bluuebunny/crossref_metadata_2025 huggingface dataset:
The Schizosaccharomyces pombe septation initiation network (SIN) is required for spore formation in meiosis
Authors: Krapp Andrea , Collin Philippe , Cokoja Adisa , Dischinger Sandra , Cano Elena , Simanis Viesturs
Published: June 2006

When nutrients are abundant, S. pombe cells grow as rods, dividing by fission after formation of a medially placed cell wall or division septum. Septum formation is triggered by a group of proteins, called the septation initiation network or SIN, that trigger contraction of the acto-myosin contractile ring at the end of mitosis. Ectopic activation of the SIN can uncouple septum formation from other cell-cycle events, whereas loss of SIN signalling gives rise to multinucleated cells due to the failure of cytokinesis. When starved, S. pombe cells of opposite mating types fuse to form a diploid zygote that undergoes meiosis and produces four spores. No septa or contractile rings are formed during meiosis. In this study, we have investigated the role of the SIN in meiosis. Our data show that, whereas the meiotic divisions appear normal, SIN mutants cannot form spores. Forespore membrane formation is initiated, but the nuclei are not encapsulated properly. The SIN proteins localise to the spindle pole body in meiosis. The protein kinases Sid1p and Cdc7p do not associate with the spindle pole body until meiosis II, when forespore membrane deposition begins. These data indicate a role for the SIN in regulating spore formation during meiosis.
Pharmacological characterization of the ergot alkaloid receptor in the salivary gland of the ixodid tickAmblyomma hebraeum
Authors: Kaufman W. Reuben , Minion Jessi L.
Published: June 2006

Female ticks of the family Ixodidae osmoregulate by secreting the excess fluid of the blood meal back into the host's circulation via the salivary glands. At least three receptors control salivary fluid secretion in the tick Amblyomma hebraeum: (1) dopamine (DA) stimulates fluid secretion via a DA receptor, (2) ergot alkaloids (ErAs) stimulate fluid secretion via an ErA-sensitive receptor (the natural ligand of which has not been identified), and (3) a GABA receptor potentiates the action of DA and ErAs. Here we present some pharmacological properties of the ErA-sensitive receptor. Of the 11 ErAs we tested, (i) four were complete agonists (approximate concentration eliciting 50% maximum response is given in parentheses): dihydroergotamine (0.02 μmol l–1),ergonovine (ErN; 0.06 μmol l–1), methylergonovine (0.1μmol l–1) and α-ergocriptine (0.9 μmol l–1); (ii) three were `incomplete agonists' (approximate concentration eliciting 20% maximum response is given in parentheses):ergocorninine (3.5 μmol l–1), ergocristinine (7.5 μmol l–1) and ergocristine (10 μmol l–1); (C)three were partial agonists (approximate concentration eliciting the respective maximum response in parentheses): ergocornine (50% maximum by 1μmol l–1), methysergide (28% maximum by 10 μmol l–1) and bromocriptine (22% maximum by 10 μmol l–1); and (D) one had no activity up to 1 mmol l–1: ergothioneine. Bromocriptine and methysergide did not antagonize the action of DA, but were effective competitive antagonists of ErN, with Kis of ∼0.3 μmol l–1 and 11 μmol l–1, respectively. Ergothioneine was not an antagonist at either the DA- or ErA-sensitive receptor. The putative protein kinase C activators, 1-oleoyl-2-acetyl-sn-glycerol (OAG) and 1,2-dioctanoyl-sn-glycerol (DiC8), neither stimulated salivary fluid secretion nor potentiated the action of DA or ErN. The putative protein kinase C inhibitors, bisindolymaleimide (BIM) and calphostin C did not inhibit the action of DA or ErN, although low concentrations of calphostin C(10 nmol l–1) appeared to potentiate the action of DA but not ErN. The ion transport inhibitors, furosemide and amiloride (both up to 1 mmol l–1), had no significant effect on DA-stimulated or ErN-stimulated fluid secretion.
Water vapour absorption in the penicillate millipedePolyxenus lagurus(Diplopoda: Penicillata: Polyxenida): microcalorimetric analysis of uptake kinetics
Authors: Wright Jonathan C. , Westh Peter
Published: June 2006

The aberrant millipedes of the order Polyxenida are minute animals that inhabit xeric microclimates of bark and rock faces. The lichens and algae that provide their main food substrates tolerate extensive dehydration, effectively eliminating a liquid water source during periods of drought. In this study, we used microcalorimetry to test whether Polyxenus lagurus (L.) exploits active water vapour absorption (WVA) for water replenishment. Individual animals were pre-desiccated to 10–20% mass-loss and heat fluxes then monitored using a TAM 2277 microcalorimeter. The calorimetric cell was exposed to an air stream increasing progressively in humidity from 84% to 96%. WVA was distinguishable as large exothermic fluxes seen in ≥86% RH. Owing to very small and opposing heat fluxes from metabolism and passive water loss, the measured flux provided a good measure of water uptake. WVA showed an uptake threshold of 85% RH and linear sorption kinetics until >94% RH, when uptake became asymptotic. Uptake was rapid, and would allow recovery from 20%dehydration (by mass) in little over 5 h. The uptake flux scales ∝mass0.61, suggesting an area-limited mechanism. Polyxenuspossesses a cryptonephric system, analogous to that of tenebrionid beetle larvae. Measurements of water absorption and desorption from faecal pellets voided in different humidities gave an estimated rectal humidity of 85.5%. The close congruence between this value and the WVA threshold provides evidence for a cryptonephric uptake mechanism derived independently from that of tenebrionids. Polyxenus represents the first documented example of WVA in the myriapod classes.
Polyorganosilicon Compounds in Strained Carbocyclic Systems
Authors: Ando Wataru
Published: June 2006

Organosilicon chemistry has been highlighted by the successful construction and thorough characterization of strain carbocyclic systems: 1) silabenzene, silafulvene, and polycyclic polysilane via a silylcarbene rearrangement to silene, 2) a ring-expansion reaction of disilacyclobutene with exo-methylene, and 3) cyclic polysilanes containing unsaturated carbon systems, such as acetylene, allene, and fullerene. Some of these numerous compounds, which are now available, are fully substituted with bulky ligands. These compounds permit examinations of: 1) the variation in the physical and chemical properties of a system with polysilane, and 2) how the systems are related thermally and photochemically with carbon analogues. Some cyclic polysilanes may constitute a stepping stone on the way to super-molecules.
Selective Adsorption of Lipopolysaccharide from Protein Solutions by Porous Supports Bearing Cationic Lipid Membranes
Authors: Wakita Masa-aki , Adachi Tsuneyasu , Ida Jun-ichi , Hashimoto Masanori
Published: June 2006

Cationic lipid membranes of N-octadecylchitosan consisting of 2-deoxy-2-octadecylamino-d-glucopyranose, 2-amino-2-deoxy-d-glucopyranose, and 2-acetamido-2-deoxy-d-glucopyranose were covalently immobilized to carboxylated porous supports and used for the adsorption of pyrogenic lipopolysaccharide (LPS). When bovine serum albumin (BSA) solution, including 5 mg mL−1 of BSA and 100—148 ng mL−1 of LPS, was passed through a column packed with the porous supports bearing the cationic lipid membranes, LPS was selectively adsorbed and removed to as low as 0.1 ng mL−1 with quantitative recovery of BSA. LPS seemed to be dissociated from molecular complexes with BSA, and adsorbed selectively to the cationic lipid membranes by both an ionic interaction and a hydrophobic one.
Syntheses of Highly Ordered Mesoporous Materials, FSM-16, Derived from Kanemite
Authors: Inagaki Shinji , Koiwai Akihiko , Suzuki Noritomo , Fukushima Yoshiaki , Kuroda Kazuyuki
Published: June 2006

The synthetic conditions of highly ordered and thermally stable mesoporous molecular sieves from a layered silicate kanemite are established. We divided the formation process of the mesoporous materials from kanemite into two elemental processes: i) exchange of Na+ in the interlayer of kanemite for alkyltrimethylammonium cations and ii) condensation of silicates and formation of a three dimensional silicate framework. Higher pH (over 11.5) at the cation-exchange process and the subsequent pH adjustment at 8.5 at the condensation process were best suited for the formation of mesoporous products with high regularity and thermal stability. Removal of partially dissolved kanemite during the cation-exchange process avoided the formation of amorphous materials as a by-product. Structures of some intermediate silicate/surfactant complexes supported the proposed folded sheets mechanism for the formation of the mesoporous molecular sieves. Syntheses by using alkyltrimethylammonium with different alkyl-chain lengths are also reported.
Inter-Peptide Hydrogen Bonding in Monolayers of Oligoglycine Amphiphiles
Authors: Cha Xiao , Ariga Katsuhiko , Kunitake Toyoki
Published: June 2006

N-Octadecanoyl oligoglycine (monomer to pentamer) ethyl esters were synthesized. The structures of their monolayers and LB films transferred from pure water were investigated by π–A isotherms and FT-IR reflection absorption spectroscopy (FT-IR, RAS). All the glycine residues were involved in intermolecular hydrogen bonding as indicated by shifts of the NH stretching band and other IR features. The strength of the hydrogen bonds was increased with increasing numbers of the glycine residues in a molecule. The FT-IR characteristics of these monolayers are close to those of polyglycine II, despite the fact that these oligopeptides are not long enough for conformational fixation in bulk water.
Reversible Electrochromism of Copper Phthalocyanine Thin Film
Authors: Toshima Naoki , Tominaga Tsuyoshi , Kawamura Shin-ichi
Published: June 2006

The electrochromism of copper phthalocyanine thin films was examined in detail under various conditions. The application of a positive voltage to copper phthalocyanine thin film exhibited two oxidation peaks in the range from 0 to 1.4 V. Although the color of the film changed from sky blue to pale gray upon scanning the voltage in this region, irreversible electrochromism was observed, leading to a deterioration of the film. The two oxidation peaks were concluded to represent two types of appearances of one reaction with different overpotentials caused by the structure of the crystal grains of the film. Control of the scan range to admit only the first oxidation peak provided a reversible electrochromism between sky blue and bluish purple. Electrolyte anions are also of great importance to accomplish reversible electrochromism. Thus, the anions should be stable for the application of a positive voltage, and their Stokes radii should be neither too large nor too small in order to achieve reversible electrochromism. Rather small anions provide almost Nernstian cyclic voltammograms and the quick color change.
Study of the Electronic Structure of GaAs(100) Single Crystal Electrode/Electrolyte Interfaces by Electrochemical Tunneling Spectroscopy
Authors: Uosaki Kohei , Ye Shen , Sekine Namiki
Published: June 2006

An electrochemical tunneling spectroscopy (ETS) system is constructed to study the electronic structure of semiconductor/electrolyte interfaces. By using this system, the tunneling current of GaAs (100) single crystal electrodes in solution was measured as a function of electrode potential at a constant sample-tip distance. Tunneling current flowed in the forward bias region; the current depended on the bias, i.e., the potential with respect to the flat band potential. It decreased by decreasing the bias and became zero near the flat band potential. This behavior can be explained by considering the potential dependence of the surface concentration of the majority carriers. The space charge layer within the semiconductor formed in the reverse bias region worked as an extra barrier for the tunneling process; therefore, no tunneling current was observed in this potential region. Current in the direction opposite to that in the forward bias region flowed as the reverse bias became very large, although this current was very small. In this potential region, the thickness of the space charge layer near the Fermi level of the tip became thinner and electrons were able to tunnel through the barrier. Effects of the doping density, the tip potential, the pre-set tunneling current and the initial sample potential as well as the surface treatment on the tunneling current–electrode potential relation were investigated in detail at n-GaAs(100) single crystal electrodes. The tunneling behaviors in the forward and reverse bias regions were discussed semi-quantitatively based on the calculation of surface electron concentration and the transmission coefficient through the space charge barrier, respectively.
Reactions of Si–Si σ-Bonds with Bis(t-alkyl isocyanide)palladium(0) Complexes. Synthesis and Reactions of Cyclic Bis(organosilyl)palladium Complexes
Authors: Suginome Michinori , Oike Hideaki , Park Sang-Soo , Ito Yoshihiko
Published: June 2006

Four- to seven-membered cyclic bis(organosilyl)palladium(II) complexes were synthesized by oxidative addition of cyclic disilanes onto bis(t-butyl isocyanide)palladium(0) as well as by intramolecular metathesis of the two Si–Si bonds of bis(disilane)s with the palladium(0) complex. The 4-membered bis(organosilyl)bis(t-butyl isocyanide)palladium complex prepared from 2,2-bis(1,1,2,2-tetramethyl-2-phenyldisilanyl)-1,3-dithiane was characterized by a single-crystal X-ray method, which showed an unusually short cross-ring Si–Si distance in the 4-membered ring. The reactivities of the cyclic bis(organosilyl)bis(t-butyl isocyanide)palladium complexes toward phosphines, cyclic disilanes, and alkynes were also examined. Cyclic organosilicon compounds were synthesized by bis-silylation of alkynes with cyclic bis(organosilyl)palladium intermediates generated by the intramolecular metathesis. The bis-silylation was also applicable for electron-deficient alkenes: α,β-unsaturated ketones gave 7-membered 1,4-bis-silylation adducts, whereas the corresponding ester and nitrile gave 5-membered 1,2-adducts in high yields.
Thermal Decomposition and Mass Spectra of the N-Phenyl-, N,N′-Diphenyl-, and N,N′,N″-Triphenylphosphoric Triamides
Authors: Fukushima Kazuhiko , Kanayama Atsushi , Matsumoto Yoshihiro , Ono Shin , Yoshimura Toshiaki , Morita Hiroyuki , Tsukurimichi Eiichi , Shimasaki Choichiro
Published: June 2006

The thermal decomposition and mass spectra of the N-phenyl- (1), N,N′-diphenyl- (2), and N,N′,N′-triphenylphosphoric triamides (3) were investigated. DTA-TG/DTG, TG-TRAP-GC/MS measurements, IR spectroscopic analyses, mass spectrometric analyses, HPLC analyses, and a kinetic study were carried out to investigate the thermal decomposition. From the analytical results, it was suggested that 1 decomposed while liberating ammonia and aniline, and condensed in several stages; its thermal products at about 160 °C contained 2. Compound 2 decomposed and condensed to form some condensed products at about 200 °C; its thermal products also contained 3. Compound 3 decomposed while liberating aniline to form a cyclic dimer, while the existence of other thermal products was also observed; the cyclic dimer further pyrolyzed in several stages, and 1 and 2 formed a similar condensed product in the 400 to 500 °C temperature range, though that for 3 was different. In addition, the apparent activation energy of the thermal decomposition was estimated and the thermal decomposition process was investigated based on this variation. In the mass spectra using electron impact, 1, 2, and 3 were cleaved along with an elimination of ammonia and/or aniline to form a three-coordinate phosphenimidic amide.
Rearrangement of Bicyclo[2.2.2]octa-2,5-diene and Bicyclo[3.2.2]nona-6,8-diene under the Conditions of Bromination
Authors: Satake Kyosuke , Hikasa Kazuyuki , Itoh Hajime , Okamoto Hideki , Kimura Masaru , Morosawa Shiro
Published: June 2006

A reaction of electrophilic bromination of norbornadiene homologs such as bicyclo[2.2.2]octa-2,5-diene (4) and bicyclo[3.2.2]nona-6,8-diene (7) with bromine gave hitherto unknown skeleton rearranged dibromides. The rearrangement may proceed via a bromonium cation of starting diene to give bicyclo[3.2.1]octene or bicyclo[3.3.1]nonene skeleton in respective cases. The observed rearrangement reactions are also confirmed in 6,7-bis(methoxycarbonyl) derivatives of bicyclodiene 7 under similar conditions.
Diethyl Ether–Boron Trifluoride (1/1) Induced Transannular Cyclization Reaction of Humulene 2,3-Epoxide
Authors: Hayano Kiyoharu , Shirahama Haruhisa
Published: June 2006

The treatment of (6E, 9E)-2,3-epoxy-3,7,11,11-tetramethylcycloundeca-6,9-diene with Et2O·BF3 produced four novel transannular cyclized compounds of (4E)-(1S*, 8S*, 9S*)-8-acetoxy-6,6,9-trimethyl-2-methylenebicyclo[7.2.0]undec-4-ene (13), (2Z, 4E)-(1S*, 8S*, 9S*)-8-acetoxy-2,6,6,9-tetramethylbicyclo[7.2.0]undeca-2,4-diene (14), (6E)-(1R*, 2R*, 3S*, 10R*)-3-acetoxy-2,5,5-trimethyl-9-methylenebicyclo[8.1.0]undec-6-ene (15), and (4E)-(1S*, 2S*, 8S*, 9S*)-2,8-diacetoxy-2,6,6,9-tetramethylbicyclo[7.2.0]undec-4-ene (16) together with three new acetates: (2E, 5E, 8E)-1-acetoxy-2,6,10,10-tetramethylcycloundeca-2,5,8-triene, (1E, 6E)-3,9-diacetoxy-2,5,5,9-tetramethylcycloundeca-1,6-diene, and (4E, 7E)-1-acetoxy-3,3,7-trimethyl-11-methylenecycloundeca-4,7-diene. The configurations of the bicyclo[7.2.0]undecane skeletons (13, 14, and 16) and 15 maintained the shape of TC and CT conformers of the original epoxide, respectively.
Effects of Solvent Fluctuations on the Rate of Thermal Z/E Isomerization of Azobenzenes and N-Benzylideneanilines
Authors: Asano Tsutomu , Cosstick Kevin , Furuta Hiroyuki , Matsuo Kohei , Sumi Hitoshi
Published: June 2006

Effects of pressure on thermal Z/E isomerization of substituted N-benzylideneanilines and azobenzenes were studied in 2-methyl-2,4-pentanediol. Pressure dependence of the Z/E isomerization of a substituted azonaphthalene was also studied in glycerol triacetate. From the results in this and earlier papers, the following conclusions were reached. 1) It is possible to cast slow thermal reactions into the state of fluctuation control in highly viscous liquid phase realized by a combination of a viscous liquid and high pressure. 2) The viscosity dependence of the rate constant can be rationalized by the two-dimensional reaction-coordinate model developed by Sumi but not by the Grote–Hynes’ theory of frequency-dependent friction. Namely, the energy-barrier crossing takes place after the solvent molecules are rearranged to accommodate the transition state. 3) Whether the solvent rearrangement involves chemical transformations with appreciable energy increases depends on the nature of the reaction and the solvent.
Isomer Compositions of Trimethyl- or Trichlorobenzenes in α-Cyclodextrin Precipitates Formed in an Aqueous Medium
Authors: Sanemasa Isao , Wu Yue , Sato Takayuki , Samejima Kaoru , Koide Yuuki , Takaki Noriyuki , Toda Kei , Deguchi Toshio
Published: June 2006

Upon introducing the vapor of binary mixtures of trimethylbenzene (TMB) or trichlorobenzene (TCB) isomers into an α-cyclodextrin (α-CyD) aqueous solution, and circulating it in a closed system, CyD was precipitated with the isomers. In (1,3,5–1,2,3 or 1,2,4,)-TMB systems of various mixing ratios, the mole fraction of 1,3,5-TMB in the total TMBs precipitated was considerably lower than that of 1,2,3- or 1,2,4-TMB: selective precipitation of 1,2,3- or 1,2,4-TMB occurred in the presence of 1,3,5-TMB. The concentration of α-CyD in the supernatant aqueous solution was determined as a function of the isomer mixing ratio. The selectivity was rather poor in the cases of TCB systems. Ternary mixtures of TMB isomers were also studied to a less extent. The solubility product constants at 25 °C were proposed for TMB and TCB precipitates with α-CyD.
Syntheses, Structures, and Molecular-Orbital Calculations of Chromium Chevrel-Type Cluster Complexes [Cr6E8(PR3)6] (E = S, PR3 = PEt3, PMe3; E = Se, PR3 = PEt3, PMe3, PMe2Ph)
Authors: Tsuge Kiyoshi , Imoto Hideo , Saito Taro
Published: June 2006

Hexanuclear chromium cluster complexes [Cr6E8(PR3)6] (E = S, PR3 = PEt3, PMe3; E = Se, PR3 = PEt3, PMe3, PMe2Ph) were prepared by the reaction of anhydrous chromium dichloride, a trialkylphosphine, and either NaSH or Na2Se in methanol. The complexes comprised the Cr6 octahedra with eight face-bridging chalcogen atoms and six terminal phosphine ligands. Though the overall ligand arrangements were the same, the symmetry of the central Cr6 octahedra was Oh in PEt3 complexes, but distorted to D3d and D2h in PMe3 and PMe2Ph complexes, respectively. Because of a weakness of the metal–metal interaction, the steric and electronic effect complementarily caused a variation in the chromium octahedra. The electronic effect was analyzed by molecular-orbital calculations using the DV-Xα method.
Laser Flash Photolysis in High-Speed Photopolymer Coating Layers: Effects of Incorporating Dimethyl Phthalate as a Plasticizer into Coating Formulation
Authors: Urano Toshiyuki , Nagasaka Hideki , Shimizu Makoto , Takahara Shigeru , Yamaoka Tsuguo
Published: June 2006

The sensitization mechanisms of ketocoumarin dyes with a radical-generating reagent, 10,10′-carbonylbis[1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one] (KCD-J), 7,7′-bis(diethylamino)-3,3′-carbonyldicoumarin (KCD-DA) with 3,3′,4,4′-tetrakis(t-butyldioxycarbonyl)benzophenone (I) in poly(methyl methacrylate) film containing dimethyl phthalate (DMP) as a plasticizer have been investigated by laser flash photolysis using a total reflection cell. The fluorescence of the dyes was efficiently quenched by I in PMMA containing 50 wt% of DMP (film A) against total solid with static quenching distances of 12.5 and 12.7 Å for KCD-J and KCD-DA. The static quenching distance was around 1.5 times longer than that in PMMA. The decay time of the triplet in a film A was slightly quenched by I with a kq of less than 1.5 × 106 mol−1 dm3 s−1 for KCD-J and KCD-DA.

These results show that a static singlet sensitization from the fluorescent excited dyes to I is the predominant process in film A, suggesting the same predominant static singlet sensitization process in a PMMA film containing acrylate monomer, and the static quenching distance is increased by incorporation of DMP into PMMA film.
Sequence Effects on Helix-Sheet Conformational Transitions of Designed Amphiphilic Peptides
Authors: Fukushima Yasumasa
Published: June 2006

Four 18-residue amphiphilic peptides were designed and synthesized, and their helix-sheet conformational transitions were investigated by circular dichroism (CD) in aqueous solution at different pH, peptide concentration and ionic strength as well as in a water/HFIP mixture. The α-helical conformations existed as monomeric states, while the β-sheet structures were formed by the aggregation of approximately 6 monomeric peptides for Peptide I, II, and III. The conformational transitions were provided by the self-association and dissociation of each peptide. The aggregated β-sheet structures would be stabilized by intermolecular hydrophobic interactions and complementary ionic bonds in addition to the conventional hydrogen bonds. In contrast, the formation of α-helical conformations would be caused by intramolecular electrostatic interactions between charged residues and the intrinsic high α-helix propensities of constituent amino acids in addition to hydrogen bonds. These peptides could be useful models for studying the factors governing the stability of secondary and tertiary structures as well as conformational transitions for comprehending the principles of how proteins fold into native states.
Synthesis, Structure, and Some Reactions of (2,4,6-Tri-t-butyl)thiobenzaldehyde, the First Stable Aromatic Thioaldehyde
Authors: Ishii Akihiko , Ishida Takashi , Kumon Naoko , Fukuda Nobuo , Oyama Hiroyuki , Inamoto Naoki , Iwasaki Fujiko , Okazaki Renji
Published: June 2006

The title compound 1 was synthesized by the reaction of 2,4,6-tri-t-butylphenyllithium with O-ethyl thioformate or that of 2,4,6-tri-t-butylbenzaldehyde hydrazone with disulfur dichloride in the presence of triethylamine. The thioaldehyde 1 is a purple crystalline compound which is thermally quite stable; only around 200 °C it underwent intramolecular cyclization to give 6,8-di-t-butyl-3,4-dihydro-4,4-dimethyl-1H-2-benzothiopyran 9. The X-ray crystallographic analysis of 1 revealed that the thioformyl group is almost perpendicular to the aromatic ring. The reaction of 1 with 1-cyano-1-methylethyl radicals afforded 9, while that with t-butyl radicals gave 1,3,5-tri-t-butyl-2-t-butylthiomethylbenzene and t-butyl 2,2-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-dien-2-yl)propyl sulfide in addition to 9. Some Grignard reagents and organolithiums reacted with 1 gave carbophilic, thiophilic, double addition products and some others depending on the kind of the organometallic reagents. Hydrazine and butylamine reacted with 1 very readily to give the corresponding hydrazone and imine, respectively.
Synthesis and Properties of High-Molecular-Weight Polypeptides Containing Tryptophan II. Copolypeptides of Tryptophan with Various Amino Acids
Authors: Uchida Chieko , Iizuka Yasuko , Ohta Eido , Wakamatsu Kaori , Oya Masanao
Published: June 2006

High-purity N-carboxyl l-tryptophan anhydride (l-4-indoylmethyl-2,5-oxazolidinedione) was synthesized in good yield. Copolypeptides with a random sequence of l-trypophan (Trp) with glycine (Gly), l-alanine (Ala), l-α-amino-n-butyric acid (Abu), l-n-valine (Nval), l-n-leucine (Nleu), l-leucine (Leu), l-γ-methylglutamate (Glu(OMe)), and l-methionine (Met) were synthesized by the copolymerization of the corresponding N-carboxy-α-amino acid anhydrides (NCA) in solution. The rate of polymerization of Trp NCA was less than that of the other amino acid NCAs. The helix contents of the formed copolypeptides, estimated by the circular dichroism (CD) spectra, were remarkably decreased at a content of about 8% of Trp involved in poly(Trp-co-Nval) (poly(Trp,Nval)), poly(Trp-co-Leu) (poly(Trp,Leu)), poly(Trp-co-Nleu) (poly(Trp,Nleu)), and poly(Trp-co-Glu(OMe)) (poly(Trp,Glu(OMe))), but was not decreased at that percentage in poly(Trp-co-Met) (poly(Trp,Met)).
Dye–Surfactant Interaction: Role of an Alkyl Chain in the Localization of Styrylpyridinium Dyes in a Hydrophobic Force Field of a Cationic Surfactant (CTAB)
Authors: Mishra Amaresh , Patel Sanjukta , Behera Rajani K , Mishra Bijaya K , Behera Gopa B
Published: June 2006

The interaction of a number of cationic dyes (I) with a varying number of methylene groups (Cn) in the alkyl chain attached to pyridyl nitrogen with a cationic surfactant (CTAB) assembly is reported. The binding constant of the dyes (C5 to C18) with the micelle have been calculated, and are found to increase with increasing carbon chain. A plot of the binding constant vs. the chain length shows a curve with a maximum for C16, which is attributed to a compatibility factor. From studies of the electronic and emission spectra it is proposed that a micelle has a hydrophobic force field and that the dyes are localized in various pockets of the field.
Molecular Structures of Zinc Complexes with Bisbenzimidazole Ligands in Crystals and the Kinetics of Ligand-Exchange Reactions in Their Solutions
Authors: Ogawa Kazuya , Nakata Kou , Ichikawa Kazuhiko
Published: June 2006

Zinc complexes with bisbenzimidazole, [ZnL(PhCOO)2] 1, [ZnLCl2] 2, and [ZnL2]2+  3, have been synthesized, where L = 2,2′-thiodimethylenebis(benzimidazole). Their molecular structures were determined based on X-ray crystal structure and extended X-ray absorption fine structure (EXAFS) analyses. The molecular structure of 1·1.5DMF shows a distorted tetrahedral geometry around Zn(II) coordinated by each nitrogen atom of two benzimidazolyl groups and each oxygen atom of two benzoate ions. In solutions of 2 or 3·(ClO4)2 the same chemical species, [ZnLCl2] or [ZnL2]2+, exist as in the coordination structure around zinc in each crystal. The combination of 13C NMR data with the most probable molecular structures of zinc complexes in 1, 2, and 3, determined by X-ray crystal structure and EXAFS analyses, allowed us to assign the two different chemical species, [ZnL(PhCOO)2] and [ZnL2]2+, as the major and minor components, respectively, in a solution of 1. A kinetic study of the ligand-exchange reaction between PhCOO− and L was provided us with the lifetimes of the chemical species of [ZnL(PhCOO)2] and [ZnL2]2+: 66 ms and 10 ms at −10 °C, respectively. The major species produced by a zinc-assisted supramolecular process in solution is the same type of chemical species [ZnL(PhCOO)2] as in the coordination structure around zinc in the crystal of 1·1.5DMF. The ESI mass spectra of a solution of 1, 2, and 3·(ClO4)2 supported the chemical species of [ZnL(PhCOO)2], [ZnL2]2+, and [ZnLCl2] in solution.
Photothermal Expansion of Droplets in Emulsions Detected by the Transient Grating Method
Authors: Tanzawa Kazunari , Hirota Noboru , Terazima Masahide
Published: June 2006

A nonlinear optical effect due to the thermal energy after the photoexcitation of a light-absorbing chromophore or a metal ion contained in micro droplets (oil in water (O/W) and water in oil (W/O)) was investigated by the time-resolved transient grating method. The temporal profiles of the diffusive components of the thermal grating signals are very different from that observed in a homogeneous solution, and also depend on the emulsion systems. The profiles were consistently analyzed in terms of the droplet heating, thermal expansion, and subsequent cooling process. The size of the droplets determined from this analysis agrees with that from the dynamic light scattering method.
Reactions of N(22D) with Alkane Hydrocarbons to Produce NH(X 3Σ−)
Authors: Umemoto Hironobu , Kimura Yuki , Asai Takashi
Published: June 2006

Ground state NH radicals could be detected as products of the reactions of N(22D) with simple alkane hydrocarbons. N(2D) was produced by two-photon dissociation of NO, while NH (X  3Σ−) was detected by laser-induced fluorescence. The nascent vibrational population ratio, NH(v″ = 1)/NH(v″ = 0), was determined to be 0.6, 0.5, 0.5, and 0.5 for CH4, C2H6, C3H8, and C(CH3)4, respectively. These ratios are smaller than that for H2, 0.8, but much larger than the prior ones. The nascent rotational state distributions of NH(X  3Σ−, v″ = 0) were determined for CH4, C2H6, and C3H8. The distributions were much hotter than the prior ones and showed little dependence on the complexity of the hydrocarbons. This suggests that the intermediate complexes which lead to the production of NH are short-lived and decompose before intramolecular vibrational redistribution (ivr). The yields for the production of NH(v″ = 0) for heavy alkanes were smaller than that for CH4. There must be exit channels other than NH production, such as C–C bond cleavage processes.
Structures and Magnetic Properties of Dinuclear Vanadium(III) Complexes with Alkoxo Bridge
Authors: Kanamori Kan , Yamamoto Kaori , Okayasu Takako , Matsui Naoto , Okamoto Ken-ichi , Mori Wasuke
Published: June 2006

Several dinuclear vanadium(III) complexes were prepared using a heptadentate dinucleating ligand containing a bridging alkoxo group. The structures of [V2(dpot)(m-hbza)(H2O)2]·H2O (1b), [V2(bza)(OH)(tphpn)(H2O)2]Cl3·8H2O (2), and [V2(hpnbpda)2]·12H2O (3a) were determined by X-ray crystallography (dpot: 2-oxo-1,3-diaminopropane-N,N,N′,N′-tetraacetate, m-hbza: m-hydroxybenzoate, bza: benzoate, tphpn: N,N,N′,N′-tetrakis(2-pyridylmethyl)-2-oxo-1,3-propanediamine, hpnbpda: N,N′-bis(2-pyridylmethyl)-2-oxo-1,3-propanediamine-N,N′-diacetate). Each vanadium(III) center of 1b adopts a distorted octahedral structure, and the two vanadium centers are bridged by an alkoxo group of dpot and a carboxylato group of m-hbza bridge. Each vanadium center of 2 and 3a, however, takes a heptacoordinate structure. The coordination polyhedron of 2 can be regarded as a capped octahedron, while that of 3a as a pentagonal bipyramid. The two vanadium(III) centers are ferromagnetically coupled in 1b (J = 23.7 cm−1) and 2 (J = 14.6 cm−1), whereas in 3a they are antiferromagnetically coupled (J = −35.2 cm−1). The electrochemistry of the dpot and hpnbpda complexes has also been investigated.
Two-Sided Competition of Proprietary vs. Open Source Technology Platforms and the Implications for the Software Industry
Authors: Economides Nicholas , Katsamakas Evangelos
Published: June 2006

Technology platforms, such as Microsoft Windows, are the hubs of technology industries. We develop a framework to characterize the optimal two-sided pricing strategy of a platform firm; that is, the pricing strategy toward the direct users of the platform as well as toward firms offering applications that are complementary to the platform. We compare industry structures based on a proprietary platform (such as Windows) with those based on an open source platform (such as Linux), and analyze the structure of competition and industry implications in terms of pricing, sales, profitability, and social welfare. We find that, when the platform is proprietary, the equilibrium prices for the platform, the applications, and the platform access fee for applications may be below marginal cost, and we characterize demand conditions that lead to this. The proprietary applications sector of an industry based on an open source platform may be more profitable than the total profits of a proprietary platform industry. When users have a strong preference for application variety, the total profits of the proprietary industry are larger than the total profits of an industry based on an open source platform. The variety of applications is larger when the platform is open source. When a system based on an open source platform with an independent proprietary application competes with a proprietary system, the proprietary system is likely to dominate the open source platform industry both in terms of market share and profitability. This may explain the dominance of Microsoft in the market for PC operating systems.
Location, Location, Location: How Network Embeddedness Affects Project Success in Open Source Systems
Authors: Grewal Rajdeep , Lilien Gary L. , Mallapragada Girish
Published: June 2006

The community-based model for software development in open source environments is becoming a viable alternative to traditional firm-based models. To better understand the workings of open source environments, we examine the effects of network embeddedness—or the nature of the relationship among projects and developers—on the success of open source projects. We find that considerable heterogeneity exists in the network embeddedness of open source projects and project managers. We use a visual representation of the affiliation network of projects and developers as well as a formal statistical analysis to demonstrate this heterogeneity and to investigate how these structures differ across projects and project managers. Our main results surround the effect of this differential network embeddedness on project success. We find that network embeddedness has strong and significant effects on both technical and commercial success, but that those effects are quite complex. We use latent class regression analysis to show that multiple regimes exist and that some of the effects of network embeddedness are positive under some regimes and negative under others. We use project age and number of page views to provide insights into the direction of the effect of network embeddedness on project success. Our findings show that different aspects of network embeddedness have powerful but subtle effects on project success and suggest that this is a rich environment for further study.
Strategic Interaction and Knowledge Sharing in the KDE Developer Mailing List
Authors: Kuk George
Published: June 2006

In stark contrast with the fully participative “bazaar” imagery of open source software (OSS) development, some recent empirical research has pointed out that much of the OSS development is carried out by a small percentage of developers. This raises serious concerns that concentration of development effort on a few will limit knowledge sharing and underutilize the available resources. Using the notion of strategic interaction, this paper argues that individual developers often interact strategically with other highly resourceful developers by forming a smaller but better organized structure to intensify the types of epistemic interactions that matter most to the OSS development. A general framework of strategic interaction including participation inequality, conversational interactivity, and cross-thread connectivity is proposed to examine its impact on knowledge sharing, and validated using 128 discussion threads from the K Desktop Environment (KDE) developer mailing list. The findings indicate that strategic interaction has expanded knowledge sharing but with the caveat that extreme concentration of development could have an opposite effect. For researchers, this study dovetails the incentive logic by proposing and validating the strategic aspects of OSS participation to better understand the collective dynamics underpinning OSS development. Practitioners can use this approach to evaluate and better support existing knowledge-sharing initiatives.
Understanding the Motivations, Participation, and Performance of Open Source Software Developers: A Longitudinal Study of the Apache Projects
Authors: Roberts Jeffrey A. , Hann Il-Horn , Slaughter Sandra A.
Published: June 2006

Understanding what motivates participation is a central theme in the research on open source software (OSS) development. Our study contributes by revealing how the different motivations of OSS developers are interrelated, how these motivations influence participation leading to performance, and how past performance influences subsequent motivations. Drawing on theories of intrinsic and extrinsic motivation, we develop a theoretical model relating the motivations, participation, and performance of OSS developers. We evaluate our model using survey and archival data collected from a longitudinal field study of software developers in the Apache projects. Our results reveal several important findings. First, we find that developers’ motivations are not independent but rather are related in complex ways. Being paid to contribute to Apache projects is positively related to developers’ status motivations but negatively related to their use-value motivations. Perhaps surprisingly, we find no evidence of diminished intrinsic motivation in the presence of extrinsic motivations; rather, status motivations enhance intrinsic motivations. Second, we find that different motivations have an impact on participation in different ways. Developers’ paid participation and status motivations lead to above-average contribution levels, but use-value motivations lead to below-average contribution levels, and intrinsic motivations do not significantly impact average contribution levels. Third, we find that developers’ contribution levels positively impact their performance rankings. Finally, our results suggest that past-performance rankings enhance developers’ subsequent status motivations.
Measurements and Monte Carlo Calculations of Gamma and Neutron Flux Spectra Inside and Behind Iron/Steel/Water Configurations
Authors: Boehmer B , Konheiser J , Noack K , Rogov A , Stephan I , Hansen W , Hinke D , Unholzer S , Grantz M , Mehner H-C
Published: June 2006

Gamma and neutron flux spectra were measured inside and behind various combined iron, steel, and water slabs, which were set up in the radial beams of the zero-power training and research reactors Ausbildungskernreaktor of the Technical University Dresden and Zittauer Lehr- und Forschungsreaktor of the University of Applied Sciences Zittau/Goerlitz. The measurements were carried out with a liquid NE-213 scintillation spectrometer in the energy ranges 0.23–10 MeV for photons and 1–20 MeV for neutrons. These experiments were simulated with the Monte Carlo transport codes mcnp-4c2 and tramo. With mcnp the point-wise energy representation of the nuclear data from endf/b-vi library, release 8, was used. For tramo effective group cross sections were prepared by means of njoy from the same data library. The paper describes the experiments and calculations and presents and compares some results.
Spallation Radiation Damage Calculations and Database: Cross-Section Discrepancies between the Codes
Authors: Lu Wei , Wechsler MS , Ferguson PD , Pitcher EJ
Published: June 2006

A radiation damage database at NCSU is described that contains, at present, cross sections for damage energy, displacements, helium, and hydrogen. For neutrons and protons at 20-3200 MeV energies, the targets include 23 target elements from Mg to U and eight practical alloys. The underlying calculations employ Bertini, ISABEL, and CEM2k intranuclear cascade models as provided within MCNPX, three level-density formulations (GCCI, HETC, and Jülich), and multistage pre-equilibrium model (MPM) on and off. The database also includes radiation damage cross sections for lower-energy neutrons and protons, as obtained from LA150, SPECTER, ENDF, and SRIM. Examples of the database contents are provided with regard to damage energy and displacement cross sections for neutrons on Al, Fe, and W. Also, neutron flux and displacement rate calculations are described for neutrons on Fe and the 316 stainless steel mercury container vessel at SNS. In addition, discrepancies between the codes are discussed.
Economic Crisis and Changes in Employment Relations in Japan and Korea
Authors: Jung EeHwan , Cheon Byung-you
Published: June 2006

This article explores changes in employment systems in Japan and Korea following the economic crisis of the 1990s. It finds significant changes as well as continuities in both countries that reflect similarities and differences.
Russia's Debate on Military-Technological Cooperation with China: From Yeltsin to Putin
Authors: Rangsimaporn Paradorn
Published: June 2006

The article examines the debate among relevant sections of Russia's foreign policy elite regarding the country's military-technological cooperation policy with China and changing views under Presidents Yeltsin and Putin. Russian views are ambivalent at best and significantly affected by the dynamics of U.S.-Russian relations.
Resistance to What? How?: Stalled social movements in Cancun
Authors: KRAY CHRISTINE A.
Published: June 2006

This paper explores the utility and futility of the concept of resistance in relationship to urban popular movements in Cancun. While Cancun has become the most popular tourist destination in Mexico, the city is characterized by severe inequalities and neighborhood segregation, the legacy of city planning. Urban settler movements have organized to pressure the city and state governments for land for purchase, public works, and services; yet the power of these movements has been curtailed by government strategies of co‐optation, orchestrated enthusiasm, and the bureaucratization of resistance. Many city residents expressed doubts that democratic elections and settler movements could ever successfully ameliorate their condition of poverty.
Expectation in Melody: The Influence of Context and Learning
Authors: Pearce Marcus T. , Wiggins Geraint A.
Published: June 2006

The Implication-Realization (IR) theory (Narmour, 1990) posits two cognitive systems involved in the generation of melodic expectations: The first consists of a limited number of symbolic rules that are held to be innate and universal; the second reflects the top-down influences of acquired stylistic knowledge. Aspects of both systems have been implemented as quantitative models in research which has yielded empirical support for both components of the theory (Cuddy & Lunny, 1995; Krumhansl, 1995a, 1995b; Schellenberg, 1996, 1997). However, there is also evidence that the implemented bottom-up rules constitute too inflexible a model to account for the influence of the musical experience of the listener and the melodic context in which expectations are elicited. A theory is presented, according to which both bottom-up and top-down descriptions of observed patterns of melodic expectation may be accounted for in terms of the induction of statistical regularities in existing musical repertoires. A computational model that embodies this theory is developed and used to reanalyze existing experimental data on melodic expectancy. The results of three experiments with increasingly complex melodic stimuli demonstrate that this model is capable of accounting for listeners’ expectations as well as or better than the two-factor model of Schellenberg (1997).
An Inverse Association between Serum Gamma Glutamyl Transpeptidase Activity and Breslow's Lifestyle Index; Its Practical Application for Screening of Subjects with Unhealthy Lifestyles
Authors: Yokoyama Hirokazu , Ohgo Hideki , Hirose Hiroshi , Moriya Susumu , Hibi Toshifumi , Saito Ikuo
Published: June 2006

An Inverse Association between Serum Gamma Glutamyl Transpeptidase Activity and Breslow's Lifestyle Index; Its Practical Application for Screening of Subjects with Unhealthy Lifestyles: Hirokazu Yokoyama,et al.Health Center, School of Medicine, Keio University—We examined whether serum γGTP activity (γGTP) is associated with Breslow's lifestyle index and whether it could be used as a tool to detect subjects with unhealthy lifestyles. To that effect, 724 male Japanese workers excluding patients suffering from hepatitis virus infection, autoimmune liver diseases and apparently active bile duct diseases were cross‐sectionally examined. γGTP was inversely associated with the total score of Breslow's index for all subjects (λ=30.643) and in subjects aged 40 or more (λ=37.073). The association was consistent even after adjustments of subjects’ ages and levels of triglycerides, total cholesterol and uric acid (p=0.0001). Among the seven lifestyle factors comprising Breslow's index, improper habits of drinking (p<0.0001), smoking (p=0.0204), exercise (p=0.0189) and body weight control (p<0.0001), were associated with increased γGTP. Even in a survey in which subjects who had proper habits of drinking and body weight control were selectively examined, improper habits of smoking and exercise still tended to be associated with increased γGTP. Receiver operating characteristic curves indicated that γGTP was beneficial for detecting subjects who scored two or less on Breslow's index, at least in subjects aged 40 or more. γGTP was associated with insulin resistance level estimated by the homeostasis model assessment (p<0.0001), which was inversely associated with Breslow's index (p=0.0040). γGTP could be used as an objective substitute of Breslow's index, allowing us to identify subjects with low scores on Breslow's index, at least after sorting subjects properly. Such screening would enable interventions to correct subjects’ unhealthy lifestyles, helping to solve lifestyle‐related disease issues.