bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural complexity of chemical recognition cues affects the perception of group membership in the ants Linephithema humile and Aphaenogaster cockerelli
Authors: Greene Michael J. , Gordon Deborah M. 
Published: February 2007

SUMMARY
Hydrocarbon profiles on the cuticle of social insects act as multi-component recognition cues used to identify membership in a species, a colony or, within colonies, cues about its reproductive status or task group. To examine the role of structural complexity in ant hydrocarbon recognition cues, we studied the species recognition response of two ant species, Linepithema humile and Aphaenogaster cockerelli, and the recognition of conspecifics by L. humile. The cuticular hydrocarbons of ants are composed of molecules of varying chain lengths from three structural classes, n-alkanes, methyl-branched alkanes and n-alkenes. We employed species recognition bioassays that measured the aggressive response of both species of ants to mixtures of hydrocarbon classes, single structural classes of hydrocarbons (n-alkanes,methyl-branched alkanes and n-alkenes), and controls. The results showed that a combination of at least two hydrocarbon structural classes was necessary to elicit an aggressive species recognition response. Moreover, no single class of hydrocarbons was more important than the others in eliciting a response. Similarly, in the recognition of conspecifics, Linepithema humile did not respond to a mixture of n-alkane cuticular hydrocarbons presented alone, but supplementation of nestmate hydrocarbon profiles with the n-alkanes did elicit high levels of aggression. Thus both L. humile and A. cockerelli required mixtures of hydrocarbons of different structural classes to recognize species and colony membership. It appears that information on species and colony membership is not in isolated components of the profile, but instead in the mixture of structural classes found in cuticular hydrocarbon profiles.
Slow dehydration promotes desiccation and freeze tolerance in the Antarctic midgeBelgica antarctica
Authors: Hayward Scott A. L. , Rinehart Joseph P. , Sandro Luke H. , Lee Richard E. , Denlinger David L. 
Published: February 2007

SUMMARYAdaptations to low moisture availability are arguably as important as cold resistance for polar terrestrial invertebrates, especially because water, in the form of ice, is biologically inaccessible for much of the year. Desiccation responses under ecologically realistic soil humidity conditions– those close to the wilting points of plants [98.9% relative humidity(RH)] – have not previously been examined in polar insect species. In the current study we show that, when desiccated at 98.2% RH, larvae of the Antarctic midge Belgica antarctica are more tolerant of dehydration than larvae desiccated at lower humidities (75% RH), and develop an increased tolerance to freezing. The slow rate of desiccation at this high RH enabled more than 50% of larvae to survive the loss of &gt;75% of their osmotically active water (OAW). Survival rates were further increased when rehydration was performed at 100% RH, rather than by direct contact with water. Two days at 98.2% RH resulted in a ∼30% loss of OAW, and dramatically increased the freeze tolerance of larvae to –10 and –15°C. The supercooling point of animals was not significantly altered by this desiccation treatment,and all larvae were frozen at –10°C. This is the first evidence of desiccation increasing the freeze tolerance of a polar terrestrial arthropod. Maximum water loss and body fluid osmolality were recorded after 5 days at 98.2% RH, but osmolality values returned to predesiccated levels following just 1 h of rehydration in water, well before all the water lost through desiccation had been replenished. This suggests active removal of osmolytes from the extracellular fluids during the desiccation process, presumably to intracellular compartments. Heat-shock proteins appear not to contribute to the desiccation tolerance we observed in B. antarctica. Instead, we suggest that metabolite synthesis and membrane phospholipid adaptation are likely to be the underpinning physiological mechanisms enhancing desiccation and cold tolerance in this species.
Transition Metal-Catalyzed Organometallic Reactions that Have Revolutionized Organic Synthesis
Authors: Negishi Ei-ichi 
Published: February 2007

Abstract
The Pd- or Ni-catalyzed cross-coupling reactions of organometals containing Zn, Al, Zr, and B as well as related reactions of Mg and several other metals collectively represent the most widely applicable organic skeleton construction method discovered and developed over the past several decades, allowing the synthetic chemists to synthesize practically all types of organic compounds. Some of the seminal and critically important discoveries and early developments in the 1970s as well as their current scope (Tables 2 and 3) are briefly discussed. Some of the notable discoveries and developments include (1) identification of superior properties of Pd relative to Ni, (2) the broad scope of Pd- or Ni-catalyzed cross-coupling with respect to metal counter cations including Zn, Al, Zr, B, and Mg, (3) the hydrometallation–Pd-catalyzed cross-coupling tandem processes for selective syntheses of alkenes, dienes, oligoenes, and oligoenynes, (4) double metal catalysis involving Pd or Ni and added metal compounds containing Zn, In, Li, and others, and (5) realization of high turnover numbers (≥103–105) through the use of chelating phosphines, such as DPEphos and dppf. In these reactions, the metal counter cations in organometals and Pd or Ni are to work successively via transmetallation. The Zr-catalyzed alkyne carboalumination and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction) have provided efficient and selective routes to methyl-branched (E)-trisubstituted alkenylalanes and 2-substituted chiral alkylalanes, respectively. These reactions provide two additional examples of prototypical transition metal-catalyzed organometallic reactions. Significantly, they can be readily combined with the Pd- or Ni-catalyzed cross-coupling for the synthesis of trisubstituted alkenes embracing a wide variety of natural products, such as terpenoids, carotenoids, and others, as well as various chiral organics including deoxypolypropionates and saturated terpenoids. The Zr-catalyzed alkyne carboalumination has been applied to the synthesis of well over 100 complex natural products (Table 4), while the ZACA reaction has been transformed from a mere scientific novelty to a full-fledged asymmetric synthetic method that is catalytic in both transition metal (Zr) and chiral auxiliaries through a series of breakthroughs (Schemes 12–17).
A Helmeted Dialkylsilylene
Authors: Kira Mitsuo , Iwamoto Takeaki , Ishida Shintaro 
Published: February 2007

Abstract
Structural characteristics, spectroscopic properties, and unique reactions of a helmeted dialkylsilylene, 2,2,5,5-tetrakis(trimethylsilyl)silacyclopentane-1,1-diyl, that was synthesized as the first isolable dialkylsilylene and its application to the synthesis of novel silicon unsaturated compounds are surveyed. The silylene was found to be the least electronically perturbed among known stable silylenes by 29Si NMR and UV–vis spectroscopies. The silylene reacts not only with well-known trapping reagents for transient silylenes, such as alcohols, triethylsilane, and 2,3-dimethylbutadiene, but also with less reactive haloalkanes and halosilanes to give the corresponding adducts. One-electron reduction of the silylene using alkali metals affords the corresponding radical anion as a relatively persistent species at low temperatures in solution. Irradiation of the silylene using visible light generates a singlet excited state with a lifetime of 80.5 ns, which reacts with various aromatic compounds and alkenes to give the corresponding silepins and siliranes in a highly regio- and stereoselective manner. The silylene is utilized for the synthesis of unique silicon unsaturated compounds, such as Si=X doubly bonded compounds (X = S, Se, Te, C=NR, etc.), a trisilaallene, a 1,3-disilagermaallene, and silylene transition-metal complexes.
Structural-Based Engineering for Transferases to Improve the Industrial Production of 5′-Nucleotides
Authors: Suzuki Ei-ichiro , Ishikawa Kohki , Mihara Yasuhiro , Shimba Nobuhisa , Asano Yasuhisa 
Published: February 2007

Abstract
The existence of a flexible region for substrate recognition by an enzyme was first discovered through a structure comparison study among ribonuclease T1–related molecules, including intact molecules, intact molecules complexed with 2′-guanylic acid (GMP), and carboxymethylated molecules complexed with 2′-GMP. Next, it was demonstrated that transglutaminase activity could be enhanced by identifying the flexible residues that affect the active site using nuclear magnetic resonance. Finally, such an approach was used to increase the production of 5′-inosinic acid (5′-IMP) and 5′-GMP. The enzyme is a nonspecific acid phosphatase with pyrophosphate-nucleoside phosphotransferase activity that is C-5′ position-selective. The crystal structure of G74D/I153T with a reduced KM is virtually identical to that of the wild type, and neither of the side chains that were introduced Asp74 and Thr153, directly interact with the nucleoside, although both residues are situated near a potential nucleoside binding site. In addition, the two regions around residues 70 and 140 have the most flexible conformational rearrangement upon phosphate analogue binding. On the basis of three-dimensional (3D) structural information, some practical, high-performance enzymes for 5′-nucleotides production were discovered, and new varieties of microorganisms were developed.
Luminescent Platinum Complexes Having Sensing Functionalities
Authors: Kato Masako 
Published: February 2007

Abstract
Square-planar platinum(II) complexes often exhibit intense color and luminescence when they are stacked via self-assembly or bridging by ligands. The origin of the color and luminescence are the metal–metal electronic interactions, and thus, remarkable changes in color (i.e., chromism) are expected by controlling the Pt···Pt interactions. The molecular arrangement of the assembled complex systems is sensitive to environmental factors such as temperature, pressure, solvent, and vapor. This account focuses on the sensing functionalities of luminescent platinum(II) complexes with 2,2′-bipyridine or its derivatives toward their environment. Especially, luminescence changes that are induced by the vapor molecules will be examined from the viewpoint of chemical sensing. The vapochromic behavior and structural aspects of the mononuclear and dinuclear platinum(II) complexes are discussed.
Organic Nanoparticles of Cyanine Dye in Aqueous Solution
Authors: Ou Zhong-min , Yao Hiroshi , Kimura Keisaku 
Published: February 2007

Abstract
Ion-based organic dye nanoparticles ranging from tens to hundreds of nanometers have been prepared in aqueous solution. The synthetic approach is based on “ion-association” (hydrophobic ion-pair formation) in water between the dye cation pseudoisocyanine (PIC) and the anion tetraphenylborate (TPB) or tetrakis(4-fluorophenyl)borate (TFPB) ion. Size tuning of spherical and amorphous PIC nanoparticles was accomplished by varying the molar ratio (ρ) of the loaded anion to the dye cation. Electrophoretic characterization revealed that the increase in surface adsorption of anions onto PIC particles brings about an increase in the negative surface charge density, causing a reduction in the surface tension and the mean size of nanoparticles. We found that the optical absorption properties of the PIC nanoparticles exhibited (i) matrix dependence, that is, the 0–0 band position of the PIC chromophore within similar-sized nanoparticles was dependent on the type of counter anions used, and (ii) size dependence, i.e., the 0–0 band position of the PIC chromophore was dependent on the mean nanoparticle diameter when the particles were prepared using the same counter anion.
DFT Calculations and IR Studies on 2-Hydroxy-1,4-naphthoquinone and Its 3-Substituted Derivatives
Authors: Satoh Takehiko , Tsuji Takemasa , Matsuda Hiroko , Sudoh Susumu 
Published: February 2007

Abstract
The carbonyl stretching vibrations of the title compounds were studied using DFT calculations at the B3LYP/6-311G** level and the IR spectra in terms of the intramolecular hydrogen bond (H-bond). Two types of H-bond systems were examined: type I in which the H-atom of the OH group points towards to neighboring carbonyl oxygen atom, and type II in which the H-atom points away. The results of the DFT calculations show that the IR spectra of 2-hydroxy-1,4-naphthoquinone (1), 3-chloro-2-hydroxy-1,4-naphthoquinone (2), 3-bromo-2-hydroxy-1,4-naphthoquinone (3), and 2-hydroxy-3-iodo-1,4-naphthoquinone (4) in CCl4, are well explained by the assumption of the two types of H-bond systems.
Control of Coordination and Luminescence Properties of Lanthanide Complexes Using Octadentate Oligopyridine-Amine Ligands
Authors: Wada Atsushi , Watanabe Masayuki , Yamanoi Yoshinori , Nankawa Takuya , Namiki Kosuke , Yamasaki Mikio , Murata Masaki , Nishihara Hiroshi 
Published: February 2007

Abstract
Lanthanide complexes with linear and cyclic octadentate oligopyridine-amine ligands were synthesized, and their molecular structures were determined by single-crystal X-ray crystallography. All of the complexes had a distorted capped square antiprism (CSAP) geometry, and the coordination environments of lanthanide complexes were more distorted for the complexes with the linear ligand than those with the cyclic ligand. The Eu3+ and Tb3+ complexes showed intense luminescence due to energy transfer from the ligand to the metal center (antenna effect). The Eu3+ complexes with the linear ligand showed more intense emissions, which were attributed to the 5D0 → 7F2 transition, than the complex with the cyclic ligand in acetonitrile, which can be attributed to the distortion in the coordination environments. In contrast, the coordination of water molecules to Eu3+ and Tb3+ ions was strongly prevented because the metal ions were surrounded by the cyclic ligand, resulting in intense luminescence in water. These results indicate that the coordination environments of lanthanide complexes, and thus the luminescence properties, can be controlled by tuning the geometrical structures of polydentate ligands.
Hydrogen Bond Donor Ability α2H Is a Good Index for Finding an Appropriate Color Developer for the Molecular Design of Functional Thermal Paper
Authors: Kawasaki Kazunori , Sakakibara Kazuhisa 
Published: February 2007

Abstract
Thermal paper, which is comprised of sulfonylurea molecule R1SO2NH–CO–NH–R2 (color developer) and the leuco-dye, can develop strong black color, and the developed color is durable. This is because sulfonylurea functional group has sufficient hydrogen bond donor ability to stabilize a π-delocalized carbocation generated from the leuco-dye due to heat-induced lactone ring opening. Thus, the color-developing complex (CDC) that appears can be stabilized by hydrogen-bond formation between two N–H bonds of the sulfonylurea and the carboxylate anion from the leuco-dye. The hydrogen bond donor ability of the color developer can be evaluated in terms of the α2H parameter proposed by Abraham. 1H NMR chemical shift values of the N–H protons in the sulfonylurea and HPLC retention times of the sulfonylurea on a silica column show a good correlation with the α2H parameter values. The essential factors necessary for the sulfonylurea to give rise to high color developing by forming a stable hydrogen-bond complex are also discussed on the basis of the structure and the electronic properties of the sulfonylureas.
Total Synthesis and Cytotoxicity of (+)- and (−)-Goniodiol and 6-epi-Goniodiol. Construction of α,β-Unsaturated Lactones by Ring-Closing Metathesis
Authors: Nakashima Katsuyuki , Kikuchi Naoki , Shirayama Daisuke , Miki Takuo , Ando Kazuhiro , Sono Masakazu , Suzuki Shinya , Kawase Masaki , Kondoh Masuo , Sato Masao , Tori Motoo 
Published: February 2007

Abstract
(+)-Goniodiol, a potent and selective cytotoxin, and (−)-6-epi-goniodiol, as well as their enantiomers, have been synthesized starting from cinnamyl alcohol. The key steps of the synthesis were Sharpless asymmetric epoxidation and cyclization of an acrylate derivative using ring-closing metathesis reaction. The cytotoxicity of both enantiomers of goniodiol and 6-epi-goniodiol against HL-60 cells was examined.
Electrochemical A-Ring Bromination of Estrogens
Authors: Damljanovic Ivan , Vukicevic Mirjana , Vukicevic Rastko D 
Published: February 2007

Abstract
A-ring bromination of estrogens has been achieved by constant current electrolysis of the solutions of these substrates and Et4NBr in appropriate solvents. Thus, electrolysis consuming 2 F mol−1 charge gave mixtures of 2- and 4-estrogens (1:1.1–2.5; up to 97%), whereas 4 F mol−1 charge experiments yielded 2,4-dibromoestrogens as the sole products.
Novel Oligomers of 9,9-Dialkylated Fluorenes for Thermally Stable Hole-Transport Materials in OLEDs
Authors: Kimura Makoto , Kurata Toshihiko , Sawaki Yasuhiko , Toba Yasumasa , Enokida Toshio , Takagi Katsuhiko 
Published: February 2007

Abstract
Using 9,9-dialkyl-functionalized fluorenes as monomers, novel fluorene-based oligomers were prepared in order to improve the thermal stability of a typical hole-transport material (HTM), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), in organic light emitting diodes (OLEDs). 2,7-Bis(diphenylamino)fluorene was utilized as a TPD unit throughout the present synthetic work. 9,9-Bis(2-methylallyl)fluorene and its TPD congener underwent a new cyclopolymerization reaction affording six-membered oligomers under acid catalysis with p-toluenesulfonic acid. Intermolecular Suzuki coupling of a 9,9-bis(p-bromobenzyl)fluorene analogue with the corresponding bis-boronate afforded a new oligomer containing the TPD substructure. These oligomers (3 and 6) for use as HTMs have high glass-transition temperatures (Tg’s) (147 and 167 °C, respectively); the values are much higher than the Tg for TPD (63 °C). These materials are soluble in organic solvents to allow easy processing for preparing layered devices, though their electroluminescent performances were lower than that of the single molecule TPD.
Hydrothermal Synthesis of Fine NaTaO3 Powder as a Highly Efficient Photocatalyst for Overall Water Splitting
Authors: Lee Yungi , Watanabe Tomoaki , Takata Tsuyoshi , Hara Michikazu , Yoshimura Masahiro , Domen Kazunari 
Published: February 2007

Abstract
A fine powder of sodium tantalum(V) trioxide as single-phase perovskite NaTaO3 has been successfully prepared by hydrothermal synthesis through the reaction of a sodium hydroxide solution and ditantalum pentaoxide powder at low temperature (373–473 K). The NaTaO3 powder has high photocatalytic activity for both H2 evolution (8.0 mmol h−1) and O2 evolution (4.1 mmol h−1), which is attributed to the high surface area, small particle size and high crystallinity of the powder catalyst.
Synthesis and Crystallization of Hexagonal Boron Nitride in Liquid Sodium Amide
Authors: Gu Yunle , Zheng Mingtao , Xu Zilin , Liu Yingliang 
Published: February 2007

Abstract
Hexagonal boron nitride was synthesized from MB6 (M = Ca and La) in liquid sodium amide at 600 °C. The as-synthesized boron nitride powders were composed of sub-micrometer-sized triangles and hexagons.
Admission Temperature of Low Birth Weight Infants: Predictors and Associated Morbidities
Authors: Laptook Abbot R. , Salhab Walid , Bhaskar Brinda ,   and the Neonatal Research Network
Published: February 2007

BACKGROUND. There is a paucity of information on the maintenance of body temperature at birth for low birth weight infants.OBJECTIVES. We examined the distribution of temperatures in low birth weight infants on admission to the NICUs in the Neonatal Research Network centers and determined whether admission temperature was associated with antepartum and birth variables and selected morbidities and mortality.METHODS. Infants without major congenital anomalies born during 2002 and 2003 with birth weights of 401 to 1499 g who were admitted directly from the delivery room to the NICU were included. Bivariate associations between antepartum/birth variables and admission temperature and selected morbidities/mortality and admission temperature were examined, followed by multivariable linear or logistic regressions to detect independent associations.RESULTS. There were 5277 study infants and the mean (±SD) birth weight and gestational age were 1036 ± 286 g and 28 ± 3 weeks, respectively. The distribution of admission temperatures was 14.3% at &lt;35°C, 32.6% between 35 and 35.9°C, 42.3% between 36 and 36.9°C, and 10.8% at ≥37°C. The estimate of birth weight on admission temperature with and without intubation was +0.13°C and +0.04°C per 100-g increase in birth weight, respectively. The mean admission temperature for each center varied from 1.5°C below to 0.3°C above a reference center. On adjusted analyses, admission temperature was inversely related to mortality (28% increase per 1°C decrease) and late-onset sepsis (11% increase per 1°C decrease) but not to intraventricular hemorrhage, necrotizing enterocolitis, or duration of conventional ventilation.CONCLUSIONS. Preventing decreases in temperature at birth among low birth weight infants remains a challenge. Associations with intubation and center of birth suggest that assessment of temperature control for infants intubated in the delivery room may be beneficial. Whether the admission temperature is part of the casual path or a marker of mortality needs additional study.
Fast times and easy questions: the effects of age, experience and question complexity on web survey response times
Authors: Yan Ting , Tourangeau Roger 
Published: February 2007

AbstractThis paper examines response times (RT) to survey questions. Cognitive psychologists have long relied on response times to study cognitive processes but response time data have only recently received attention from survey researchers. To date, most of the studies on response times in surveys have treated response times either as a predictor or as a proxy measure for some other variable (e.g. attitude accessibility) of greater interest. As a result, response times have not been the main focus of the research. Focusing on the nature and determinants of response times, this paper examines variables that affect how long it takes respondents to answer questions in web surveys. Using the survey response model proposed by Tourangeau, Rips, and Rasinski (2000), we include both item‐level characteristics and respondent‐level characteristics thought to affect response times in a two‐level cross‐classified model. Much of the time spent on processing the questions involves reading and interpreting them. The results from the cross‐classified models indicate that response times are affected by question characteristics such as the total number of clauses and the number of words per clause that probably reflect reading times. In addition, response times are also affected by the number and type of answer categories, and the location of the question within the questionnaire, as well as respondent characteristics such as age, education and experience with the Internet and with completing web surveys. Aside from their fixed effects on response times, respondent‐level characteristics (such as age) are shown to vary randomly over questions and effects of question‐level characteristics (such as types of questions and response scales) vary randomly over respondents. Copyright © 2007 John Wiley & Sons, Ltd.