bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Basis for Transition-State Stabilization in Catalytic Antibodies
Authors: Tsumuraya Takeshi , Fujii Ikuo
Published: September 2008

Antibodies elicited against rationally designed transition-state analogs catalyze a large number of reactions, including many that cannot be achieved by standard chemical methods. This account describes a detailed investigation of the molecular mechanism of catalysis in catalytic antibodies. We have investigated the biochemical properties within a panel of six hydrolytic catalytic antibodies elicited against a phosphonate transition-state analog. The transition-state analyses (kcat⁄kuncat versus Km⁄Ki) displayed a linear relationship with five antibodies, 6D9, 8D11, 4D5, 3G6, and 9C10, which have homologous primary amino acid sequences, while antibody 7C8 deviates from the linear relationship. These results suggest that the five antibodies catalyze the hydrolysis by the same reaction mechanism of transition-state stabilization and that catalytic factors other than transition-state stabilization are involved for antibody 7C8. The structure of 6D9 Fab with the transition-state analog (TSA) has been solved, showing that 6D9 binds the phosphonate of TSA by forming one hydrogen bond with HisL27d. The kinetic, structural, and thermodynamic analyses of 6D9 indicate that this antibody provides an efficient catalyst by transition-state stabilization through the hydrogen bond with HisL27d and the destabilization of the substrate. Although catalytic antibodies are still much inferior to natural enzymes in their catalytic efficiency, several aspects including the mechanism of enzyme catalysts can be faithfully mimicked. Therefore, the molecular mechanism of catalytic antibodies might provide useful insights to understanding the catalysis in enzymes.
Catalytic Behavior of Cationic Hydridoruthenium(II) Complex, [RuH(NH3)(PMe3)4]+, in H2-Hydrogenation and Transfer Hydrogenation of Imines
Authors: Kayaki Yoshihito , Ikeda Hibiki , Tsurumaki Jun-ichirou , Shimizu Isao , Yamamoto Akio
Published: September 2008

Catalytic hydrogenation under H2 and transfer hydrogenation of imines by secondary alcohols with hydridoruthenium complexes bearing PMe3 and PPh3 ligands have been examined. A cationic hydridoruthenium complex, cis-[RuH(NH3)(PMe3)4]PF6 (2), derived from cis-[RuH2(PMe3)4] (1) and NH4PF6, showed higher catalytic activity for H2-hydrogenation of N-benzylideneaniline than neutral complexes such as 1 and cis-[RuClH(PMe3)4] (6). The effectiveness of cationic hydridoruthenium species for the catalytic H2-hydrogenation of benzylideneaniline was also demonstrated by a marked increase in the yield of N-benzylaniline on treatment of 6 with AgPF6. The cationic complex 2 was applicable to catalytic transfer hydrogenation of imines with secondary alcohols even in the absence of a base. Isotope labeling experiments using deuterated alcohols revealed that the hydrogen atom bound to the α-carbon of the donor alcohol was transferred exclusively to the imine carbon and alcoholic OD was transferred to the imine nitrogen. A rapid exchange between the alcoholic proton and the hydrido ligand of 2 was also confirmed by NMR investigation using (CH3)2CHOD. On the basis of the experimental results the mechanisms of the H2-hydrogenation and transfer hydrogenation are discussed.
Gangliosides’ Inhibitory Effects on NAD Glycohydrolase: Estimating the Solvation Effect in the Physiological Environment
Authors: Ueno-Noto Kaori , Hara-Yokoyama Miki , Takano Keiko
Published: September 2008

The solvation effect was considered in order to interpret the causative factors of the differences in gangliosides’ inhibitory effects on CD38, an enzyme nicotinamide adenine dinucleotide (NAD) glycohydrolase, as well as the mechanisms by which the gangliosides recognize CD38, in the biological system. We applied the two-layered our own N-layered integrated molecular orbital and molecular mechanics (ONIOM) method as well as the supermolecule method to a large solvated system. For comparison, the conductor-like screening model (COSMO) was applied to the same system. The orbital energy of the highest occupied molecular orbital (HOMO) was correlated with the strength of the gangliosides’ inhibitory effect in both the supermolecule and ONIOM methods; this agrees with our previous results in the gas phase. Solvation only slightly affected both the structures of tandem sialic acid residues themselves and the energy profiles of HOMOs of gangliosides. These results support the previously proposed recognition mechanism, in which CD38 is likely to recognize the two phosphate groups in the substrate, NAD, as well as the two carboxyl groups in gangliosides’ tandem sialic acid residues.
Thermodynamics of Zinc(II) Complexes with N′1,N′2-Dihydroxy-N1,N2-dipyridin-2-ylethanediamidediimide in the Gas Phase
Authors: Zabardasti Abedien , Kakanejadifard Ali , Amani Saeid , Salehnassaje Maryam
Published: September 2008

Ab initio and density functional calculations were used to study the coordination and thermodynamic properties of mononuclear complexes of dimethylglyoxime (H2M), diaminoglyoxime (H2A), and (1Z,2Z)-N′1,N′2-dihydroxy-N1,N2-dipyridin-2-ylethanediamidediimide (H2L) as well as dinuclear complexes of H2L with zinc(II) at B3LYP/6-31G(d), B3LYP/6-31+G(d), and B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d) computational levels. Theoretical calculation shows that unusual O,O-coordination is a stable model for coordination of H2L to zinc(II) in the gas phase.
Effect of Internal Branching on Numbers of Monosubstituted Alkanes as Three-Dimensional Structures and as Graphs
Authors: Fujita Shinsaku
Published: September 2008

Itemized numbers of achiral and/or chiral monosubstituted alkanes (MSAs) as three-dimensional structures have been obtained by means of a newly developed method based on Fujita’s proligand method (S. Fujita, Theor. Chem. Acc.2005, 113, 73; 2005, 113, 80; 2006, 115, 37), where the itemization with respect to internal branching has been embodied by employing branching indicators (BIs), i.e., q for quaternary carbons, t for tertiary carbons, s for secondary carbons, and p for primary carbons. Each of the numbers appears as the coefficient of a branching monomial qnqtntsnspnpxk, which is contained in a generating function to characterize MSAs having nq quaternary carbons, nt tertiary carbons, ns secondary carbons, and nq quaternary carbons (k=nq+nt+ns+np). By following Fujita’s proligand method, functional equations for recursive calculations have been obtained to treat respective cases, where previous approaches without considering BIs have been extended so as to incorporate BIs with no violation of consistency. The resulting functional equations have been used to obtain generating functions which give the numbers of achiral MSAs, chiral MSAs, total (achiral and chiral) MSAs. They have been compared with the corresponding numbers of MSAs as graphs. Thereby, difference between stereoisomers (3D structures) and constitutional isomers (graphs) has been discussed on a quantitative basis.
Molecular Structure Optimization and Molecular Dynamics Using Hamiltonian Algorithm: Structure of Benzodiazepine Minor Tranquilizers—Towards Non-Empirical Drug Design—
Authors: Teramae Hiroyuki , Ohtawara Kazushige , Ishimoto Takayoshi , Nagashima Umpei
Published: September 2008

We have studied the molecular dynamics of the benzodiazepine and thienodiazepine minor tranquilizers using a Hamiltonian Algorithm (HA) combined with ab initio molecular orbital methods. The HA utilizes classical dynamics for optimization of the complicated systems. We show that the HA gives an effective search of the potential energy surfaces and we can find an energy minimum even if we start from another energy local minimum. The conformers of these minor tranquilizers are calculated after computation of the molecular dynamics. Relations between electronic states and strength of tranquilizers are studied for about 17 species of benzodiazepines and thienodiazepines which are sold in the Japanese market as minor tranquilizers. The orbital energy levels of the next highest occupied molecular orbital (next-HOMO or HOMO−1) are found to be strongly related to the strength of the tranquilizers. The simple structure–activity relationship is obtained by considering just one-electron properties, i.e., the molecular orbital energies.
Spectrophotometric Determination of Gold after Separation and Preconcentration with a Solid-Phase Extraction Method
Authors: Sorouraddin Mohammad-Hossein , Saadati Masoud
Published: September 2008

A simple, sensitive, and inexpensive method for separation and preconcentration of gold ions from aqueous solutions prior to its spectrophotometric determination is reported. The proposed method includes two procedures. In the first one, sodium 8-aminoquinoline-5-azobenzene-4′-sulfonate (SPAQ) was immobilized directly on an alumina column which adsorbed gold ions from aqueous solutions. Then, AuIII was desorbed by HCl solution, and the absorbance of the alkaline solution in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTMAB), was measured at 611 nm. In the second procedure, Au–SPAQ complex in the presence of CTMAB in alkaline media was passed through the column containing alumina (washed with nitric acid and neutralized by washing with distilled water). The complex was then desorbed with ethanol, and the absorbance was measured immediately at 611 nm. The proposed methods were applied successfully to the determination of gold in Azerbaijan ores. The relative standard deviations for five replicate determinations of 0.2 μg mL−1 AuIII for the first and second procedures were 3.01% and 2.66%, and the corresponding limits of detection were 1.37 and 3.70 μg L−1, respectively.
Substituent and Solvent Effects on Square-Planar–Tetrahedral Equilibria of Bis[4-(arylimino)pentan-2-onato]nickel(II) and Bis[1-aryl-3-(phenylimino)butan-1-onato]nickel(II) Complexes
Authors: Mori Yukie , Shirase Hitoshi , Fukuda Yutaka
Published: September 2008

Nickel(II) bis(Schiff base) complexes, NiL2 (1a–1f) and NiL′2 (2a–2e) (where L = 4-(arylimino)pentan-2-onate and L′ = 1-aryl-3-(phenylimino)butan-1-onate), exist in an equilibrium of square-planar (Sp) and tetrahedral (Td) forms in non-coordinating solvents. The Td form is more stabilized in polar solvents such as CH2Cl2 than in non-polar solvents such as toluene. Thermodynamic data were determined from temperature-dependent 1H NMR contact shift. It is suggested for 1a–1f that the oxygen atoms in Td form interact with solvent such as chloroform via hydrogen bonding. With increase in electron-donating ability of the substituents on aryl groups, the Td form becomes more favored. The free energy change roughly correlates with Hammet’s σp value. The UV–vis–NIR spectra indicated that the ligand field strength increases with the electron-donating ability of the substituents in both the Sp and Td forms. Results of DFT calculation suggest that the observed substituent effect may result from small perturbation of the metal–ligand bonding character.
Synthesis and Fluorescent Properties of a Chiral Conjugated Polymer Based on (S)-2,2′-Binaphtho-20-crown-6
Authors: Huang Hui , Miao Qian , Kang Yixiong , Huang Xiaobo , Xu Jinqian , Cheng Yixiang
Published: September 2008

Linear conjugated polymer was obtained by the polymerization of 2,3-dibutoxy-1,4-diethynylnaphthalene (M-1) and (S)-5,5′-dibromo-6,6′-dibutyl-2,2′-binaphtho-20-crown-6 (S-M-2) via Pd-catalyzed Sonogashira reaction. The conjugated polymer shows strong green-blue fluorescence due to the extended π-electronic structure between the chiral repeating unit (S)-6,6′-dibutyl-2,2′-binaphtho-20-crown-6 and the conjugated linker 2,3-dibutoxynaphthyl group via acetylene bridge. The responsive properties of the chiral polymer on K+, Pb2+, Hg2+, and AsIII were investigated by fluorescent spectra. The results show that Hg2+ and AsIII can cause effective fluorescent quenching of the polymer, whereas, K+ and Pb2+ do not produce obvious changes in the polymer fluorescence. The obvious fluorescent influence shows that the 2,2′-binaphtho-20-crown-6 moiety plays an important role in fluorescent recognition for Hg2+ and AsIII due to the effective photoinduced electron transfer (PET) and charge transfer (PCT) between the conjugated polymer backbone and receptor species.
Crystal Structures, Degree of Charge Transfer, and Non-Linear Optical Characteristics of Intramolecular Charge-Transfer Compounds: Indoline-Substituted Tricyanoquinodimethanes
Authors: Murata Tsuyoshi , Saito Gunzi , Nishimura Kazukuni , Chong Chin-Hong , Makihara Masaru , Honda Genki , Enomoto Yuichiro , Khasanov Salavat , Yamochi Hideki , Otsuka Akihiro , Kamada Kenji , Ohta Koji , Kawamata Jun
Published: September 2008

The substituent effect on the degree of intramolecular charge transfer (δ) and optical properties of donor–π–acceptor compounds comprised of 1,3,3-trimethyl-2-methyleneindoline (I1) and substituted 7,8,8-tricyanoquinodimethane (=2-(4-cyanomethylene-2,5-cyclohexadienylidene)malononitrile, 3CNQ-R, R = substituent groups) moieties were investigated (I1–3CNQ-R). In the crystal structures, I1–3CNQ-R molecules stacked on indoline and/or 3CNQ-R moieties in a head-to-tail manner to cancel their dipole moments and established segregated or mixed stack columnar motifs. The δ values of I1–3CNQ-R molecules in solid and solution states were estimated using the bond length ratio in the crystal structures, molecular orbital calculation, and the solvatochromic shift of intramolecular charge-transfer absorption, respectively, and showed significant and reasonable dependences on substituents of the 3CNQ moiety. Structural analysis revealed that molecular conformation and planarity affect the δ values of I1–3CNQ-R molecules. Molecular orbital calculations revealed that molecular (hyper)polarizabilities can be modulated by tuning δ. I1–3CNQ-R exhibited a solvatochromic shift, and the ground state changed from neutral (δ≤0.5) in less-polar solvents to ionic (δ≥0.5) in polar solvents. Two-photon absorption properties of I1–3CNQ-R showed a significant substituent effect and indicated that δ is a fundamental parameter for modulating non-linear optical properties.
Effects of Added CO2 and H2 on the Direct Decomposition of NO over BaMnO3-Based Perovskite Oxide
Authors: Iwakuni Hideharu , Shinmyou Yusuke , Yano Hiroaki , Goto Kazuya , Matsumoto Hiroshige , Ishihara Tatsumi
Published: September 2008

N2 yield on Ba0.8La0.2Mn0.8Mg0.2O3 decreased from 70% to 30% on the addition of 1% CO2, which is a much larger negative effect than that seen with O2. The CO2 negative effects are not permanent and this may result from the inhibition of NO adsorption. Co-feeding of H2 as a reductant is effective for increasing NO conversion. This suggests that the catalyst surface was covered with strongly adsorbed nitrate or nitride species which formed by adsorption of NO on oxygen formed by the decomposition of NO, and the removal of this surface species might be the most important step for the NO decomposition reaction. Co-feeding of H2 is also effective for increasing the NO decomposition activity in the presence of CO2. The reaction mechanism was studied by IR measurements which also revealed that the surface of the catalyst was covered with strongly bound nitrate species (NO3−). The addition of H2 to the reaction mixture is effective for NO3− removal and so accelerates the NO decomposition under coexistence of CO2.
Free β-Subunit of Human Chorionic Gonadotropin in Serum Is a Diagnostically Sensitive Marker of Seminomatous Testicular Cancer
Authors: Lempiäinen Anna , Stenman Ulf-Håkan , Blomqvist Carl , Hotakainen Kristina
Published: September 2008

Background: We studied whether measurement of the free β subunit of human chorionic gonadotropin (hCGβ) in serum offers additional diagnostic information compared to determination of intact hCG alone in testicular cancer.

Methods: We determined hCG and hCGβ with ultrasensitive assays in 94 serum samples obtained preoperatively, 22 samples obtained during relapse, and 3687 samples obtained during routine follow-up of 351 patients with testicular tumors.

Results: In preoperative samples, isolated increases of hCGβ were seen in 40% of the samples from seminoma patients (n = 42) and in 8% of those from patients with nonseminomatous testicular cancer (NSGCT) (n = 51). Both markers were increased in 12% of the seminoma and 71% of the NSGCT patients and were within reference intervals in 43% of the seminoma and 20% of the NSGCT patients. Specific determination of hCGβ increased the frequency of marker-positive seminomas from 17% to 57% and of marker-positive relapses from 32% to 59% (n = 22). Theoretically, about 40% of marker-positive seminomas and relapses would have been missed with an assay measuring hCG and hCGβ together. Preoperative hCG and hCGβ concentrations correlated with stage, tumor histology, and disease-related mortality. Additionally, hCGβ correlated with tumor size.

Conclusions: hCGβ is a diagnostically sensitive marker for testicular cancer. In patients with seminomatous testicular cancer, hCGβ is superior to hCG, and in some NSGCT patients it provides additional information.
A rigidity result for domains with a locally strictly convex point
Authors: Jo Kyeonghee
Published: September 2008

In this article, we investigate projective domains with a strictly convex point in the boundary and their automorphisms. We prove that ellipsoids can be characterized as follows: A domain Ω is an ellipsoid if and only if ∂Ω is locally strongly convex at some boundary point where an Aut(Ω)-orbit accumulates. We also show that every quasi-homogeneous projective domain in an affine space which is locally strictly convex at a boundary point, is the universal covering of a closed projective manifold.
On Grassmann secant extremal varieties
Authors: Ciliberto Ciro , Cools Filip
Published: September 2008

In this paper we give a sharp lower bound on the dimension of Grassmann secant varieties of a given variety and we classify varieties for which the bound is attained.
Almost del Pezzo manifolds
Authors: Jahnke Priska , Peternell Thomas
Published: September 2008

We classify projective manifolds X of dimension n ≥ 3 with nef anticanonical class and index n – 1 such that .
Projective models of K3 surfaces with an even set
Authors: Garbagnati Alice , Sarti Alessandra
Published: September 2008

The aim of this paper is to describe algebraic K3 surfaces with an even set of rational curves or of nodes. Their minimal possible Picard number is nine. We completely classify these K3 surfaces and after a careful analysis of the divisors contained in the Picard lattice we study their projective models, giving necessary and sufficient conditions to have an even set. Moreover we investigate their relation with K3 surfaces with a Nikulin involution.
Principal bundles over a smooth real projective curve of genus zero
Authors: Biswas Indranil , Huisman Johannes
Published: September 2008

Let H
0 denote the kernel of the endomorphism, defined by , of the real algebraic group given by the Weil restriction of . Let X be a nondegenerate anisotropic conic in . The principal -bundle over the complexification defined by the ample generator of Pic(), gives a principal H
0-bundle over X through a reduction of structure group. Given any principal G-bundle EG
over X, where G is any connected reductive linear algebraic group defined over ℝ, we prove that there is a homomorphism such that EG
is isomorphic to the principal G-bundle obtained by extending the structure group of using .

The tautological line bundle over the real projective line and the principal -bundle together give a principal -bundle F on , Given any principal G-bundle EG
over , where G is any connected reductive linear algebraic group defined over ℝ, we prove that there is a homomorphism such that EG
is isomorphic to the principal G-bundle obtained by extending the structure group of F using .
Nitric oxide and sphingolipids: mechanisms of interaction and role in cellular pathophysiology
Authors: Perrotta Cristiana , De Palma Clara , Clementi Emilio
Published: September 2008

Nitric oxide is a short-lived messenger with pleiotropic roles in the regulation of cell patho-physiological processes, including survival, death, proliferation and differentiation. Increasing evidence over the last few years has shown that nitric oxide effects in apoptosis, growth and differentiation originate in significant part from its interplay with signalling members of the sphingolipid family. In many cell types belonging to different lineages, nitric oxide and sphingolipids interact in two-way pathways leading to regulation of the activity and expression of enzymes involved in each other's signalling events. These crosstalk signalling events involve various sphingolipids, with key roles for ceramide and sphingosine-1-phosphate, and signal transduction molecules downstream of nitric oxide, with cyclic GMP as a main player. The biological implications of some of these interactions are now being understood. The best-characterised so far, the mutual regulation of sphingomyelinases and endothelial nitric oxide synthase, acts as a tuning system in crucial patho-physiological processes such as inflammation, proliferation and cell death.
Regulation of human tissue kallikrein-related peptidase expression by steroid hormones in 32 cell lines
Authors: Shaw Julie L.V. , Diamandis Eleftherios P.
Published: September 2008

Human tissue kallikrein-related peptidases (KLK), which are secreted serine proteases, are encoded by 15 genes located on chromosome 19q13.4. Previous studies have shown thatKLKexpression is regulated by steroid hormones and many KLKs are dysregulated in hormone-dependent malignancies. Some KLKs are proposed biomarkers for these cancers. We have characterized KLK hormonal regulation patterns using a large number of human cell lines. KLK levels were quantified in supernatants from 32 cell lines, each subjected to four hormonal stimulations (dexamethasone, norgestrel, dihydrotestosterone or estradiol), using ELISAs. Cell lines included breast, prostate, ovarian, lung, pancreatic, colon, and cervical cancer cells, T-lymphocytes, keratinocytes and a non-cancerous epithelial breast cell line. KLKs were regulated in several cell lines not previously studied, such as keratinocytes (KLK5, 6, and 7), ovarian cancer (KLK5 and 9) and cervical cancer (KLK3, 5, 6, 7, 8, 10, 11, and 13) cells. Many KLKs were regulated by the synthetic glucocorticoid dexamethasone; specifically, KLK5, 6, 8, 10 and 11 were upregulated in several breast cancer cell lines and downregulated in several cervical cancer cell lines. Knowledge of KLK hormonal regulation patterns will help to shed further light on their potential use as biomarkers and therapeutic targets for hormone-related malignancies.
Ceramide in bacterial infections and cystic fibrosis
Authors: Grassmé Heike , Becker Katrin Anne , Zhang Yang , Gulbins Erich
Published: September 2008

Ceramide is formed by the activity of sphingomyelinases, by degradation of complex sphingolipids, reverse ceramidase activity or de novo synthesized. The formation of ceramide within biological membranes results in the formation of large ceramide-enriched membrane domains. These domains serve the spatial and temporal organization of receptors and signaling molecules. The acid sphingomyelinase-ceramide system plays an important role in the infection of mammalian host cells with bacterial pathogens such as Neisseria gonorrhoeae, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium and Pseudomonas aeruginosa. Ceramide and ceramide-enriched membrane platforms are also involved in the induction of apoptosis in infected cells, such as in epithelial and endothelial cells after infection with Pseudomonas aeruginosa and Staphylococcus aureus, respectively. Finally, ceramide-enriched membrane platforms are critical regulators of the release of pro-inflammatory cytokines upon infection. The diverse functions of ceramide in bacterial infections suggest that ceramide and ceramide-enriched membrane domains are key players in host responses to many pathogens and thus are potential novel targets to treat infections.
Advances in defect characterisation using long-range ultrasonic testing of pipes
Authors: Catton P , Mudge P , Balachandran W
Published: September 2008

Ultrasonic guided waves have been used for the rapid screening of pipes and pipelines for corrosion over the past 10 years. The hardware used in guided wave testing has improved since the early equipment, and now has up to 24 transmit-receive channels. This added capability has facilitated
step changes in the way these tests are conducted, and has led to the introduction of better phased array focusing of guided waves and greatly enhanced post-processing techniques.The focusing technique provides increased sensitivity to defects and information about their circumferential
position and extent. However, it relies on defects being detected in the initial screening test to identify the locations at which to apply the focused excitation.This paper presents an enhanced signal display technique that presents the operator with more information from the initial
screening test, helping to prevent false negatives and to choose effective focal positions. A defect characterisation method is then presented that convolves information from this focused inspection with the information from the initial screening test to give defects a severity rating. Defect
severity and position can be assessed with a higher degree of confidence than was previously achievable. The process has been tested under field conditions and has been shown to give good results.
An investigation to determine the location of fatigue crack initiation sites from ultrasonic images of corrosion
Authors: Birt E A , Nelson L J
Published: September 2008

Future corrosion control management on aircraft is planning to move from a Find-and-Fix approach to an Identify-and-Manage approach. Central to this change is the development of suitable life-prediction models that can be used to predict the effects of corrosion on structural integrity.
This new approach requires NDE methods that can detect, characterise and monitor the corrosion damage. If the corrosion pit initiating the fatigue crack which leads to failure can be reliably identified in advance, existing life-prediction models can be employed for life prediction by using
the dimensions of the corrosion pit as the initial flaw. This study has analysed 50 MHz ultrasonic amplitude C-scan images of pitting and crevice corrosion specimens to determine a parameter whose location in the image correlates with the point of failure of the specimen. Texture analysis
was applied to ultrasonic amplitude images of corrosion using three texture filters, namely range, standard deviation and entropy. In addition, Laplacian filtering was applied to the images. The parameters of the filtered images chosen to correlate with the location of the point of failure
were maximum range, maximum standard deviation, maximum entropy and maximum and minimum Laplacian values. It was found that the location of these parameters did not consistently coincide with the location of the corrosion pit that initiated failure.
Effect of Wettability on High-Velocity Coefficient in Two-Phase Gas/Liquid Flow
Authors: Noh Myeong , Firoozabadi Abbas
Published: September 2008

Gas-well productivity is affected by two distinct mechanisms: liquid blocking and high-velocity flow in two-phase flow. The former has been studied extensively recently, but the understanding of the latter is limited. High-velocity gas flow in single phase has been studied thoroughly by a large number of authors. Despite the fact that high-velocity coefficient in the presence of an immobile and a mobile liquid phase is much higher than that in single phase, only a handful of studies have been made on the subject. In this work, we have measured the high-velocity coefficient, A in steady-state two-phase gas/liquid flow. The results are presented as a function of liquid relative permeability and liquid saturation. In our measurements, the wetting state is varied by the treatment with a fluorochemical compound. Then, the effect of wettability on the high-velocity coefficient in two-phase flow is investigated. Results show that when the liquid is strongly wetting, the high-velocity coefficient increases approximately 270-fold in water/gas two-phase flow. However, our data show a systematic reduction of high-velocity coefficients for the altered wetting state in two-phase flow. We present measurements of the velocity coefficients in single-phase flow and two-phase flow, for both oil/gas and water/gas flow and strong liquid-wetting and altered-wetting states. On the basis of our measurements, we conclude that the treatment of the wellbore region can result in significant improvement in well deliverability from the large reduction of high-velocity coefficients.
A Permeability Model for Coal and Other Fractured, Sorptive-Elastic Media
Authors: Robertson Eric P. , Christiansen Richard L.
Published: September 2008

This paper describes the derivation of a new equation that can be used to model the permeability behavior of a fractured, sorptive-elastic medium, such as coal, under variable stress conditions. The equation is applicable to confinement pressure schemes commonly used during the collection of permeability data in the laboratory. The model is derived for cubic geometry under biaxial or hydrostatic confining pressures. The model is designed to handle changes in permeability caused by adsorption and desorption of gases onto and from the matrix blocks in fractured media. The model equations can be used to calculate permeability changes caused by the production of methane (CH4) from coal as well as the injection of gases, such as carbon dioxide, for sequestration in coal. Sensitivity analysis of the model found that each of the input variables can have a significant impact on the outcome of the permeability forecast as a function of changing pore pressure; thus, accurate input data are essential. The permeability model also can be used as a tool to determine input parameters for field simulations by curve fitting laboratory-generated permeability data. The new model is compared to two other widely used coal-permeability models using a hypothetical coal with average properties.
A New Model of Trapping and Relative Permeability Hysteresis for All Wettability Characteristics
Authors: Spiteri Elizabeth J. , Juanes Ruben , Blunt Martin J. , Orr Franklin M.
Published: September 2008

The complex physics of multiphase flow in porous media are usually modeled at the field scale using Darcy-type formulations. The key descriptors of such models are the relative permeabilities to each of the flowing phases. It is well known that, whenever the fluid saturations undergo a cyclic process, relative permeabilities display hysteresis effects.

In this paper, we investigate hysteresis in the relative permeability of the hydrocarbon phase in a two-phase system. We propose a new model of trapping and waterflood relative permeability, which is applicable for the entire range of rock wettability conditions. The proposed formulation overcomes some of the limitations of existing trapping and relative permeability models. The new model is validated by means of pore-network simulation of primary drainage and waterflooding. We study the dependence of trapped (residual) hydrocarbon saturation and waterflood relative permeability on several fluid/rock properties, most notably the wettability and the initial water saturation. The new model is able to capture two key features of the observed behavior: (1) non-monotonicity of the initial-residual curves, which implies that waterflood relative permeabilities cross; and (2) convexity of the waterflood relative permeability curves for oil-wet media caused by layer flow of oil.
Fungicide Application Timing and Row Spacing Effect on Soybean Canopy Penetration and Grain Yield
Authors: Hanna Shane O. , Conley Shawn P. , Shaner Gregory E. , Santini Judith B.
Published: September 2008

Foliar diseases, such as soybean rust (Phakopsora pachyrhizi) can cause severe defoliation and yield loss in soybean [Glycine max (L.) Merr.] and can be managed with an effective fungicide applied during the reproductive growth stages. The impact of soybean row spacing and fungicide application timing on canopy penetration and grain yield are unknown. The objectives of this experiment were (i) to quantify the impact of crop row spacing and spray application timing on penetration and coverage with a fungicide and (ii) to quantify the impact of sprayer wheel traffic during fungicide application on crop yield. The experiment was a split plot design with three replications conducted at the Northeast, Southeast, and Davis–Purdue Agricultural Centers (NEPAC, SEPAC, DPAC) in 2005 and 2006. The whole‐plot treatments were crop row spacing (19, 38, and 76 cm) and fungicide (azoxystrobin + propiconazole) [(methyl (E)‐2‐[2‐[6‐(2‐cyanophenoxy)pyrimidin‐4‐yl]oxyphenyl]‐3‐methoxy‐prop‐2‐enoate) + (1‐[[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2‐yl]methyl]‐1,2,4‐triazole)] application timing (unsprayed or applications at growth stages R1, R3, R5, R3 + R5, or R1 + R3 + R5). Spray canopy coverage was quantified at 30‐cm increments within the soybean canopy. Crop row spacing affected spray canopy coverage at the R3 growth stage at the NEPAC location only. Application timing did not affect canopy coverage or spray penetration. Coverage decreased with depth in the canopy. Grain yield averaged 9% greater in the 19‐ and 38‐cm row spacing than in the 76‐cm row spacing. Fungicide application timing did not influence yield. Our research shows that fungicide application timing should not influence row spacing decisions. Growers should consider the effects of wheel‐track damage when planning spray applications during the reproductive growth stages of soybean.
Graphic Analysis of Trait Relations of Rapeseed Using the Biplot Method
Authors: Dehghani Hamid , Omidi Heshmat , Sabaghnia Naser
Published: September 2008

Interest in growing winter rapeseed (Brassica napus L.) in Iran is increasing due to its potential returns relative to other oilseed crops. The objectives of this study were (i) to investigate the interrelationships among different traits of winter rapeseed and (ii) to determine the effects of sowing date and variety on the seed yield and other traits of winter rapeseed with application of the biplot methodology in visualizing agronomic research data. Four winter rapeseed varieties were grown on three sowing dates during 2 yr. The results showed that variety 1 (SLM046) produced maximum seed yield and oil content in the second (21 September) and the third sowing dates (1 October). Thousand seed weight was positively and significantly associated with seed yield and the number of pods per plant, but oil content was not correlated with yield or the other traits. The study revealed that treatment by trait (TT) biplot can graphically display the interrelationships among traits and facilitate visual comparison of treatments.
Vertical Profile and Temporal Variation of Chlorophyll in Maize Canopy: Quantitative “Crop Vigor” Indicator by Means of Reflectance‐Based Techniques
Authors: Ciganda Verónica , Gitelson Anatoly , Schepers James
Published: September 2008

Chlorophyll (Chl) content is among the most important crop biophysical characteristics. Chlorophyll can be related to photosynthetic capacity, thus, productivity, developmental stage, and canopy stresses. The objective of this study was to quantify and characterize the temporal variation of Chl content in the vertical profile of maize (Zea mays L.) canopies by means of a reflectance‐based, nondestructive methodology. A recently developed technique that relates leaf reflectance with leaf pigment content has been used for accurate leaf Chl estimation. The technique employs reflectance in two spectral bands: in the red edge (720–730 nm) and in the near infrared (770–800 nm). More than 2000 maize leaves were measured for reflectance and total and green area during a growing season. A bell‐shaped curve showed a very good fit for the vertical distribution of Chl content regardless of crop growth stage. The parameters and coefficients of the bell‐shape function were found to be very useful to interpret temporal changes in the vertical profile of each variable. Comparisons among Chl, leaf area index (LAI) and green LAI showed that Chl content was more sensitive to changes in the physiological status of maize than other biophysical characteristics. The quantification of Chl content in canopy should be seen as a useful tool to complement the information on green LAI or LAI. Its applicability will help to improve the understanding of the crop ecophysiology, productivity, the radiation use efficiency and the interplant competition.
Early Incidence of Soybean Seedling Pathogens in Iowa
Authors: Murillo‐Williams Adriana , Pedersen Palle
Published: September 2008

Soybean [Glycine max (L.) Merr.] seed yield is often limited by root‐infecting pathogens. This study was conducted to determine the prevalence of three root‐infecting seedling pathogens in a fumigated vs. a nonfumigated soil, to determine if incidence is greater in cultivars that lack resistance to soybean cyst nematode (Heterodera glycines Ichinohe, SCN), and how incidence of these pathogens relates to yield. From 2004 through 2006, a 2 ha section of a field was fumigated each year with a mixture of 1,3 dichloropropene + chloropicrin on a Webster clay loam at Nevada (fine‐loamy, mixed, superactive, mesic Typic Endoaquolls), and on a Salix silty clay loam at Whiting (fine‐silty, mixed, superactive, mesic Typic Hapludolls), IA. Average incidence in the nonfumigated sites (determined by enzyme linked immunosorbent assay [ELISA] tests) was 86, 47, and 9% for Pythium spp., Rhizoctonia solani, Phytophthora sojae, respectively. Fumigation increased yield by 10%, reduced Pythium spp. incidence 27%, and no reductions in incidence of R. solani and P. sojae were detected. Incidence of Pythium spp. and P. sojae was less for cultivars with resistance to SCN. Negative correlations were found of yield with root health ratings (−0.43), SCN initial populations (−0.37), the presence of Pythium spp. (−0.28), and P. sojae (−0.15). Pythium spp. were more prevalent than R. solani and P. sojae in soybean seedlings in Iowa, and it was more related to yield than the other two pathogens. More research is needed to investigate the possibility of SCN‐susceptible cultivars being exposed to greater Pythium spp. and P. sojae damage which may influence yield.
A Historical Summary of Alabama's Old Rotation (circa 1896): The World's Oldest, Continuous Cotton Experiment
Authors: Mitchell Charles C. , Delaney Dennis P. , Balkcom Kipling S.
Published: September 2008

After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long‐term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long‐term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2‐yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] in a 3‐yr rotation produced little long‐term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in‐row subsoiling, high‐residue, conservation tillage, and genetically modified cultivars in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha−1 in 2006, 14.8 Mg corn grain ha−1 in 1999, 6.34 Mg wheat ha−1 in 2001, and 4.50 Mg soybean ha−1 in 2004.
Turn Left for Sustainable Growth
Authors: Stiglitz Joseph
Published: September 2008

Joseph Stiglitz argues that only the left has a comprehensive program that will permit and provide sustainable growth.
Growth and Inequality in Closed and Open Economies: The Role of the Product Cycle
Authors: Ranjan Priya
Published: September 2008

The product cycle literature suggests that new goods have a higher skill intensity in the early phase of production, which declines once the production process becomes standardized. Using this insight it is shown how an increase in the rate of neutral technological progress, which frees up resources tied in the production of existing goods, leads to increased production of skill intensive new goods and consequently an increase in wage inequality. When technological progress is exogenous, a decrease in skill endowment or trade liberalization with a skill scarce country increases wage inequality but leaves the composition of production between new and standardized goods unaltered. When the rate of technological progress depends on research effort, trade between a skill-abundant Northern economy and a skill-scarce Southern economy can raise wage inequality in both countries and increase productivity growth in the latter. North-North trade increases both wage inequality and productivity growth.
Uses and misuses of progress curve analysis in enzyme kinetics
Authors: Nikolova Natalia , Tenekedjiev Kiril , Kolev Krasimir
Published: September 2008

Progress curve analysis is a convenient tool for the characterization of enzyme action: a single reaction mixture provides multiple experimental measured points for continuously varying amounts of substrates and products with exactly the same enzyme and modulator concentrations. The determination of kinetic parameters from the progress curves, however, requires complex mathematical evaluation of the time-course data. Some freely available programs (e.g. FITSIM, DYNAFIT) are widely applied to fit kinetic parameters to user-defined enzymatic mechanisms, but users often overlook the stringent requirements of the analytic procedures for appropriate design of the input experiments. Flaws in the experimental setup result in unreliable parameters with consequent misinterpretation of the biological phenomenon under study. The present commentary suggests some helpful mathematical tools to improve the analytic procedure in order to diagnose major errors in concept and design of kinetic experiments.
The current analysis of the effect of hyperbaric oxygen therapy on the frostbitten tissue: Experimental study in rabbits
Authors: Uygur Fatih , Noyan Nurettin , Sever Celalettin , Gümüş Tuna
Published: September 2008

Many experimental studies have been performed and the mechanism of hyperbaric oxygen therapy on the frostbitten tissue has not been elucidated. In this study, we evaluated the effect of hyperbaric oxygen therapy on the frostbitten ears of rabbits in an experimental animal model by examining the concentrations of thromboxane A2 (as thromboxane B2-Tx B2) and of prostaglandin I2 (PG I2) (as 6-keto-prostaglandin F1α-PG F1α) in tissues, and by counting the numbers of inflammatory cells (neutrophils and mast cells-MC) Hyperbaric oxygen therapy (HBO) at 2.5 ATA for 90 minutes twice daily for fourteen days to rabbits, the ears of which were subjected to frostbite, decreased presence of inflammatory cells (mast cells −75%; neutrophils −40%) and increased prostaglandin I2 (PG I2) (as 6-Keto-PGF1α) in the involved skin. Thromboxane A2 (TxA2) (as Tx B2) was unaffected. Our results revealed that an inflammatory process was the underlying cause of frostbite injury and that hyperbaric oxygen therapy was active in pathological situations involving an inflammatory process in frostbite.
External cavity wavelength tunable semiconductor lasers - a review
Authors: Mroziewicz B.
Published: September 2008

External cavity tunable lasers have been around for many years and now constitute a large group of semiconductor lasers featuring very unique properties. The present review has been restricted to the systems based on the edge emitting diode lasers set-up in a hybrid configuration. The aim was to make the paper as concise as possible without sacrificing, however, most important details. We start with short description of the fundamentals essential for operation of the external cavity lasers to set the stage for explanation of their properties and some typical designs. Then, semiconductor optical amplifiers used in the external cavity lasers are highlighted more in detail as well as diffraction gratings and other types of wavelength-selective reflectors used to provide optical feedback in these lasers. This is followed by a survey of designs and properties of various external cavity lasers both with mobile bulk gratings and with fixed wavelength selective mirrors. The paper closes with description of some recent developments in the field to show prospects for further progress directed towards miniaturization and integration of the external cavity laser components used so far to set-up hybrid systems.
New material systems for third generation infrared photodetectors
Authors: Rogalski A.
Published: September 2008

Third-generation infrared (IR) systems are being developed nowadays. In the common understanding, these systems provide enhanced capabilities-like larger numbers of pixels, higher frame rates, and better thermal resolution as well as multicolour functionality and other on-chip functions. In this class of detectors, two main competitors, HgCdTe photodiodes and quantum-well photoconductors, have being developed.

Recently, two new material systems have been emerged as the candidates for third generation IR detectors, type II InAs/GaInSb strain layer superlattices (SLSs) and quantum dot IR photodetectors (QDIPs).

In the paper, issue associated with the development and exploitation of multispectral photodetectors from these new materials is discussed. Discussions is focused on most recently on-going detector technology efforts in fabrication both photodetectors and focal plane arrays (FPAs). The challenges facing multicolour devices concerning complicated device structures, multilayer material growth, and device fabrication are described.
Corrugated SNOM probe with enhanced energy throughput
Authors: Antosiewicz T. , Szoplik T.
Published: September 2008

In a previous paper we proposed a modification of metal-coated tapered-fibre aperture probes for scanning near-field optical microscopes (SNOMs). The modification consists in radial corrugations of the metal-dielectric interface oriented inward the core. Their purpose is to facilitate the excitation of surface plasmons, which increase the transport of energy beyond the cut-off diameter and radiate a quasi-dipolar field from the probe output rim. An increase in energy output allows for reduction of the apex diameter, which is the main factor determining the resolution of the microscope. In two-dimensional finite-difference time-domain (FDTD) simulations we analyse the performance of the new type of SNOM probe. We admit, however, that the two-dimensional approximation gives better results than expected from exact three-dimensional ones. Nevertheless, optimisation of enhanced energy throughput in corrugated probes should lead to at least twice better resolution with the same sensitivity of detectors available nowadays.
Electronic Warfare
Authors: Inkol Robert
Published: September 2008

Electronic warfare (EW) concerns the concepts, doctrine, and technology for maximizing the military value of the electromagnetic spectrum. This value is achieved in several ways: exploiting signals emitted by an opponent's systems, degrading the ability of an opponent to use his systems, and the application of techniques and procedures for preserving the ability of friendly forces to use their own systems effectively. This article gives a general overview of the concepts and technologies associated with EW.