bluuebunny/crossref_metadata_2025 huggingface dataset:
Torque-Dependent Compliance Control in the Joint Space for Robot-Mediated Motor Therapy
Authors: Formica Domenico , Zollo Loredana , Guglielmelli Eugenio
Published: March 2006

This paper is focused on the design of interaction control of robotic machines for rehabilitative motor therapy of the upper limb. The control approach tries to address requirements deriving from the application field and adopts a bioinspired approach for regulating robot behavior in the interaction with the patient. An inner-outer loop control scheme is proposed. In order to tune the level of force and improve robot adaptability in the interaction with the patient, a classical outer force control loop is used. For the inner loop, a novel control law for low-level tuning of robot compliance is introduced, that is borrowed from studies on the biological mechanisms for regulating the elastic properties of the human arm. A dedicated simulation tool, which models the dynamics of an operational robotic machine interacting with a human subject, has been developed. Validation of basic adaptability and safety requirements of the control scheme is carried out in simple tasks, e.g., reaching and contact/noncontact transitions, as well as in simulated situations of typical motor exercises. In particular, the simulation tests demonstrate the adaptive capabilities of the proposed control schemes, e.g., in counterbalancing patient incorrect movements related to the various levels of disability. Moreover, preliminar experimental tests carried out on a real robotic system demonstrated the possibility of using the proposed approach for guaranteeing safe interaction with the patient.
The Last Deglaciation of the Southeastern Sector of the Scandinavian Ice Sheet
Authors: Rinterknecht V. R. , Clark P. U. , Raisbeck G. M. , Yiou F. , Bitinas A. , Brook E. J. , Marks L. , Zelčs V. , Lunkka J.-P. , Pavlovskaya I. E. , Piotrowski J. A. , Raukas A.
Published: March 2006

The Scandinavian Ice Sheet (SIS) was an important component of the global ice sheet system during the last glaciation, but the timing of its growth to or retreat from its maximum extent remains poorly known. We used 115 cosmogenic beryllium-10 ages and 70 radiocarbon ages to constrain the timing of three substantial ice-margin fluctuations of the SIS between 25,000 and 12,000 years before the present. The age of initial deglaciation indicates that the SIS may have contributed to an abrupt rise in global sea level. Subsequent ice-margin fluctuations identify opposite mass-balance responses to North Atlantic climate change, indicating differing ice-sheet sensitivities to mean climate state.
The Interaction of the Atmosphere of Enceladus with Saturn's Plasma
Authors: Tokar R. L. , Johnson R. E. , Hill T. W. , Pontius D. H. , Kurth W. S. , Crary F. J. , Young D. T. , Thomsen M. F. , Reisenfeld D. B. , Coates A. J. , Lewis G. R. , Sittler E. C. , Gurnett D. A.
Published: March 2006

During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 × 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 × 10
27
H
2
O molecules per second) is inferred.
Observation of Feshbach Resonances in the F + H
2
→ HF + H Reaction
Authors: Qiu Minghui , Ren Zefeng , Che Li , Dai Dongxu , Harich Steve A. , Wang Xiuyan , Yang Xueming , Xu Chuanxiu , Xie Daiqian , Gustafsson Magnus , Skodje Rex T. , Sun Zhigang , Zhang Dong H.
Published: March 2006

Reaction resonances, or transiently stabilized transition-state structures, have proven highly challenging to capture experimentally. Here, we used the highly sensitive H atom Rydberg tagging time-of-flight method to conduct a crossed molecular beam scattering study of the F + H
2
→ HF + H reaction with full quantum-state resolution. Pronounced forward-scattered HF products in the
v
′ = 2 vibrational state were clearly observed at a collision energy of 0.52 kcal/mol; this was attributed to both the ground and the first excited Feshbach resonances trapped in the peculiar HF(
v
′ = 3)-H′ vibrationally adiabatic potential, with substantial enhancement by constructive interference between the two resonances.
Combinatorial Effects of Odorant Mixes in Olfactory Cortex
Authors: Zou Zhihua , Buck Linda B.
Published: March 2006

In mammals, each odorant is detected by a combination of different odorant receptors. Signals from different types of receptors are segregated in the nose and the olfactory bulb, but appear to be combined in individual neurons in the olfactory cortex. Here, we report that binary odorant mixes stimulate cortical neurons that are not stimulated by their individual component odorants. We propose that cortical neurons require combinations of receptor inputs for activation and that merging the receptor codes of two odorants provides novel combinations of receptor inputs that stimulate neurons beyond those activated by the single odorants. These findings may explain why odorant mixtures can elicit novel odor percepts in humans.
The Avian Coronavirus Infectious Bronchitis Virus Undergoes Direct Low-pH-Dependent Fusion Activation during Entry into Host Cells
Authors: Chu Victor C. , McElroy Lisa J. , Chu Vicky , Bauman Beverley E. , Whittaker Gary R.
Published: March 2006

Coronaviruses are the causative agents of respiratory disease in humans and animals, including severe acute respiratory syndrome. Fusion of coronaviruses is generally thought to occur at neutral pH, although there is also evidence for a role of acidic endosomes during entry of a variety of coronaviruses. Therefore, the molecular basis of coronavirus fusion during entry into host cells remains incompletely defined. Here, we examined coronavirus-cell fusion and entry employing the avian coronavirus infectious bronchitis virus (IBV). Virus entry into cells was inhibited by acidotropic bases and by other inhibitors of pH-dependent endocytosis. We carried out fluorescence-dequenching fusion assays of R18-labeled virions and show that for IBV, coronavirus-cell fusion occurs in a low-pH-dependent manner, with a half-maximal rate of fusion occurring at pH 5.5. Fusion was reduced, but still occurred, at lower temperatures (20°C). We observed no effect of inhibitors of endosomal proteases on the fusion event. These data are the first direct measure of virus-cell fusion for any coronavirus and demonstrate that the coronavirus IBV employs a direct, low-pH-dependent virus-cell fusion activation reaction. We further show that IBV was not inactivated, and fusion was unaffected, by prior exposure to pH 5.0 buffer. Virions also showed evidence of reversible conformational changes in their surface proteins, indicating that aspects of the fusion reaction may be reversible in nature.
Plasmid DNA Sequences Present in Conventional Herpes Simplex Virus Amplicon Vectors Cause Rapid Transgene Silencing by Forming Inactive Chromatin
Authors: Suzuki Masataka , Kasai Kazue , Saeki Yoshinaga
Published: March 2006

The herpes simplex virus (HSV)-based amplicon vector, a bacterial-viral-mammalian cell shuttle system, holds promise as a versatile gene delivery vehicle because of its large transgene capacity. However, amplicon-mediated transgene expression is often transient. We hypothesized that the presence of prokaryotic DNA sequences within the packaged vector genome can trigger transcriptional silencing of the entire vector sequence. To test this, we constructed a novel amplicon vector devoid of bacterial sequences (minicircle [MC] amplicon). Although the same dose of the minicircle amplicon vector in normal human fibroblasts resulted in an expression of luciferase approximately 20 times higher than that caused by the conventional amplicon vector, no significant difference was observed in copy numbers of luciferase DNA between MC amplicon- and control-transduced cells. Quantitative analyses of levels of luciferase mRNA revealed that differential expression of luciferase was controlled at the transcriptional level. Chromatin immunoprecipitation PCR analyses of several regions of vector genomes revealed that the bacterial sequences found in the conventional amplicon DNA were associated with an inactive form of chromatin immediately after infection. The presence of bacterial sequences also affected the remaining vector sequences in the conventional amplicon vector. Finally, nude mice injected with the MC amplicon exhibited higher and more sustained expression of luciferase than those injected with the conventional amplicon, confirming the usefulness of the MC amplicon devoid of bacterial sequences. Although additional improvements are absolutely required, these findings are a significant first step toward developing a novel HSV amplicon vector that can achieve enhanced long-term transgene expression.
Analyses of Subgenomic Promoters of
Hibiscus Chlorotic Ringspot Virus
and Demonstration of 5′ Untranslated Region and 3′-Terminal Sequences Functioning as Subgenomic Promoters
Authors: Li Weimin , Wong Sek-Man
Published: March 2006

Hibiscus chlorotic ringspot virus
(HCRSV), which belongs to the genus
Carmovirus
, generates two 3′-coterminal subgenomic RNAs (sgRNAs) of 1.4 kb and 1.7 kb. Transcription start sites of the two sgRNAs were identified at nucleotides (nt) 2178 and 2438, respectively. The full promoter of sgRNA1, a 118-base sequence, is localized between positions +6 and −112 relative to its transcription start site (+1). Similarly, a 132-base sequence, from +6 to −126, defines the sgRNA2 promoter. Computer analysis revealed that both sgRNA promoters share a similar two-stem-loop (SL1 + SL2) structure, immediately upstream of the transcription start site. Mutational analysis of the primary sequence and secondary structures showed further similarities between the two subgenomic promoters. The basal portion of SL2, encompassing the transcription start site, was essential for transcription activity in each promoter, while SL1 and the upper portion of SL2 played a role in transcription enhancement. Both the 5′ untranslated region (UTR) and the last 87 nt at the 3′ UTR of HCRSV genomic RNA are likely to be the putative genomic plus-strand and minus-strand promoters, respectively. They function well as individual sgRNA promoters to produce ectopic subgenomic RNAs in vivo but not to the same levels of the actual sgRNA promoters. This suggests that HCRSV sgRNA promoters share common features with the promoters for genomic plus-strand and minus-strand RNA synthesis. To our knowledge, this is the first demonstration that both the 5′ UTR and part of the 3′ UTR can be duplicated and function as sgRNA promoters within a single viral genome.
A Simian Virus 5 (SV5) P/V Mutant Is Less Cytopathic than Wild-Type SV5 in Human Dendritic Cells and Is a More Effective Activator of Dendritic Cell Maturation and Function
Authors: Arimilli Subhashini , Alexander-Miller Martha A. , Parks Griffith D.
Published: March 2006

Human epithelial cells infected with the parainfluenza virus simian virus 5 (SV5) show minimal activation of host cell interferon (IFN), cytokine, and cell death pathways. In contrast, a recombinant SV5 P/V gene mutant (rSV5-P/V-CPI−) overexpresses viral gene products and is a potent inducer of IFN, proinflammatory cytokines, and apoptosis in these cells. In this study, we have compared the outcomes of wild-type (WT) SV5 and rSV5-P/V-CPI−infections of primary human dendritic cells (DC), important antigen-presenting cells for initiating adaptive immune responses. We have tested the hypothesis that a P/V mutant which activates host antiviral responses will be a more potent inducer of DC maturation and function than WT rSV5, which suppresses host cell responses. Infection of peripheral blood mononuclear cell-derived immature DC with WT rSV5 resulted in high levels of viral protein and progeny virus but very little increase in cell surface costimulatory molecules or secretion of IFN and proinflammatory cytokines. In contrast, immature DC infected with the rSV5-P/V-CPI−mutant produced only low levels of viral protein and progeny virus, but these infected cells were induced to secrete IFN-α and other cytokines and showed elevated levels of maturation markers. Unexpectedly, DC infected with WT rSV5 showed extensive cytopathic effects and increased levels of active caspase-3, while infection of DC with the P/V mutant was largely noncytopathic. In mixed-culture assays, WT rSV5-infected DC were impaired in the ability to stimulate proliferation of autologous CD4+T cells, whereas DC infected with the P/V mutant were very effective at activating T-cell proliferation. The addition of a pancaspase inhibitor to DC infected with WT rSV5 reduced cytopathic effects and resulted in higher surface expression levels of maturation markers. Our finding that the SV5 P/V mutant has both a reduced cytopathic effect in human DC compared to WT SV5 and an enhanced ability to induce DC function has implications for the rational design of novel recombinant paramyxovirus vectors based on engineered mutations in the viral P/V gene.
Tumor Necrosis Factor Alpha Enhances Influenza A Virus-Induced Expression of Antiviral Cytokines by Activating RIG-I Gene Expression
Authors: Matikainen Sampsa , Sirén Jukka , Tissari Jorma , Veckman Ville , Pirhonen Jaana , Severa Martina , Sun Qiang , Lin Rongtuan , Meri Seppo , Uzé Gilles , Hiscott John , Julkunen Ilkka
Published: March 2006

Epithelial cells of the lung are the primary targets for respiratory viruses. Virus-carried single-stranded RNA (ssRNA) can activate Toll-like receptors (TLRs) 7 and 8, whereas dsRNA is bound by TLR3 and a cytoplasmic RNA helicase, retinoic acid-inducible protein I (RIG-I). This recognition leads to the activation of host cell cytokine gene expression. Here we have studied the regulation of influenza A and Sendai virus-induced alpha interferon (IFN-α), IFN-β, interleukin-28 (IL-28), and IL-29 gene expression in human lung A549 epithelial cells. Sendai virus infection readily activated the expression of the IFN-α, IFN-β, IL-28, and IL-29 genes, whereas influenza A virus-induced activation of these genes was mainly dependent on pretreatment of A549 cells with IFN-α or tumor necrosis factor alpha (TNF-α). IFN-α and TNF-α induced the expression of the RIG-I, TLR3, MyD88, TRIF, and IRF7 genes, whereas no detectable TLR7 and TLR8 was seen in A549 cells. TNF-α also strongly enhanced IKKε mRNA and protein expression. Ectopic expression of a constitutively active form of RIG-I (ΔRIG-I) or IKKε, but not that of TLR3, enhanced the expression of the IFN-β, IL-28, and IL-29 genes. Furthermore, a dominant-negative form of RIG-I inhibited influenza A virus-induced IFN-β promoter activity in TNF-α-pretreated cells. In conclusion, IFN-α and TNF-α enhanced the expression of the components of TLR and RIG-I signaling pathways, but RIG-I was identified as the central regulator of influenza A virus-induced expression of antiviral cytokines in human lung epithelial cells.
Role of the Human T-Cell Leukemia Virus Type 1 PTAP Motif in Gag Targeting and Particle Release
Authors: Dorweiler Irene J. , Ruone Susan J. , Wang Huating , Burry Richard W. , Mansky Louis M.
Published: March 2006

Human T-cell leukemia virus type 1 (HTLV-1) Gag is targeted to the plasma membrane for particle assembly and release. How HTLV-1 Gag targeting occurs is not well understood. The PPPY and PTAP motifs were previously shown to be involved in HTLV-1 particle release with PTAP playing a more subtle role in virus budding. These L domains function through the interaction with host cellular proteins normally involved in multivesicular body (MVB) morphogenesis. The plasma membrane pathway rather than the MVB pathway was found to be the primary pathway for HTLV-1 particle release in HeLa cells. Intriguingly, disruption of the PTAP motif led to a defect in the targeting of Gag from the plasma membrane to CD63-positive MVBs. Particles or particle buds were observed to be associated with MVBs by electron microscopy, implying that Gag targeting to the MVB resulted in particle budding. Blocking clathrin-dependent endocytosis was found not to influence localization of the HTLV-1 Gag PTAP mutant, indicating that Gag did not reach the MVBs through clathrin-dependent endocytosis. Our observations imply that the interaction between Gag and TSG101 is not required for Gag targeting to the MVB. Overexpression of dynamitin p50 increased particle release, suggesting that there was an increase in the intracellular transport of MVBs to the cell periphery by the utilization of the dynein-dynactin motor complex. Intriguingly, virus particle release with this mutant was reduced by 20-fold compared to that of wild type in HeLa cells, which is in marked contrast to the less-than-twofold defect observed for particle production of the HTLV-1 Gag PTAP mutant from 293T cells. These results indicate that the role of the PTAP motif in L domain function is cell type dependent.
Impact of the Interaction between Herpes Simplex Virus Type 1 Regulatory Protein ICP0 and Ubiquitin-Specific Protease USP7 on Activation of Adeno-Associated Virus Type 2
rep
Gene Expression
Authors: Geoffroy Marie-Claude , Chadeuf Gilliane , Orr Anne , Salvetti Anna , Everett Roger D.
Published: March 2006

Expression of the herpes simplex virus type 1 (HSV-1) regulatory protein ICP0 in transfected cells reactivates
rep
gene expression from integrated adeno-associated virus (AAV) type 2 genomes via a mechanism that requires both its RING finger and USP7 interaction domains. In this study, we found that the
rep
reactivation defect of USP7-binding-negative ICP0 mutants can be overcome by further deletion of sequences in the C-terminal domain of ICP0, indicating that binding of USP7 to ICP0 is not directly required. Unlike the case in transfected cells, only the RING finger domain of ICP0 was essential for
rep
gene reactivation during HSV-1 infection. However, mutants unable to bind to USP7 activate HSV-1 gene expression and reactivate
rep
gene expression with reduced efficiencies. These results further elucidate the role of ICP0 as a helper factor for AAV replication and illustrate that care is required when extrapolating from the properties of ICP0 in transfection assays to events occurring during HSV-1 infection.
Recovery of a Neurovirulent Human Coronavirus OC43 from an Infectious cDNA Clone
Authors: St-Jean Julien R. , Desforges Marc , Almazán Fernando , Jacomy Hélène , Enjuanes Luis , Talbot Pierre J.
Published: March 2006

This study describes the assembly of a full-length cDNA clone of human coronavirus (HCoV)-OC43 in a bacterial artificial chromosome (BAC). The BAC containing the full-length infectious cDNA (pBAC-OC43
FL
) was assembled using a two-part strategy. The first step consisted in the introduction of each end of the viral genome into the BAC with accessory sequences allowing proper transcription. The second step consisted in the insertion of the whole HCoV-OC43 cDNA genome into the BAC. To produce recombinant viral particles, pBAC-OC43
FL
was transfected into BHK-21 cells. Recombinant virus displayed the same phenotypic properties as the wild-type virus, including infectious virus titers produced in cell culture and neurovirulence in mice.
Comparison of the Mutation Rates of Human Influenza A and B Viruses
Authors: Nobusawa Eri , Sato Katsuhiko
Published: March 2006

Human influenza A viruses evolve more rapidly than influenza B viruses. To clarify the cause of this difference, we have evaluated the mutation rate of the nonstructural gene as revealed by the genetic diversity observed during the growth of individual plaques in MDCK cells. Six plaques were studied, representing two strains each of type A and B viruses. A total of 813,663 nucleotides were sequenced, giving rates of 2.0 × 10
−6
and 0.6 × 10
−6
mutations per site per infectious cycle, which, when extended to 1 year, agree well with the published annual evolutionary rates.
A study of the isomerization and dissociation of formal [acetonemethanol]+· ionmolecule complexes
Authors: Wang Xian , Holmes John L
Published: March 2006

The energy barrier for the ketoenol isomerization of the isolated acetone ion to its distonic (enol) isomer lies above its lowest dissociation limit and so the spontaneous isomerization can never be observed. Ketoenol isomerizations can be catalyzed within appropriate ionmolecule complexes. The present study involved two systems, [(CH3)2C=O···H+···O(H)CH2·] (ion 1) and [(CH3)2C=O···H+····OCH3] (ion 2), in both stable and metastable adducts. When acetone is bound to ·CH2OH though a proton bridge, shown as ion 1, an enol acetone ion is produced. This reaction results from a proton attaching to the acetone, which then gives an H· atom back to the radical site by a 1,6-H transfer, involving a transition state of low energy requirement. In contrast, when the acetone is protonated and bound to the radical CH3O· (ion 2), the above rearrangement does not take place. The metastable complex ion 2 loses a methyl radical, producing a new [C3H7O2]+ isomer of structure [CH3C+(O)···(H)OCH3]. Tandem mass spectrometry combined with ab initio calculations were used to investigate the two systems. Potential energy surface diagrams were obtained by calculations at the MP2/6-31+G(d) level of theory to aid further elucidation of the reaction mechanisms. Key words: ionmolecule complexes, ketoenol mechanisms, ion rearrangements and structures.
Gas-phase experiments on the chemistry and coordination of Zn(II) by aprotic solvent molecules
Authors: Duncombe Bridgette J , Pukar Lijlijana , Wu Bohan , Stace Anthony J
Published: March 2006

Experiments have been performed in the gas phase on a series of doubly charged zincligand complexes to elucidate their solvation structure and available fragmentation pathways. Production of such complexes was achieved by the formation of neutral argonligand clusters followed by the subsequent addition of a single zinc atom using a pickup technique. Multiply charged ions were then produced by electron impact within a high resolution, double-focusing mass spectrometer. Studies have been undertaken on a number of zinc(II)  aprotic solvent complexes including those consisting of argon and carbon dioxide in association with the zinc cation. Investigation of these novel metalsolvent clusters took the form of recorded parent ion intensity distributions and the measurement of fragmentation patterns promoted via collision-induced dissociation (CID). Discussion of the intensity distributions is presented in terms of the solvation of Zn(II) by each solvent, drawing on existing theoretical and experimental data from the gaseous and condensed phases. Investigation of collision-induced dissociation processes includes identifying charge transfer reactions in each solvated system, and analysis of the results in terms of kinetic energy release as well as possible mechanisms for fragmentation pathways. Key words: zinc, clusters, dications, gas phase, solvation.
An investigation of the ionmolecule interactions of protonated glycine with ammonia by high pressure mass spectrometry and ab initio calculations
Authors: Wu Ronghu , McMahon Terry B
Published: March 2006

The thermochemistry of gas-phase ion molecule interactions and the structures of various clusters between protonated glycine (GlyH+), glycine, and ammonia have been studied by high pressure mass spectrometry (HP-MS) and ab initio calculations. For the association reactions of GlyH+ with NH3, Gly(NH3)H+ with NH3, and (Gly)2H+ with NH3, the enthalpy changes experimentally determined are 23.2, 18.3, and 19.1 kcal mol1 (1 cal = 4.184 J), respectively. For all clusters investigated, the measured binding enthalpies are in excellent agreement with those obtained from ab initio calculations at the B3LYP/6-311+G(d,p) level of theory. Different isomers of each of these clusters have been obtained and the corresponding binding energies have been computed. The potential energy surface for isomerization of the clusters of protonated glycine with ammonia has also been computed at the same level. For this cluster, the three most stable isomers all involve a proton transfer from protonated glycine to ammonia. According to the calculated potential energy surface, the barrier between GN4, the least stable isomer, and the most stable isomer (GN1) is 11.5 kcal mol1 at 298 K. Thus, this isomerization will be facile given the exothermicity of the association reaction. Therefore, a statistical distribution of isomers will be present under thermal equilibrium conditions. Single point energy calculations at the MP2(full)/6-311++G(2d,2p)//B3LYP/6-311+G(d,p) level of theory reveal that the isomer GN2 in which glycine has a zwitterionic structure has the same energy as the most stable non-zwitterionic isomer GN1. NH4+ evidently may stabilize the zwitterionic structure of glycine. In contrast, N2H7+ and GlyH+ are not as effective in stabilizing the zwitterionic structure of glycine. This likely results from the more localized charge in NH4+ giving rise to stronger hydrogen bonds with the carboxylate moiety of zwitterionic glycine. This conjecture is supported by the computational results.Key words: high pressure mass spectrometry, glycine, gas-phase ion thermochemistry, ab initio calculations, cluster structure.
Synthesis, characterization, and single crystal X-ray structures of [CoIII(acacen)(thioacetamide)2]ClO4 and [CoIII((BA)2en)(thioacetamide)2]PF6  Solvatochromic properties of [CoIII(acacen)(thioacetamide)2]ClO4
Authors: Amirnasr Mehdi , Langer Vratislav , Rasouli Nahid , Salehi Mehdi , Meghdadi Soraia
Published: March 2006

The trans-[CoIII(acacen)(ta)2]ClO4 (1) and trans-[CoIII((BA)2en)(ta)2]PF6 (2) complexes, where H2acacen = bis(acetylacetone)ethylenediimine, H2(BA)2en = bis(benzoylacetone)ethylenediimine, and ta = thioacetamide, have been synthesized by a solid-state method, and characterized by elemental analyses, IR, UVvis, and 1H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography. Both compounds crystallize in the monoclinic space group P2/n. The ClO4 and PF6 ions are both disordered, ClO4 on a twofold axis in 1 and PF6 on an inversion center in 2. Also bridging N-CH2-CH2-N is disordered in both compounds. The octahedral coordination of Co(III) is slightly distorted in both cases. The thioacetamide ligands are S-bonded and occupy the axial position. The IR, UVvis, and 1H NMR spectra of the two complexes and their solvatochromic properties are also discussed. The longest wavelength absorption that appears at 517 nm for 1 and at 528 nm for 2 in chloroform is solvent dependent, and is assigned as a metal-mediated ligand-to-ligand charge transfer (LLCT).Key words: solid-state synthesis, thioactamide, Co(III) (Schiff base), crystal structure, solvatochromism, metal-mediated LLCT.
Dihydropyrimidinones containing boronic acids
Authors: Blacquiere Johanna M , Sicora Oana , Vogels Christopher M , Čuperlović-Culf Miroslava , Decken Andreas , Ouellette Rodney J , Westcott Stephen A
Published: March 2006

The addition of formylphenylboronic acid derivatives to urea and ethyl acetoacetate proceeds in the absence of an additional Lewis acid catalyst to give the corresponding dihydropyrimidinones (Biginelli products) in good yields. Novel boron-containing dihydropyrimidinones have been investigated for their ability to act as anticancer agents against the breast cancer cell line MCF7.Key words: anticancer, Biginelli compounds, boronic acids, breast cancer, dihydropyrimidinones.
SnCl4I2 mediated regioselective 6-endo- and 5-exo-cyclization of ortho-allylenols
Authors: Majumdar K C , Biswas A , Mukhopadhyay P P
Published: March 2006

3-Allyl-4-hydroxycoumarins and 4-allyl-3-hydroxycoumarins are obtained in 90%92% yields by the thermal [3,3] sigmatropic rearrangement of the corresponding ethers. 3-Allyl-4-hydroxy-6-methylpyrone is obtained from the direct alkylation of 4-hydroxy-6-methylpyrone with allyl halide. These substrates on treatment with SnCl4I2 at 25 °C give a mixture of both 5-exo- and 6-endo-cyclization products. However, regioselective formation of 5-exo products is observed when the reactions are conducted at lower temperatures (05 °C, kinetically controlled), while the reaction at a higher temperature (50 °C, thermodynamically controlled) affords regioselectively 6-endo cyclization products.Key words: stannic chloride, iodine, claisen rearrangement, 6-endocyclization, 5-exocyclization, kinetically controlled reaction, thermodynamically controlled reaction.
Activation of methane by gaseous platinum(II) ions PtX+ (X = H, Cl, Br, CHO)
Authors: Schröder Detlef , Schwarz Helmut
Published: March 2006

The gas-phase reactions of methane with the platinum(II) ions PtX+ with X = H, Cl, Br, and CHO are studied by mass spectrometry. The PtX+ ions are generated by electrospray ionization of methanolic solutions of hexachloroplatinic acid and hexabromoplatinic acid, respectively. Small to moderate intramolecular kinetic isotope effects determined for the CH(D) bond activation of CH2D2 suggest that the activation of methane by gaseous PtX+ cations is subject to thermochemical control by the product channels. In addition, the PtCl2+ cation is also able to activate methane, whereas PtCl3+ is unreactive under the conditions chosen. Key words: gas-phase reactions, mass spectrometry, methane activation, platinum bromide, platinum chloride.
The gas-phase acidities of the elemental hydrides are functions of electronegativity and bond length
Authors: Bartmess John E , Hinde Robert J
Published: March 2006

The gas-phase Brønsted acidities of the group 1, group 2, and main group elemental hydrides (XHn) are shown to be a combined function of the bond length, electronegativity, and position in the periodic table, via a separation of the acidity into coulombic and electronic reorganization enthalpy parts. The Coulombic acidity is defined as the enthalpy to separate unit positive and negative charges from the neutral acid's XH bond length to infinity; the reorganization enthalpy is the difference between that and the measured acidity, and represents the enthalpy required to reorganize the electrons of the neutral acid, creating an ion pair at the original bond distance. Predictions are made for the gas-phase Brønsted acidities of several elemental hydrides for which this quantity is not known.Key words: acidity, gas phase, coulomb, elements, hydride.
A convenient solid-phase synthesis methodology for preparing peptide-derived molecular imaging agents  Synthesis, characterization, and in vitro screening of Tc(I)  chemotactic peptide conjugates
Authors: Stephenson Karin A , Banerjee Sangeeta Ray , McFarlane Nicole , Boreham Douglas R , Maresca Kevin P , Babich John W , Zubieta Jon , Valliant John F
Published: March 2006

A versatile solid-phase synthesis strategy for preparing peptidechelate conjugates was developed. The methodology was optimized using a series of ligands, designed to bind Tc(I)/Re(I), and a chemotactic peptide fMFL, which was exploited as a model targeting vector. The peptide derivatives were prepared in parallel using a conventional automated peptide synthesizer in multi-milligram quantities, which provided sufficient material to perform complete characterization, radiolabelling, and in vitro screening studies. Because of the robust nature of the metalchelate complexes, the Re complex of a chelatepeptide conjugate was prepared on the resin using the same methodology employed to prepare the free ligand conjugates. As such, the reported methodology is amenable to the preparation of libraries of novel Tc radiopharmaceutical ligands and their corresponding Re reference standards in which several factors, including peptide sequence, site of derivatization, and both the type and length of the spacer, can be easily varied.Key words: radiopharmaceuticals, technetium, rhenium, peptides, solid-phase synthesis.
Structural analysis of acetylated hardwood lignins and their photoyellowing properties
Authors: Pu Yunqiao , Ragauskas Arthur J
Published: March 2006

Lignin was isolated from aspen bleached chemithermomechanical pulp by employing a mild acid hydrolysis procedure, and the extracted material was acetylated with acetic anhydride. Nuclear magnetic resonance analyses indicated that the relative ease of acetylating lignin hydroxyl groups was phenolic >> γ-side chain > α-side chain. Non-acetylated and acetylated lignins were impregnated onto cellulosic test sheets, and the photo-behavior of the lignins was examined under irradiation with two light sources, a fluorescent lamp and a black lamp. Optical reflective studies indicated acetylation efficiently inhibited the photodiscoloration of aspen bleached chemithermomechanical pulp lignin under visible and near-UV light irradiation. The photostability of the lignin was correlated to the extent of lignin acetylation. The observed photo-stabilization of acetylated lignin during light irradiation was attributed to the acetylation of phenoxy and aliphatic hydroxyl groups in lignin.Key words: green chemistry, hardwood lignin, acetylation, photo-stabilization, photoyellowing, NMR.
Ab initio study of the decomposition of formamidine
Authors: Almatarneh M H , Flinn C G , Poirier R A
Published: March 2006

The decomposition of formamidine yielding hydrogen cyanide and ammonia has been investigated by ab initio calculations. Optimized geometries for reactants, transition states, and products were determined at the HF/6-31G(d) and MP2/6-31G(d) levels of theory. Energies were also determined at the G1, G2, G2MP2, G3, G3B3, G3MP2, and G3MP2B3 levels of theory. The role of water in the decomposition reaction of formamidine was examined. Intrinsic reaction coordinate (IRC) analysis was carried out for all transition states. Activation energies, enthalpies and free energies of activation were also calculated for each reaction pathway. G3 level of theory predicts the gas-phase decomposition of formamidine to have a high activation energy of 259.1 kJ mol1. Adding one water molecule catalyses the reaction by forming a cyclic hydrogen-bonded transition state, reducing the barrier to 169.4 kJ mol1 at the G3 level. Addition of a second water, which acts as a "solvent" molecule, further reduces the barrier to 151.1 kJ mol1 at the G3 level. These values are still high and explain why rather extreme conditions are necessary to achieve this reaction experimentally. Thermodynamic properties (ΔE, ΔH, and ΔG) for each reaction pathway studied were also calculated. The G3 heats of reaction (ΔE) of the gas-phase decomposition of formamidine, its complex with one water molecule, and its complex with two water molecules are 0.9, 2.2, and 5.1 kJ mol 1, respectively. The G3 heat of reaction for the gas-phase decomposition to yield separated products is 22.3 kJ mol1. Free energies of reaction and of activation in aqueous solution were calculated with PCM using the KLAMT cavity model. At MP2 the formamidine reaction is found to be exergonic in aqueous solution and to favour formation of the separated products (NH3 + HCN). The solvent model predicts a significant lowering of the free energy of activation (1618 kJ mol1) for the unimolecular reaction and 2142 kJ mol1 for the water-mediated reaction in aqueous solution relative to the gas phase. Key words: decomposition reaction, formamidine, HartreeFock, post HartreeFock, Gaussian-n theories, IRC, solvation models, PCM, KLAMT.
Steric effects in the phototransposition reactions of dialkylbenzenes
Authors: Gonzalez C M , Pincock J A
Published: March 2006

The photochemistry, photophysical properties, and temperature dependence (25 to +65 °C) of fluorescence by quantum yields and excited singlet state lifetimes in acetonitrile have been examined for three sets of dialkylbenzene derivatives: Set 1  ortho-xylene (10), tetralin (11), and indan (12); Set 2  2,3-dimethylbenzonitrile (9-23), 5-cyanotetralin (T-23), and 4-cyanoindan (I-23); and Set 3  3,4-dimethylbenzonitrile (9-34), 6-cyanotetralin (T-34), and 5-cyanoindan (I-34). Phototransposition reactions occur for 10, 9-23, 9-34, and T-34. Fitting of the temperature-dependent fluorescence data to an Arrhenius expression gave A and Ea values for all substrates studied except I-23 and I-34. The fluorescence intensity of these two compounds was essentially independent of temperature. For the other compounds, the data revealed that the activation barrier separating the excited singlet state (S1) from the reactive intermediate, a prefulvene biradical, was the important one in determining the reaction efficiency. The dominant mode of decay of the reactive intermediate was internal return to the starting material. Moreover, the general observation was made that nitrile substitution ortho to one of the alkyl groups in these dialkylbenzene derivatives reduced the rate at which they were converted to the reactive intermediate and, therefore, also the efficiency of the phototransposition reactions.Key words: phototranspositions, substituted benzenes, temperature-dependent fluorescence, activation parameters.
Preparation, spectroscopic characterization, and deprotonation reactions of Si(NHR)4 (R = i-Pr, t-Bu, p-tolyl)  EPR identification of persistent radicals formed by oxidation of polyimidosilicates
Authors: Armstrong Andrea F , Chivers Tristram , Konu Jari
Published: March 2006

Treatment of Cl2Si(NH-t-Bu)2 (6a) with t-BuNH2 in boiling toluene yields trisamino(chloro)silane ClSi(NH-t-Bu)3 (7); formation of the tetraaminosilane Si(NH-t-Bu)4 is not observed. The reaction of SiCl4 with 4 equiv. of LiNHR produces the corresponding tetraaminosilanes Si(NHR)4 (2a, R = i-Pr; 2b, R = t-Bu; 2c, R = p-tol) in good yields. When the sterically demanding adamantyl derivative LiHNAd is employed, only disubstitution occurs to form Cl2Si(NHAd)2 (6b). Oxidation of the dimeric imidosilicates {Li3[Si(NR)3(NHR)]·THF}2 (3a, R = i-Pr; 3b, R = t-Bu) with 1 mol of iodine produces the persistent radicals {Li2[Si(NR)3(NHR)]·LiI·3THF}·, which, on the basis of EPR spectra, exist as SiN3Li3I cubes in solution. The spirocyclic tetraimidosilicate monoanion radical {[(THF)2Li(µ-Nnaph)2Si(µ-Nnaph)2Li(THF)2]}· (10) is formed upon oxidation of the tetralithiated species {Li4[Si(Nnaph)4]·4Et2O} (1) and {[Li(12-crown-4)]2[(Et2O)2Li(µ-Nnaph)2Si(µ-Nnaph)2Li(Et2O)2]} (8) with iodine. The spectroscopic characterization of hexa(amino)disiloxane (t-BuNH)3SiOSi(NH-t-Bu)3 (14) formed from the reaction of Cl3SiOSiCl3 with 6 equiv. of LiNH-t-Bu is discussed. Key words: imido ligands, silicate, radicals, EPR spectra, lithium.
THE CUTOFF TRANSACTION SIZE OF A QUADRATIC CONCAVE HOLDING AND PENALTY COST FUNCTIONS TO THE INFORMATION VALUE APPLYING TO THE NEWSBOY MODEL
Authors: LIN CHIN-TSAI , TSAI HUI-YIN
Published: March 2006

This investigation adopts the perspective of the retailer and incorporates information flow between a retailer and customers. Two new models are considered that differ in terms of information completeness. The first model involves the retailer having incomplete information regarding the state of customers demand, namely extending the model of Dekker et al. (IIE Transactions, 32, 2000, 461) by considering the quadratic concave holding and penalty cost functions based on the law of diminishing marginal cost to fit in with the some practical situations. Meanwhile, the second model involves the retailer having full information on the state of customers demand. Precise expressions are derived for the expected total profit of these two newsboy models with a cutoff transaction size and compound Poisson demand distribution. It is worthwhile to measure the value of information and identify the effect of factors for enterprise decision making regarding whether or not to pay for information that can help increase profits. Moreover, we adopt and modify the golden section search technique (Haftka et al., 1990) to determine an optimal order-up-to level S and a cutoff transaction size q systematically. Finally, numerical examples are given to illustrate the result derived.
IMPERFECT PRODUCTION SYSTEMS WITH IMPERFECT PREVENTIVE MAINTENANCE, INFLATION, AND TIME VALUE OF MONEY
Authors: DARWISH M. A.
Published: March 2006

A model that integrates the issues of production, quality, maintenance, inspection, inflation, and time value of money is proposed in this paper. It is assumed that the production system starts in the in-control state producing items of high or perfect quality. However, the process may deteriorate with time and shifts at a random point in time to an out-of-control state and begins to produce non-conforming items. The elapsed time for the process to shift to the out-of-control state is assumed to follow a general distribution. Imperfect preventive maintenance, restoration, and inspection errors are taken into account. Also, inflation, time value of money, and shortage are considered in the proposed model. Numerical examples are presented to illustrate important aspects of the integrated model.
SCATTERING MECHANISM OF HIGH ENERGY STRONG INTERACTION SOFT PROCESSES
Authors: PENG HONGAN , XING XIUWEN , LIU LIANSHOU
Published: March 2006

Starting from the viewpoint that the constituent quark has its own structure and incorporating the hypothesis of maximum nonperturbative strong interaction reaction (MNSIR), which should be obeyed in high energy strong soft processes, we modified the field theory for soft Pomeron (ℙ) of Landshoff and Nachtmann and proposed a new structure model for the soft Pomeron ℙ and Reggeon ℝ. In this model a pair of constituent quarks coming from colliding hadron in strong soft processes are first disaggregated into a valance quark with a nonperturbative gluon cloud G wrapped about, or, according to the case, into a nonperturbative gluon wrapped by spinor cloud. Corresponding to such mechanism, the relevant structure of soft Pomeron ℙ or Region ℝ is represented by the sum of a series of cut ladder diagrams. In the multi-Regge region, where the energy of the system is very large and the momentum transfer |t| is very small, and in the approximation where only the leading order of log s is preserved, we calculated the [Formula: see text] scattering amplitude and its total cross-section from the sum of such ladder diagrams. The Regge-behavior factor in the form of an exponential power law of s does arise. We also get compact formulas for the trajectories of soft ℙ and ℝ. As example of application, an alternative mechanism of J/Ψ nonquarkonic-hadron decay is proposed.
"SQUARE ROOT" OF THE PROCA EQUATION: SPIN-3/2 FIELD EQUATION
Authors: KRUGLOV S. I.
Published: March 2006

New equations describing particles with spin-3/2 are derived. The nonlocal equation with the unique mass can be considered as "square root" of the Proca equation in the same sense as the Dirac equation is related to the Klein–Gordon–Fock equation. The local equation describes spin-3/2 particles with three mass states. The equations considered involve fields with spin-3/2 and spin-1/2, i.e. multispin 1/2, 3/2. The projection operators extracting states with definite energy, spin, and spin projections are obtained. All independent solutions of the local equation are expressed through projection matrices. The first order relativistic wave equation in the 20-dimensional matrix form, the relativistically invariant bilinear form and the corresponding Lagrangian are given. Two parameters characterizing nonminimal electromagnetic interactions of fermions are introduced, and the quantum-mechanical Hamiltonian is found. It is proved that there is only causal propagation of waves in the approach considered.
THE X(3872) MESON AND "EXOTIC" SPECTROSCOPY AT CDF II — OR NOT? —
Authors: BAUER G.
Published: March 2006

A spate of remarkable new hadrons reported in 2003 may lead to unequivocal proof of states beyond conventional [Formula: see text] and qqq structure. Claimed baryonic states Θ+, Φ, and [Formula: see text] would consist of five quarks, and new [Formula: see text]-states and/or X(3872) might contain four quarks. I review efforts to search for and study this "new" spectroscopy in [Formula: see text]-collisions with the CDF II detector. Pentaquark searches are negative, and no evidence for exotic analogs of DsJ-states was found. CDF has confirmed the X(3872). My main focus is the production and decay properties of the X(3872), and its possible interpretations.
GHOST COSMOLOGY: EXACT SOLUTIONS, TRANSITIONS BETWEEN STANDARD COSMOLOGIES AND GHOST EVOLUTION
Authors: KRAUSE AXEL , NG SIEW-PHANG
Published: March 2006

The recently proposed infrared modification of gravity through the introduction of a ghost scalar field results in a number of interesting cosmological and phenomenological implications. In this paper, we derive the exact cosmological solutions for a number of scenarios where at late stages, the ghost behaves like dark matter, or dark energy. The full solutions provide information about the nonlinear regime beyond the asymptotic analysis presented in the literature. The generic feature is that these ghost cosmologies give rise to smooth transitions between radiation dominated phases (or more general power-law expansions) at early epochs and ghost dark matter resp. ghost dark energy dominated late epochs. The current age of our universe places us right at the nonlinear transition phase. By studying the evolution backwards in time, we find that the dominance of the ghost over ordinary baryonic matter and radiative contributions persists back to the earliest times such that the Friedmann–Robertson–Walker geometry is dictated to a good approximation by the ghost alone. We also show that a Jeans instability arises in the ghost dark energy scenario at late times, while it is absent in the ghost dark matter scenario.
INTERPOLATING STATISTICS AND q-DEFORMED OSCILLATOR ALGEBRAS
Authors: NARAYANA SWAMY P.
Published: March 2006

The idea that a system obeying interpolating statistics can be described by a deformed oscillator algebra, or quantum groups, has been an outstanding issue. We are able to demonstrate that a q-deformed oscillator algebra can be used to describe the statistics of particles which provide a continuous interpolation between Bose and Fermi statistics. We show that the generalized intermediate statistics splits into Boson-like and Fermion-like regimes, each described by a unique oscillator algebra. The thermostatistics of Boson-like particles is described by employing q-calculus based on the Jackson derivative while the Fermion-like particles are described by ordinary derivatives of thermodynamics. Thermodynamic functions for systems of both types are determined and examined.
COMBINED EFFECTS OF RASHBA SPIN-ORBIT INTERACTION STRENGTH AND ITS EXTENDED LENGTH IN QUANTUM WIRES
Authors: SU HUI , GU BEN-YUAN
Published: March 2006

The combined effects of Rashba spin-orbit interaction (SOI) strength and the length of SOI excited region, which can be controlled by the external gate voltage deposited on the heterostructure, and on the electron spin precession in quasi-one-dimensional quantum wires are investigated by evaluating the relative conductance change, i.e. the ratio of difference of the conductances of the spin-up and spin-down polarized electrons to the total conductance. It is found that for proper wire width, electron spin precession can be smoothly achieved by co-adjusting the SOI strength and the length of SOI excited region. However, for wide quantum wire and strong SOI, the electron spin precession is significantly reduced due to the appearance of inter-subband mixing.