bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overcoming the Insolubility of Carbon Nanotubes Through High Degrees of Sidewall Functionalization
Authors: Dyke Christopher A. , Tour James M. 
Published: February 2004

AbstractThe use of carbon nanotubes in materials applications has been slowed due to nanotube insolubility and their incompatibility with polymers. We recently developed two protocols to overcome the insoluble nature of carbon nanotubes by affixing large amounts of addends to the nanotube sidewalls. Both processes involve reactions with aryl diazonium species. First, solvent‐free functionalization techniques remove the need for any solvent during the functionalization step. This delivers functionalized carbon nanotubes with increased solubility in organic solvents and processibility in polymeric blends. Additionally, the solvent‐free functionalization process can be done on large scales, thereby paving the way for use in bulk applications such as in structural materials development. The second methodology involves the functionalization of carbon nanotubes that are first dispersed as individual tubes in surfactants within aqueous media. The functionalization then ensues to afford heavily functionalized nanotubes that do not re‐rope. They remain as individuals in organic solvents giving enormous increases in solubility. This protocol yields the highest degree of functionalization we have obtained thus far—up to one in nine carbon atoms on the nanotube has an organic addend. The proper characterization and solubility determinations on nanotubes are critical; therefore, this topic is discussed in detail.
Theoretical Studies on the Smallest Fullerene: from Monomer to Oligomers and Solid States
Authors: Chen Zhongfang , Heine Thomas , Jiao Haijun , Hirsch Andreas , Thiel Walter , Schleyer Paul von Ragué 
Published: February 2004

AbstractHybrid B3LYP and density‐functional‐based tight‐binding (DFTB) computations on the solid‐state structures and electronic properties of the C20 fullerene monomer and oligomers are reported. C20 cages with C2, C2h, Ci, D3d, and D2h symmetries have similar energies and geometries. Release of the very high C20 strain is, in theory, responsible for the ready oligomerization and the formation of different solid phases. Open [2+2] bonding is preferred both in the oligomers and in the infinite one‐dimensional solids; the latter may exhibit metallic character. Two types of three‐dimensional solids, the open [2+2] simple cubic and the body‐centered cubic (bcc) forms, are proposed. The energy of the latter is lower due to the better oligomer bonding. The open [2+2] simple cubic solid should be a conductor, whereas the bcc solids are insulators. The most stable three‐dimensional solid‐state structure, an anisotropically compressed form of the bcc solid, has a HOMO–LUMO gap of approximately 2 eV and a larger binding energy than that of the proposed C36 solid.
Three‐Coordinate Organoboron Compounds BAr2R (Ar = Mesityl, R = 7‐Azaindolyl‐ or 2,2′‐Dipyridylamino‐Functionalized Aryl or Thienyl) for Electroluminescent Devices and Supramolecular Assembly
Authors: Jia Wen‐Li , Bai Dong‐Ren , McCormick Theresa , Liu Qin‐De , Motala Michael , Wang Rui‐Yao , Seward Corey , Tao Ye , Wang Suning 
Published: February 2004

AbstractEight novel three‐coordinate boron compounds with the general formula BAr2L, in which Ar is mesityl and L is a 7‐azaindolyl‐ or a 2,2′‐dipyridylamino‐functionalized aryl or thienyl ligand, have been synthesized by Suzuki coupling, Ullmann condensation methods, or simple substitution reactions (L = p‐(2,2′‐dipyridylamino)phenyl, 1; p‐(2,2′‐dipyridylamino)biphenyl, 2; p‐(7‐azaindolyl)phenyl, 3; p‐(7‐azaindolyl)biphenyl, 4; 3,5‐bis(2,2′‐dipyridylamino)phenyl, 5; 3,5‐bis(7‐azaindolyl)phenyl, 6; p‐[3,5‐bis(2,2′‐dipyridylamino)phenyl]phenyl, 7; 5‐[p‐(2,2′‐dipyridylamino)phenyl]‐2‐thienyl, 8). The structures of 1, 3, and 5–7 have been determined by X‐ray diffraction analyses. These new boron compounds are bright blue emitters. Electroluminescent devices using compound 2 or 8 as the emitter and the electron‐transport layer have been successfully fabricated. Molecular orbital calculations (Gaussian 98) have established that the blue emission of compounds 1–8 originates from charge transfer between the π orbital of the ligand L and the pπ orbital of the boron center. The ability of these boron compounds to bind to metal centers to form supramolecular assemblies was demonstrated by treatment of compound 2 with Zn(O2CCF3)2, which generated a 1:1 chelate complex {2⋅Zn(O2CCF3)2} (10), and also by treatment of compound 4 with AgNO3, yielding a 2:1 coordination compound {(4)2⋅Ag(NO3)} (11). In the solid state, compounds 10 and 11 form interesting head‐to‐head and tail‐to‐tail extended structures that host solvent molecules such as benzene.
Molecular Basis of the Dynamic Strength of the Sialyl Lewis X—Selectin Interaction
Authors: Zhang Xiaohui , Bogorin Daniela F. , Moy Vincent T. 
Published: February 2004

AbstractThe selectins are Ca2+‐dependent cell adhesion molecules that facilitate the initial attachment of leukocytes to the vascular endothelium by binding to a carbohydrate moiety as exemplified by the tetrasaccharide, sialyl Lewis X (sLeX). An important property of the selectin‐sLeX interaction is its ability to withstand the hydrodynamic force of the blood flow. Herein, we used single‐molecule dynamic force spectroscopy (DFS) to identify the molecular determinants within sLeX that give rise to the dynamic properties of the selectin/sLeX interaction. Our atomic force microscopy (AFM) measurements revealed that the unbinding of the selectin/sLeX complexes involves overcoming at least two activation barriers. The inner barrier, which determines the dynamic response of the complex at high forces, is governed by the interaction between the Fuc residue of sLeX and a Ca2+ ion chelated to the lectin domain of the selectin molecule, whereas the outer activation barrier can be attributed to interactions involving the sialic acid residue of sLeX. Due to their steep inner activation barriers, the selectin‐sLeX complexes are less sensitive to high pulling forces. Hence, besides its contribution to the bond energy, the Ca2+ ion also grants the selectin–sLeX complexes a tensile strength that is crucial for the selectin‐mediated rolling of leukocytes.
The Gas‐Phase Hydrogen Bond Complexes between Formic Acid with Hydroxyl Radical: A Theoretical Study
Authors: Torrent‐Sucarrat Miquel , Anglada Josep M. 
Published: February 2004

AbstractWe report a theoretical study on seven radical hydrogen bond complexes between syn‐HCOOH and OH and eight radical hydrogen bond complexes between anti‐HCOOH and OH, that have been carried out by using the B3 LYP, MP2, QCISD, and CCSD(T) theoretical approaches with the 6‐311+G(2df,2p) basis set. In all cases, the bonding features were analysed using the atoms in molecules (AIM) theory by Bader and the natural bond orbital (NBO) partition scheme by Weinhold et al. We have found twelve complexes having a single hydrogen bond and three complexes presenting a cyclic structure with multiple bonds, pointing out the existence of a cooperative effect. One of them presents a bound O⋅⋅⋅O interaction producing a stabilisation effect. The stability of these complexes has been calculated to be in the −0.81 and −5.96 kcal mol−1range and their possible implication in the HCOOH plus OH reaction is also discussed. Finally, we also report the computed harmonic vibrational frequencies of the two OH stretching modes and the HOC out‐of‐plane wagging mode, along with the frequency red‐shifts originated by the complex formation and the corresponding computed intensity ratio relative to the monomers.
Visualization of Atomic Processes on Ruthenium Dioxide using Scanning Tunneling Microscopy
Authors: Over H. , Knapp M. , Lundgren E. , Seitsonen A. P. , Schmid M. , Varga P. 
Published: February 2004

AbstractThe visualization of surface reactions on the atomic scale provides direct insight into the microscopic reaction steps taking place in a catalytic reaction at a (model) catalyst's surface. Employing the technique of scanning tunneling microscopy (STM), we investigated the CO oxidation reaction over the RuO2(110) and RuO2(100) surfaces. For both surfaces the protruding bridging O atoms are imaged in STM as bright features. The reaction mechanism is identical on both orientations of RuO2. CO molecules adsorb on the undercoordinated surface Ru atoms from where they recombine with undercoordinated O atoms to form CO2 at the oxide surface. In contrast to the RuO2(110) surface, the RuO2(100) surface stabilizes also a catalytically inactive c(2×2) surface phase onto which CO is not able to adsorb above 100 K. We argue that this inactive RuO2(100)‐c(2×2) phase may play an important role in the deactivation of RuO2 catalysts in the electrochemical Cl2 evolution and other heterogeneous reactions.
Manganese, Iron, Cobalt, and Nickel Oxo‐, Peroxo‐, and Superoxoclusters: A Density Functional Theory Study
Authors: Uzunova Ellie L. , Nikolov Georgi St. , Mikosch Hans 
Published: February 2004

AbstractThe 3d‐transition‐metal dioxo‐, peroxo‐, and superoxoclusters with the general composition MO2, M(O2), and MOO (M=Mn, Fe, Co, and Ni) were studied by DFT by the B1LYP functional. The dioxides in their ground states represent the global minima for the M+O2 system. Both ground‐state dioxides and the lowest‐energy peroxides are in their (d‐only) highest spin states. The 6A1 state of Co(O2) exceeds the d‐only spin‐multiplicity value (quartet), being nearly isoenergetic with the 4A1 state of Co(O2). The energy gain on transforming the peroxides to the corresponding dioxides decreases in the order Mn(O2)>Fe(O2)>Co(O2)>Ni(O2) and varies in the range 0.27–1.8 eV. The dissociation energy to M+O2 for all studied peroxides is less than 1 eV being the lowest (0.47 eV) for Mn(O2). The Mn and Fe peroxides need less than 0.3 eV to rupture one of the MO bonds to form the corresponding superoxide. Mn and Fe superoxides are less stable than the corresponding peroxides; the superoxide of Co is more stable than its peroxide, while Ni superoxide is unstable—its energy is above the limit of dissociation to Ni+O2. According to the electrostatic potential maps, the oxygen atoms in the peroxides are more nucleophilic than those in the dioxides and superoxides, in which the terminal oxygen atom is more nucleophilic than the M‐bonded oxygen atom. This result differs from the expectations based on charge‐distribution analysis.
Improper Hydrogen CH⋅⋅⋅O Bonds Cause Self‐Association of α,β‐Enaminoketones Containing Fluorosubstituted Alkyl Groups
Authors: Wójcik Jacek , Kamienska‐Trela Krystyna , Pecul Magdalena , Bartoszak‐Adamska Elzbieta , Vdovienko Siergiej I. , Gerus Igor I. 
Published: February 2004

AbstractConcentration‐ and temperature‐dependent IR, NMR and dipole‐moment studies on 4‐N,N‐dimethylamino‐1,1,1‐trifluoro‐3‐buten‐2‐one and two of its higher homologues showed that these compounds undergo reversible dimerization in nonpolar solvents. Antiparallel “closed” dimers are formed with a network of improper intermolecular CH⋅⋅⋅O hydrogen bonds. Quantitative analysis of the 1H NMR data yielded ΔH0=−17.6 kJ mol−1 and ΔS0=‐46.9 J deg−1 mol−1. The interactions observed are the strongest among those involving a CH group reported so far. The complex described here is the first example of a cyclic complex stabilized by two improper CH⋅⋅⋅O hydrogen bonds. The conclusions drawn from the solution and solid‐state data were confirmed by ab initio calculations.
Stability condition and steady‐state solution of various α–β filters for linear FM pulse compression radars
Authors: Amishima Takeshi , Ito Masayoshi , Kosuge Yoshio 
Published: February 2004

AbstractPulse compression is often used in radar to increase the detection range while suppressing the peak transmission power and to prevent a drop in the range resolution. However, a drawback of this technique is the target range is observed offset by an amount proportional to the range rate of the target. On the other hand, various α–β filters have been derived based on the differences in motion models. These filters define the process noise in a discrete system in terms of the velocity, the acceleration, or the n‐th derivative of the acceleration, or discretized after defining the process noise in a continuous system in terms of the acceleration. For the process noise in a discrete system defined in terms of the acceleration, we propose an α–β filter that tracks while internally correcting the bias observation error described above. In this paper, we show a necessary and sufficient stability condition of various stable α–β filters that track while internally correcting the bias observation error. We show that the stable gain region does not depend on the Doppler shift time constant and is invariant. Then we formulate the relationship between α and β and the error covariance matrix. In addition, for α–β filters where the process noise in a discrete system is defined in terms of the velocity or the acceleration, or where the process noise in a continuous system is defined in terms of the acceleration and then discretized, we showed that, in practice, the α–β filter with the process noise defined in terms of the velocity in discrete time, has superior performance, when the performance is measured in terms of error covariance matrix given a fixed maneuver index. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(6): 13–22, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10134
Detecting changes of buildings using stereo matching from aerial images taken at different positions and times
Authors: Watanabe Shintaro , Miyajima Koji , Inoue Ushio , Nakamura Taichi 
Published: February 2004

AbstractGIS base maps are updated by using parallax to compare two aerial images taken at different times to interpret structural changes. Since an aerial image generally photographs a wide range, this interpretation work requires a great deal of time. Therefore, in this paper, the authors propose a method of automatically extracting structural changes with high precision to reduce the load of this interpretation work. Not only do the times differ at which the aerial images used for comparison were taken, but the shooting positions also frequently differ. This causes differences in shadow shapes and differences in structure viewing methods, and when aerial images are compared during automatic interpretation, it will cause the detection precision of structural changes to decrease. To deal with this problem, the authors eliminated the effects of differences in structure viewing methods by applying stereo matching and letting noncorresponding regions be structural change candidates. In addition, to correctly detect structural changes from those candidates, the authors used the outdoor light source model, which had been proposed by previous authors, to eliminate the effects of differences in shadow shapes. The results that were obtained by the proposed method showed that the detection precision of structural changes was approximately four times that of the conventional method. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(6): 55–65, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20084
Surface receptors identify mouse NK1.1+ T cell subsets distinguished by function and T cell receptor type
Authors: Stenström Martin , Sköld Markus , Ericsson Anna , Beaudoin Lucie , Sidobre Stephane , Kronenberg Mitchell , Lehuen Agnès , Cardell Susanna 
Published: February 2004

AbstractNatural killer T (NKT) lymphocytes rapidly produce several cytokines, including IL‐4 and IFN‐γ, upon activation, and act as regulatory cells at an early interphase of innate and adaptive immune responses. They have been implicated as important elements in diverse immune responses including the regulation of autoimmune disease, the immune response to infections, and the prevention of tumor metastasis. The broad spectrum of their activities suggested that functionally different subsets of NKT cells may exist. We demonstrate two functionally distinct splenic NKT populations identified by the expression of CD49b and CD69, respectively. Each NKT subset was represented by the amplified transgenic NKT cell population in a distinct transgenic mouse line expressing a CD1d‐restricted TCR. CD49bhigh CD69– NKT cells, termed NKT1 cells by us, were high producers of IFN‐γ after stimulation, but essentially devoid of IL‐4‐synthesizing cells. Most NKT1 cells used diverse (non‐Vα14‐canonical) TCR. The CD69+ CD49–/low NKT cell population, which we term NKT2, produced large quantities of IL‐4 and substantial amounts of IFN‐γ upon activation and were dominated by cells using the canonical Vα14‐Jα18 T cell receptor. Knowledge of the unique roles of the different NKT cell subsets in specific situations will be essential for our understanding of NKT cell biology.
Characterization of three CpG oligodeoxynucleotide classes with distinct immunostimulatory activities
Authors: Vollmer Jörg , Weeratna Risini , Payette Paul , Jurk Marion , Schetter Christian , Laucht Meike , Wader Tanja , Tluk Sibylle , Liu Ming , Davis Heather L. , Krieg Arthur M. 
Published: February 2004

AbstractOligodeoxynucleotides (ODN) with unmethylated deoxycytidyl‐deoxyguanosine (CpG) dinucleotides (CpG ODN) mimic the immunostimulatory activity of bacterial DNA and are recognized by the Toll‐like receptor 9 (TLR9). CpG ODN of the B‐Class stimulate strong B cell and NK cell activation and cytokine production. The highest degrees of NK stimulation as well as IFN‐α secretion by plasmacytoid DC were found to occur only with A‐Class ODN. A third class of CpG ODN combines the immune effects of A‐ and B‐Class CpG ODN. C‐Class ODN strongly stimulate B cell or NK cell activation and IFN‐α production. In contrast to the A‐Class, the C‐Class is wholly phosphorothioate, has no poly‐G stretches, but has palindromic sequences combined with stimulatory CpG motifs. All classes stimulate TLR9‐dependent signaling, but with strikingly different dose‐response relationships that are quite in contrast to those observed for IFN‐α. Effects similar to those on human cells were observed on mouse splenocytes. In contrast, splenocytes from TLR9‐deficient mice did not show any response to the three CpG ODN classes. In vivo studies demonstrate that C‐Class ODN are very potent Th1adjuvants. C‐Class ODN may represent new therapeutic drugs that combine the effects of A‐ and B‐Class ODN for broad applications in infectious disease or cancer therapy.
Cyclopentenone prostaglandins induce endothelial cell apoptosis independent of the peroxisome proliferator‐activated receptor‐γ
Authors: Erl Wolfgang , Weber Christian , Zernecke Alma , Neuzil Jiri , Vosseler Claudia A. , Kim Hyo Jung , Weber Peter C. 
Published: February 2004

AbstractCyclopentenone prostaglandins (CP‐PG), such as prostaglandin A1 (PGA1) or 15‐deoxy‐Δ12,14‐prostaglandin J2 (PGJ2), induce apoptosis in different cell types. PGJ2 is also a potent activator of the peroxisome proliferator‐activated receptor‐γ (PPARγ). We investigated whether PPARγ regulates CP‐PG‐induced apoptosis in endothelial cells (EC). We show that CP‐PG induce apoptosis in human umbilical vein EC (HUVEC). Incubation with PGA1 or PGJ2 for 24 h reduced HUVEC number and viability, while the synthetic activators Wy14643 or rosiglitazone had no effect. Flow cytometry and cell cycle analysis revealed externalized phosphatidylserine, caspase‐3 activation, and an increased percentage of cellswith a reduced DNA content by CP‐PG treatment. EMSA demonstrated an activation of PPARγ by PGJ2 and rosiglitazone. Immunohistochemistry of HUVEC and immunoblot analyses of protein extracts showed that PPARγ was localized in the nuclei of HUVEC, and that CP‐PG treatment decreased the amount of PPARγ protein. This degradation was prevented by a pan‐caspase inhibitor. Treatment of differentiated, endothelial‐like PPARγ‐deficient stem cells, or of HUVEC transfected with dominant‐negative PPARγ with CP‐PG, induced cell death and apoptosis. Our findings show that PGA1 and PGJ2 induce apoptosis in endothelial cells independent of PPARγ. As the synthesis of PGJ2 is increased at sites of inflammation, our results may suggest a possiblemechanism for endothelial damage.
FcγRII expression on follicular dendritic cells and immunoreceptor tyrosine‐based inhibition motif signaling in B cells
Authors: Aydar Yüksel , Wu Jiuhua , Song Jingmei , Szakal Andras K. , Tew John G. 
Published: February 2004

AbstractImmune complexes (IC) initiate immunoreceptor tyrosine‐based inhibition motif (ITIM) signaling and inhibit B cell activation by coligating B cell receptor for antigen (BCR) and FcγRII. Nevertheless, IC on follicular dendritic cells (FDC) stimulate rapid germinal center (GC) B cell proliferation suggesting that interactions between IC and FDC render IC capable of B cell activation. Tounderstand this, we studied the kinetics of FDC FcγRII and complement receptors 1 and 2 (CR1&2) expressions during the GC reaction and determined whether FDC FcγRII could bind Fc in IC and block ITIM signaling. Mice were immunized with sheep red blood cells (SRBC), and CR1&2 and FcγRII levels in FDC reticula were monitored. The role of FDC FcγRII was studied using anti‐BCR‐stimulated A20 cells. Levels of FDC FcγRII in spleens of SRBC‐injected mice increased within 24 h and were dramatically increased (∼50‐fold) on days 3 and 5. In contrast, CR1&2 levels increased less than twofold. Addition of normal FDC, but not FDC lacking FcγRII, reduced and reversed anti‐BCR‐induced SH2 domain‐containing inositol phosphatase (SHIP)‐1 phosphorylation in A20 cells. FDC wereable to induce normal recall responses even after overnight incubation of the lymphocytes with IC to stimulate ITIM signaling. Engagement of Ig Fc with numerous FcγRII on FDC appears to minimize IC‐induced ITIM signaling. Thus, rapid up‐regulation of FDC FcγRII may explain why poorly immunogenic IC are rendered highly immunogenic when presented by FDC in GC.
Identification of a novel thioredoxin‐related protein, PC‐TRP, which is preferentially expressed in plasma cells
Authors: Wrammert Jens , Källberg Eva , Leanderson Tomas 
Published: February 2004

AbstractUsing cDNA subtraction we have identified a previously unknown cDNA, termed plasma cell thioredoxin‐related protein (PC‐TRP), which was overexpressed in plasma cells in vitro. The full‐length 2636‐bp PC‐TRP cDNA contained an open reading frame coding for 417 amino acids. The cDNA sequence was mapped to a region on mouse chromosome 13 and the PC‐TRP gene consists of ten exons distributed over a 28‐kb region. The PC‐TRP was found to contain three atypical thioredoxin domains and showed functional thioredoxin activity in vitro. A more detailed analysis revealed that PC‐TRP was expressed at a high level in plasma cells, both at the mRNA and protein level, while present at very low levels in all other cells and tissues examined. Immunohistological analysis revealed that PC‐TRP was expressed at high levels in all plasma cells isolated from bone marrow or lamina propria, irrespective of their Ig isotype. In the spleen, however, 60% of the IgG‐expressing plasma cells showed only a dull staining at day 14 after immunization, while >90% of the IgG‐secreting cells in the spleen expressed PC‐TRP at day 21 after immunization. In addition, an IgG‐secreting, PC‐TRPdull plasma cell population could also be observed after B cell activation in vitro.