaining results that show the inadequacy of representations in terms of simple HOMO and LUMO orbitals.
CrossNets: High‐Performance Neuromorphic Architectures for CMOL Circuits
Authors: LIKHAREV KONSTANTIN , MAYR ANDREAS , MUCKRA IBRAHIM , TÜREL ÖZGÜR
Published: February 2004

Abstract:The exponential,Moore's Law, progress of electronics may be continued beyond the 10‐nm frontier if the currently dominant CMOS technology is replaced by hybridCMOLcircuits combining a silicon MOSFET stack and a few layers of parallel nanowires connected by self‐assembled molecular electronic devices. Such hybrids promise unparalleled performance for advanced information processing, but require special architectures to compensate for specific features of the molecular devices, including low voltage gain and possible high fraction of faulty components. Neuromorphic networks with their defect tolerance seem the most natural way to address these problems. Such circuits may be trained to perform advanced information processing including (at least) effective pattern recognition and classification. We are developing a family of distributed crossbar network (CrossNet) architectures that permit the combination of high connectivity neuromorphic circuits with high component density. Preliminary estimates show that this approach may eventually allow us to place a cortex‐scale circuit with about 1010neurons and about 1014synapses on an approximately 10 × 10 cm2silicon wafer. Such systems may provide an average cell‐to‐cell latency of about 20 nsec and, thus, perform information processing and system training (possibly including self‐evolution after initial training) at a speed that is approximately six orders of magnitude higher than in its biological prototype and at acceptable power dissipation.
Conductive Probe AFM Measurements of Conjugated Molecular Wires
Authors: ISHIDA TAKAO , MIZUTANI WATARU , LIANG TIEN‐TZU , AZEHARA HIROAKI , MIYAKE KOJI , SASAKI SHINYA , TOKUMOTO HIROSHI
Published: February 2004

Abstract: The electrical conduction of self‐assembled monolayers (SAMs) made from conjugated molecules was measured using conductive probe atomic force microscopy (CP‐AFM), with a focus on the molecular structural effect on conduction. First, the electrical conduction of SAMs made from phenylene oligomer SAMs was measured. The resistances through the monolayers increased exponentially with an increase in molecular length and the decay constants of transconductance β were about 0.45 to 0.61 Å−1 measured at lower bias region. We further investigated the influence of applied load on the resistances. The resistances through terphenyl SAMs increased with an increase in the applied load up to 14 nN. Second, using an insertion technique into insulating alkanethiol SAMs, the electrical conduction of single conjugated terphenyl methanethiol and oligo(para‐phenylenevinylene) (OPV) molecules embedded into insulating alkanethiol SAMs were measured. Electrical currents through these single molecules of OPVs were estimated to be larger than those through single terphenyl molecules, suggesting that the OPV structure can increase the electrical conduction of single molecules. Third, apparent negative differential resistance (NDR) was observed at higher bias measurements of SAMs. The appearance of NDR might be related to roughness of SAM surface, because apparent NDR was often observed on rough surfaces. In any case, the tip‐molecule contact condition strongly affected carrier transport through metal tip/SAM/metal junction.
A Protein‐Based Three Terminal Electronic Device
Authors: RINALDI ROSS , MARUCCIO GIUSEPPE , BIASCO ADRIANA , VISCONTI PAOLO , ARIMA VALENTINA , CINGOLANI ROBERTO
Published: February 2004

Abstract: Because of their natural functional characteristics, involving inter‐ and intramolecular electron transfer, metalloproteins are good candidates for biomolecular nanoelectronics. In particular, blue copper proteins, such as azurin, can bind gold via a disulfide site present on its surface and they have a natural electron transfer activity that can be exploited for the realization of molecular switches whose conduction state can be controlled by tuning their redox state through an external voltage source. We report on the implementation of a prototype of protein transistor operating in air and in the solid state, based on this class of proteins. The three terminal devices exhibit various functions depending on the relative source‐drain and gate‐drain voltages bias, opening a way to the implementation of a new generation of logic architectures.
Single‐Molecule Designs for Electric Switches and Rectifiers
Authors: KORNILOVITCH PAVEL , BRATKOVSKY ALEXANDER , WILLIAMS STANLEY
Published: February 2004

Abstract: A design for molecular rectifiers is proposed. Current rectification is based on the spatial asymmetry of a molecule and requires only one resonant conducting molecular orbital. Rectification is caused by asymmetric coupling of the orbital to the electrodes, which results in asymmetric movement of the two Fermi levels with respect to the orbital under external bias. Results from numerical studies of the family of suggested molecular rectifiers, HS−(CH2)n−C6H4−(CH2)m−SH, are presented. Current rectification ratios in excess of 100 are achievable for n= 2 and m > 6. A class of bistable stator‐rotor molecules is proposed. The stationary part connects the two electrodes and facilitates electron transport between them. The rotary part, which has a large dipole moment, is attached to an atom of the stator via a single sigma bond. Electrostatic bonds formed between the oxygen atom of the rotor and hydrogen atoms of the stator make the symmetric orientation of the dipole unstable. The rotor has two potential minima with equal energy for rotation about the sigma bond. The dipole can be flipped between the two states by an external electric field. Both rotor‐orientation states have asymmetric current‐voltage characteristics that are the reverse of each other, so they are distinguishable electrically. Theoretical results on conformation, energy barriers, retention times, switching voltages, and current‐voltage characteristics are presented for a particular stator‐rotor molecule. Such molecules could be the base for single‐molecule switches, reversible diodes, and other molecular electronic devices.
TranSIESTA: A Spice for Molecular Electronics
Authors: STOKBRO KURT , TAYLOR JEREMY , BRANDBYGE MADS , ORDEJÓN PABLO
Published: February 2004

Abstract: Our recently developed method, TranSIESTA, enables modelling of molecular electronic devices under operation conditions. The method is based on density functional theory, and calculates the self‐consistent electronic structure of a nanostructure coupled to three‐dimensional electrodes with different electrochemical potentials. It uses a full atomistic ab initio description of both the electrodes and the nanoscale device. The calculations reveal information about the scattering states, transmission coefficients, electron current, and non‐equilibrium forces in the systems. In this paper we use the method to investigate the electrical properties of three ring phenyl‐ethynylene oligomers (OPE). We present results for the electrical effect of side groups and molecular conformations of the molecules. The calculations indicate that molecular switching and negative differential conductance (NDC) are related to rotations of the middle phenyl ring.
The Appropriateness of Density‐Functional Theory for the Calculation of Molecular Electronics Properties
Authors: REIMERS JEFFREY R. , CAI ZHENG‐LI , BILIĆ ANTE , HUSH NOEL S.
Published: February 2004

Abstract: As molecular electronics advances, efficient and reliable computation procedures are required for the simulation of the atomic structures of actual devices, as well as for the prediction of their electronic properties. Density‐functional theory (DFT) has had widespread success throughout chemistry and solid‐state physics, and it offers the possibility of fulfilling these roles. In its modern form it is an empirically parameterized approach that cannot be extended toward exact solutions in a prescribed way, ab initio. Thus, it is essential that the weaknesses of the method be identified and likely shortcomings anticipated in advance. We consider four known systematic failures of modern DFT: dispersion, charge transfer, extended π conjugation, and bond cleavage. Their ramifications for molecular electronics applications are outlined and we suggest that great care is required when using modern DFT to partition charge flow across electrode‐molecule junctions, screen applied electric fields, position molecular orbitals with respect to electrode Fermi energies, and in evaluating the distance dependence of through‐molecule conductivity. The causes of these difficulties are traced to errors inherent in the types of density functionals in common use, associated with their inability to treat very long‐range electron correlation effects. Heuristic enhancements of modern DFT designed to eliminate individual problems are outlined, as are three new schemes that each represent significant departures from modern DFT implementations designed to provide a priori improvements in at least one and possible all problem areas. Finally, fully semiempirical schemes based on both Hartree‐Fock and Kohn‐Sham theory are described that, in the short term, offer the means to avoid the inherent problems of modern DFT and, in the long term, offer competitive accuracy at dramatically reduced computational costs.
Unimolecular Rectifiers and Proposed Unimolecular Amplifier
Authors: METZGER ROBERT M.
Published: February 2004

Abstract: The rectification by three molecules that form Langmuir‐Blodgett monolayers between gold electrodes is reviewed, along with a proposal for the means to obtain gain in a unimolecular amplifier, the molecular analog of a bipolar junction transistor.
Molecular Assembly and Self‐Assemblya: Molecular Nanoscience for Future Technologies
Authors: DE WILD M , BERNER S , SUZUKI H , RAMOINO L , BARATOFF A , JUNGA T A.
Published: February 2004

Abstract: In this review the emerging science of single molecules is discussed in the perspective of nanoscale molecular functions and devices. New methods for the controlled assembly of well‐defined molecular nanostructures are presented: self assembly and single molecular positioning. The observation and selective modification of conformation, electronics, and molecular mechanics of individual molecules and molecular assemblies by scanning probes is demonstrated. To complement this scientific review, some of the possible consequences and visions for future developments are discussed, as far as they derive from the presented systems. The prospects of nanoscale science to stimulate technological evolution are exemplified.
A Three Terminal Ring Interferometer Logic Gate
Authors: Yi J , Cuniberti G
Published: February 2004

Abstract: We propose a carbon‐based logic gate where AND, OR, and XOR logic operations are available. It consists of a carbon nanotube (CNT) ring coupled to three external CNT‐leads, two of them used as input channels, and the third as the output channel. The total transmission for two inputs displays characteristic interference effects. The constructive interference leads to total transmission significantly larger than that for a single input and validates AND gates, whereas the destructive interference corresponds to XOR gates. For OR gates a negligible interference between the transmittance of each single inputs is needed.
Scalability Simulations for Nanomemory Systems Integrated on the Molecular Scale
Authors: ZIEGLER MATTHEW M. , PICCONATTO CARL A. , ELLENBOGEN JAMES C. , DEHON ANDRÉ , WANG DELI , ZHONG ZHAOHUI , LIEBER CHARLES M.
Published: February 2004

Abstract:Simulations were performed to assess the prospective performance of a 16 Kbit nanowire‐based electronic nanomemory system. Commercial off‐the‐shelf microcomputer system modeling software was applied to evaluate the operation of an ultra‐dense storage array. This array consists of demonstrated experimental non‐volatile nanowire diode switches, plus encoder‐decoder structures consisting of demonstrated experimental nanowire‐based nanotransistors, with nanowire interconnects among all the switching devices. The results of these simulations suggest that a nanomemory of this type can be operated successfully at a density of 1011bits/cm2. Furthermore, modest device alterations and system design alternatives are suggested that might improve the performance and the scalability of the nanomemory array. These simulations represent early steps toward the development of a simulation‐based methodology to guide nanoelectronic system design in a manner analogous to the way such methodologies are used to guide microelectronic system design in the silicon industry.
Force production and flow structure of the leading edge vortex on flapping wings at high and low Reynolds numbers
Authors: Birch James M. , Dickson William B. , Dickinson Michael H.
Published: February 2004

The elevated aerodynamic performance of insects has been attributed in part to the generation and maintenance of a stable region of vorticity known as the leading edge vortex (LEV). One explanation for the stability of the LEV is that spiraling axial flow within the vortex core drains energy into the tip vortex, forming a leading-edge spiral vortex analogous to the flow structure generated by delta wing aircraft. However, whereas spiral flow is a conspicuous feature of flapping wings at Reynolds numbers (Re) of 5000, similar experiments at Re=100 failed to identify a comparable structure. We used a dynamically scaled robot to investigate both the forces and the flows created by a wing undergoing identical motion at Re of∼120 and ∼1400. In both cases, motion at constant angular velocity and fixed angle of attack generated a stable LEV with no evidence of shedding. At Re=1400, flow visualization indicated an intense narrow region of spanwise flow within the core of the LEV, a feature conspicuously absent at Re=120. The results suggest that the transport of vorticity from the leading edge to the wake that permits prolonged vortex attachment takes different forms at different Re.
Central control of electric signaling behavior in the mormyridBrienomyrus brachyistius: segregation of behavior-specific inputs and the role of modifiable recurrent inhibition
Authors: Carlson Bruce A. , Hopkins Carl D.
Published: February 2004

Like all mormyrid fish, Brienomyrus brachyistius produces an electric organ discharge (EOD) with a constant waveform and variable sequence of pulse intervals (SPI). Periodic bursts fall into two display categories termed `scallops' and `accelerations', with a third category termed `rasps'that appears to combine the two. The medullary EOD command nucleus (CN)receives excitatory input from the midbrain precommand nucleus (PCN) and the thalamic dorsal posterior nucleus (DP), both of which are regulated by a recurrent inhibitory projection from the ventroposterior nucleus of the torus semicircularis (VP). We tested the following hypotheses: (1) PCN and DP are responsible for generating different burst types (scallops and accelerations,respectively), (2) differences in the strength of recurrent inhibition are related to physiological differences between PCN and DP and (3) recurrent inhibition regulates the resting electromotor rhythm, while disinhibition releases PCN and DP, allowing them to generate bursts. Iontophoresis of the excitatory neurotransmitter l-glutamate (l-Glu) into DP led to acceleration-like output patterns, while in PCN it led to scallop-like output patterns. Iontophoresis of the inhibitory neurotransmitterγ-amino-butyric acid (GABA) into DP and PCN led to an elongation of intervals, as did iontophoresis of l-Glu into VP. Iontophoresis of the GABAA receptor blocker bicuculline methiodide (BMI) into DP and PCN induced repetitive bursting behavior and eliminated differences in the effects of l-Glu iontophoresis in the two nuclei. These results support our three hypotheses, suggesting that production of different communication behaviors may be regulated by spatially distinct groups of neurons, and recurrent inhibition and disinhibition may play an active role in driving and shaping such behaviors.
Intracellular calcium translocation during the contraction–relaxation cycle in scorpionfish swimbladder muscle
Authors: Suzuki Suechika , Hino Naoki , Sugi Haruo
Published: February 2004

To examine intracellular Ca2+ translocation during the contraction–relaxation cycle in vertebrate striated muscle, electron probe X-ray microanalysis was performed on the swimbladder muscle (SBM) fibres of a scorpionfish Sebastiscus marmoratus. The SBM fibres were rapidly frozen at rest, during contraction and at various times after the onset of relaxation. Changes in calcium distribution in the components of the sarcoplasmic reticulum (SR) were examined on the SBM fibre cryosections. In resting fibres, the calcium concentration was highest around the boundary between the A and I bands (A–I boundary), where the terminal cisternae(TC) were located. In contracting fibres, the calcium concentration decreased around the A–I boundary, while it increased in all other regions of the sarcomere, indicating Ca2+ release from the TC into the myoplasm. During relaxation, the calcium concentration first increased around the regions, where the fenestrated collars (FC) and the longitudinal tubules (LT)were located, and then gradually returned to the levels seen in resting fibres. These results support the view that, after the onset of relaxation in the SBM fibres, Ca2+ in the myoplasm is first taken up by the FC and the LT, and then gradually returns to the TC.
Microspectrophotometry of visual pigments and oil droplets in a marine bird, the wedge-tailed shearwaterPuffinus pacificus: topographic variations in photoreceptor spectral characteristics
Authors: Hart Nathan S.
Published: February 2004

Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A1-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (λmax) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet(VS, λmax 406 nm), short (SWS, λmax 450 nm), medium (MWS, λmax 503 nm) or long (LWS,λ max 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (λcut) at 445 (C-type),506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm λmax visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a λcut at 413 nm. The retina had a horizontal band or `visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.
Stimulation by cadmium of myohemerythrin-like cells in the gut of the annelidNereis diversicolor
Authors: Demuynck Sylvain , Bocquet-Muchembled Beatrice , Deloffre Laurence , Grumiaux Fabien , Leprêtre Alain
Published: February 2004

Isolated guts of Nereis diversicolor revealed the existence of a cadmium-binding protein, the MPII, belonging to the group of hemerythrins and myohemerythrins. The presence of MPII in the cells of the intestine was demonstrated by immunocytochemistry, using anti-MPII, a monoclonal antibody. In addition, using in situ hybridization and northern blotting, it was shown that MPII-cells are the site of synthesis of this molecule. Exposure of the worms to cadmium led to the cellular activation process of MPII-cells(i.e. transformation of the nucleolus, development of the endoplasmic reticulum and the Golgi apparatus), although MPII mRNA transcript levels were unchanged. Enzyme-linked immunosorbent assay (ELISA) of gut extracts revealed that MPII levels were increased after exposure to Cd, so it appears that this protein is synthesized as a response to Cd exposure without any new synthesis of mRNA. This mechanism of regulation is quite similar to that reported in the case of mammalian ferritin and may be involved in the regulation of Cd levels in this worm.
The effect of molluscan glue proteins on gel mechanics
Authors: Pawlicki J. M. , Pease L. B. , Pierce C. M. , Startz T. P. , Zhang Y. , Smith A. M.
Published: February 2004

Several molluscs have been shown to alternate between a non-adhesive trail mucus and a similar gel that forms a strong glue. The major structural difference between the two secretions is the presence of specific proteins in the adhesive mucus. The present study identifies similar proteins from the glue of the slug Arion subfuscus and the land snail Helix aspersa. To investigate the role played by these proteins in adhesion,the proteins were isolated from the adhesive mucus of different molluscs and added to commercial polymer solutions. The effect was observed qualitatively,and quantified using a dynamic rheometer. The isolated proteins triggered gelling or visible stiffening of agar, pectin and polygalacturonic acid. The effect was stronger on more negatively charged polymers. The effect of the proteins was concentration dependent with an optimal concentration of 1–1.5 mg ml–1, and was weakened when their structure changed. Other proteins and carbohydrates found in the adhesive mucus had no clear mechanical effect on gels. These findings show that the addition of these proteins to large, anionic polymers plays a central role in the formation of a glue from a mucus-like secretion. Such a mechanism may be common among invertebrates, and it may guide biomimetic approaches in the development of glues and gels.
Unsteady aerodynamic forces of a flapping wing
Authors: Wu Jiang Hao , Sun Mao
Published: February 2004

The unsteady aerodynamic forces of a model fruit fly wing in flapping motion were investigated by numerically solving the Navier–Stokes equations. The flapping motion consisted of translation and rotation [the translation velocity (ut) varied according to the simple harmonic function (SHF), and the rotation was confined to a short period around stroke reversal]. First, it was shown that for a wing of given geometry with ut varying as the SHF, the aerodynamic force coefficients depended only on five non-dimensional parameters, i.e. Reynolds number (Re), stroke amplitude (Φ), mid-stroke angle of attack(αm), non-dimensional duration of wing rotation(Δτr) and rotation timing [the mean translation velocity at radius of the second moment of wing area (U), the mean chord length (c) and c/U were used as reference velocity, length and time, respectively]. Next, the force coefficients were investigated for a case in which typical values of these parameters were used (Re=200;Φ=150°; αm=40°; Δτr was 20%of wingbeat period; rotation was symmetrical). Finally, the effects of varying these parameters on the force coefficients were investigated.

In the Re range considered (20–1800), when Re was above ∼100, the lift(C̄L) and drag(C̄D) coefficients were large and varied only slightly with Re (in agreement with results previously published for revolving wings); the large force coefficients were mainly due to the delayed stall mechanism. However, when Re was below∼100, C̄L decreased and C̄D increased greatly. At such low Re, similar to the case of higher Re, the leading edge vortex existed and attached to the wing in the translatory phase of a half-stroke; but it was very weak and its vorticity rather diffused, resulting in the small C̄L and large C̄D. Comparison of the calculated results with available hovering flight data in eight species(Re ranging from 13 to 1500) showed that when Re was above∼100, lift equal to insect weight could be produced but when Rewas lower than ∼100, additional high-lift mechanisms were needed.

In the range of Re above ∼100, Φ from 90° to 180°and Δτr from 17% to 32% of the stroke period (symmetrical rotation), the force coefficients varied only slightly with Re, Φand Δτr. This meant that the forces were approximately proportional to the square of Φn (n is the wingbeat frequency); thus, changing Φ and/or n could effectively control the magnitude of the total aerodynamic force.

The time course of C̄L(or C̄D) in a half-stroke for ut varying according to the SHF resembled a half sine-wave. It was considerably different from that published previously for ut, varying according to a trapezoidal function (TF) with large accelerations at stroke reversal, which was characterized by large peaks at the beginning and near the end of the half-stroke. However, the mean force coefficients and the mechanical power were not so different between these two cases (e.g. the mean force coefficients for ut varying as the TF were approximately 10% smaller than those for utvarying as the SHF except when wing rotation is delayed).