bluuebunny/crossref_metadata_2025_split huggingface dataset:
Response of multiple seeded cocklebur and other cocklebur types to herbicide treatment
Authors: Abbas Hamed K , Johnson Bobbie J , Pantone Dan J , Wax Loyd M , Hine Ron , Shier W Thomas 
Published: February 2005

AbstractMultiple seeded cocklebur has been found in the last decade in Texas, and described as a biotype of Xanthium strumarium L with up to 25 seeds per bur instead of the usual two. The multiple seeded bur typically produces up to nine seedlings, causing concern that it may be harder to control than normal seeded common cocklebur. The efficacies of a series of fungal and conventional commercial herbicides have been compared in the greenhouse on seedlings of multiple seeded cocklebur from Texas (MSC‐TX) and normal common cockleburs from Texas (NCC‐TX), Arkansas (NCC‐AR), Illinois (NCC‐ILL) and two from Mississippi (NCC‐MS#1, NCC‐MS#2). Three measures of herbicidal activity (reductions in plant height and dry weight, and mortality) were used. The fungal herbicide Alternaria helianthi (Hansf) Tubaki & Nishihara at 1 × 105 conidia ml−1 + 2 g liter−1 Silwet L‐77 with an 8‐h dew period was an effective herbicide with all biotypes, as were the commercial chemical herbicides chlorimuron (14.8 g ha−1), imazaquin (29.6 g ha−1), sodium hydrogen methylarsonate (MSMA; 279.1 g ha−1) and imazethapyr (39.5 g ha−1). The membrane‐disrupting organic arsenical MSMA was effective with all biotypes, whereas commercial chemical herbicides which act by inhibiting branched‐chain amino acid synthesis (chlorimuron, imazaquin and imazethapyr) were less effective against normal seeded common cocklebur biotypes with short stature. These studies showed that multiple seeded cocklebur was at least as susceptible to the biological agent A helianthi and to the conventional commercial herbicides studied as were normal seeded cockleburs, suggesting that existing methods should be adequate to control this novel biotype. Copyright © 2005 Society of Chemical Industry
State of the art in multiaxial phenomenological failure criteria for wood members
Authors: Kasal Bo , Leichti Robert J 
Published: February 2005

AbstractWood structural members are frequently subjected to loads resulting in multiaxial stress. Failure criteria ordinarily used for isotropic materials do not apply to orthotropic and anisotropic materials and their use may result in incorrect stress state interpretation. This paper summarizes the current state of the art in applying phenomenological failure criteria to wood and wood‐based materials.
Fresh and hardened properties of self‐consolidating concrete
Authors: Bonen David , Shah Surendra P 
Published: February 2005

AbstractSelf‐consolidating concrete, (SCC) is a new technology and the market share of its products is rapidly growing because of the economic opportunities and improvements of the quality of the concrete and the working environment. In view of the potential number of ingredients, SCC is a complex system that is usually proportioned with one or more mineral admixtures and one or more chemical admixtures. A key factor for a successful formulation is a clear understanding of the role of the various constituents in the mix and their effects on the fresh and hardened properties.The fundamental rheological properties of SCC are based on low yield stress, moderate viscosity and retention of the kinetic energy of the flowable mix by reducing the volume fraction of coarse aggregate. These measures are necessary for imparting the requested fluidity, segregation resistance and prevention of interparticle collision and blocking. A low yield stress is attained by incorporation of adequate contents of superplasticizer. The flow characteristics are further modified by changing the aggregate volume fraction, coarse‐to‐fine aggregate volume, and the composition of the other ingredients. The viscosity is controlled by the contents of the free water, superplasticizer, and the volume fraction of the solids in the mix. The two strategies for maintaining a moderate viscosity are based on either incorporation of high amounts of powder; i.e. total content of cementitious materials (referred to as powder type SCC) or addition of viscosity modifier agents (referred to as VMA type SCC).By analogy to the Powers and Brownyard gel–space ratio, the compressive strength can be approximated by calculating the binder‐space ratio. One of the main challenges is to impart the required rheological properties that allow desired flow and filling ability characteristics whilst retaining dynamic and static stability. With this respect, the density of the matrix and maximum size of aggregate cannot be overlooked as, within the range of practical attainable viscosities that allow a free‐flow, their effects on the resistance to segregation are as high or even greater than that of the effect of viscosity. Attention is also drawn to the higher shrinkage values of SCC, especially the inherent higher shrinkage associated with the powder type SCC.
Interface bond between FRP sheets and concrete substrates: properties, numerical modeling and roles in member behaviour
Authors: Ueda Tamen , Dai Jianguo 
Published: February 2005

AbstractThe success of most of strengthening or retrofitting technologies for concrete structures by using external bonded FRP sheets depends highly on the interface bond between the FRP sheets and concrete substrates. This paper reviews current studies on evaluating the bond properties of FRP sheet–concrete interfaces and, in particular, focuses on several newly developed bond models for describing the bond characteristics of FRP sheet–concrete interfaces under various loading conditions. This paper also gives several examples that apply these interfacial bond models to the design of different retrofitting cases. Analytical solutions are discussed that consider the local interfacial delamination and slip behaviour, which can improve the prediction of strength and deformation performances, as well as clarify the failure mechanisms of concrete members upgraded with FRP composites. Moreover, the improvement in structural performance of retrofitted concrete members is discussed by relating them to the optimum microscopic properties of the interface bond and the properties of retrofitting materials.
Local elastic response of individual grains in lead‐free Nb‐doped Bi4Ti3O12 piezoelectric ceramics
Authors: Zeng H. R. , Yu H. F. , Zhang L. N. , Chu R. Q. , Li G. R. , Yin Q. R. 
Published: February 2005

AbstractThe local elastic response of individual grains in lead‐free Nb‐doped Bi4Ti3O12 piezoelectric ceramics have been examined by atomic force microscopy in the acoustic mode. Subsurface features with different elasticity down to 60 nm are imaged from the cantilever deflection vibration at a modulation frequency much lower than the cantilever resonance. Local elastic regions parallel and perpendicular to the long axis of the plate‐like grains are found in the Bi4Ti3O12 piezoelectric ceramics, which are most likely a result of the crystal structure arrangement undergone in the grain growth of the Nb‐doped Bi4Ti3O12 piezoelectric ceramics during sintering. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of the toxicological joint effects between cyanogenic toxicants and aldehydes to Photobacterium phosphoreum
Authors: Lin Zhifen , Niu Xiaojun , Wu Chunde , Yin Kedong , Cai Zeping 
Published: February 2005

AbstractIn this study, a general approach is proposed that predicts the toxicological effects, to Photobacterium phosphoreum, of cyanogenic toxicants in combination with aldehydes. Forty binary mixtures containing an aldehyde and a cyanogenic toxicant were examined. The observed results indicate that the toxicological joint effects are different (additive, synergistic, or antagonistic) from each other, and the differences depend on chemical–chemical interactions between the cyanogenic toxicants and the aldehydes. Analysis of the chemical–chemical interactions reveals that there are two characteristics of individual chemicals that contribute to the joint effects: one is the charge of the carbon atom in the CHO group of aldehydes and the other is the charge of the carbon atom (C*) in the carbochain of cyanogenic toxicants. Based on these two contributors to toxicity, a quantitative structure‐activity relationship (QSAR) model can be derived, namely M=0.367−0.811σp−6.704 C* where r2=0.868, SE=0.232, F=121.769, P=0.000, M is the sum of toxic units; σp is the Hammett Constant and is used to evaluate the charge of the carbon atom in the CHO of aldehydes; C* is the charge of the carbon atom in the carbochain of cyanogenic toxicants. Application of this model to the eight other related mixtures demonstrates the consistency between the predicted and observed toxicities, with r2=0.888, SE=0.223, F=45.562 at P=0.000. This prediction capability convinces us that the QSAR model provides a general approach to prediction of the joint toxicological joint effects of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum.
The Better Predictive Model: High q2 for the Training Set or Low Root Mean Square Error of Prediction for the Test Set?
Authors: Aptula Aynur O. , Jeliazkova Nina G. , Schultz Terry W. , Cronin Mark T. D. 
Published: February 2005

AbstractThe process of validation of computational models (e.g., QSARs) may become the most important step in their development. Different requirements for the reliability and predictability of QSAR models have been described in the literature. Despite these formal recommendations there are few practical rules as to when to cease adding variables to a QSAR (i.e., what is an appropriate level of complexity of the model). In this work the influence of model complexity to statistical fit and error have been investigated using toxicity data for 200 phenols to the ciliated protozoan Tetrahymena pyriformis when applying a test set of a further 50 compounds. The results from this investigation showed that some important factors play a role in the definition of a good and reliable QSAR. These include the fact that q2 is not a good criterion for a model predictivity; that outliers should not necessarily be deleted as this may reduce the chemical space of the model; the number of descriptors in a multivariate model should be chosen carefully to avoid model under‐ and over‐estimation; and that an appropriate number of dimensions is required for PLS modelling.
QSAR Study of 2,3‐Benzodiazepin‐4(thi)one‐ and 1,2‐Phthalazine‐Related Negative Allosteric Modulators of the AMPA Receptor: A Structural Descriptors‐Based Reassessment
Authors: Buchwald Peter , Einstein Brandon , Bodor Nicholas 
Published: February 2005

AbstractIn an attempt to establish statistically more rigorous and chemically more meaningful quantitative structure‐activity relationship (QSAR) equations, a reassessment of a recent study of in vivo anticonvulsant activity for a set of 2,3‐benzodiazepin‐4(thi)one‐ and 1,2‐phthalazine‐related allosteric AMPA antagonists (n=61) is presented. Contrary to the original, relatively nonspecific descriptor set, which included, for example, a number of topological descriptors, specific structural descriptors that are much easier to interpret from a medicinal chemical point of view are used in this multiple linear regression‐based approach. Only statistically significant descriptors have been retained in the final equation, and whereas they give about the same correlation as those of the original paper on the training set (r2 of 0.79 vs. 0.76, n=49), they perform much better on the test set (predictive r$\rm{ {_{pr}^{2}}}$ of 0.73 vs. 0.05; r2 of 0.78 vs. 0.08, n=12). Descriptors found to be relevant are clearly related to substitutions at known pharmacophore positions, such as those corresponding to the 2,3‐, 7,8‐ and 4′‐positions of the benzodiazepine skeleton. Therefore, by a more careful selection of the descriptor set, both an improved prediction and a more intuitive quantitative interpretation could be achieved for this set of allosteric AMPA antagonists.
Investigations of taxoids by electrospray and atmospheric pressure chemical ionization with tandem mass spectrometry
Authors: Ye Min , Guo De‐an 
Published: February 2005

AbstractThe fragmentation behavior of taxoids was studied using electrospray (ESI) and atmospheric pressure chemical ionization (APCI) sources with multi‐stage tandem mass spectrometry. In the positive ion mode taxoids gave prominent [M+Na]+ and [M+K]+ ions with the ESI source, and [M+NH4]+ or [M+H]+ ions with the APCI source. The MS/MS fragmentations of ions produced by APCI and ESI sources were very similar. For both sources, the presence of cinnamoyl or benzoyl groups could be characterized by initial losses of 148 or 122 u, respectively, from molecular adduct ions. However, the elimination of cinnamic acid was relatively difficult for the molecular adduct ions formed by APCI, and was comparable in importance to the loss of acetic acid. The other fragments involved losses of CH2CO, CO, and H2O. The 5/7/6 type taxoids underwent characteristic losses of 58 or 118 u from ions produced by both APCI and ESI sources. The fragmentation behavior was remarkably influenced by substitution locations. The elimination of the C‐10 benzoyl group was usually the first fragmentation step, while that of the C‐2 benzoyl group was relatively difficult. The acetoxyl group at C‐7 was more active than those at C‐2, C‐9, and C‐10, which in turn were more active than that at C‐4. These fragmentation rules could facilitate the rapid screening and structural characterization of taxoids in plant extracts by high‐performance liquid chromatography/mass spectrometry (HPLC/MS). Copyright © 2005 John Wiley & Sons, Ltd.
On the stability of the organic dication of the bisquaternary ammonium salt decamethoxinum under liquid secondary ion mass spectrometry
Authors: Pashynska Vlada A. , Kosevich Marina V. , Gömöry Agnes , Szilágyi Zoltan , Vékey Karoly , Stepanian Stepan G. 
Published: February 2005

AbstractIn the course of a liquid secondary ion mass spectrometric (SIMS) investigation on a bisquaternary ammonium antimicrobial agent, decamethoxinum, unusual pathways of fragmentation of the organic dication M2+ of this bisquaternary salt, with preservation of the doubly charged state of the fragments, were observed. To reveal the structural and electronic parameters of decamethoxinum, which are responsible for the stabilization of its organic dication in the gas phase, a comprehensive SIMS study using metastable decay, collision‐induced dissociation and kinetic energy release techniques complemented by ab initio quantum chemical calculations was performed. Pathways of fragmentation of two main precursors originating from decamethoxinum—organic dication M2+ and its cluster with a Cl− counterion [M · Cl]+—and a number of their primary fragments were established and systematized. Differences in the pathways of fragmentation of M2+ and [M · Cl]+ were revealed: the main directions of [M · Cl]+ decay involve dequaternization similar to thermal degradation of this compound, while in M2+ fragmentation via loss of one and two terminal radicals with preservation of the doubly charged state of the fragments dominates over charge separation processes. It was shown that pairing of the dication with a Cl− anion does not preserve the complex from fragmentation via separation of two positively charged centers or neutralization (dequaternization) of one such center. At the same time the low abundance of M2+ in the SIMS spectra is to a larger extent controlled by a probability of M2+ association with an anion than by the decay of the dication per se.Quantum chemical calculations of the structural and electronic parameters of the decamethoxinum dication have revealed at least three features which can provide stabilization of the doubly charged state. Firstly, in the most energetically favorable stretch conformation the distance between the quaternary nitrogens (rN1‐N2 = 1.39 nm) is relatively large. Secondly, an intramolecular solvation of quaternary groups by carbonyl oxygens of the adjacent groups of the dication occurs, which contribute to structural stabilization. Thirdly, an important feature of the electronic structure of the dication is the presence of a partial negative charge on the nitrogen atoms and smearing of a positive charge mainly over the hydrogens of alkyl groups attached to the quaternary nitrogens, which reduces the net repulsion between the quaternary groups. The possible influence of charge smearing on the kinetic energy released on the dication fragmentation is discussed. Copyright © 2005 John Wiley & Sons, Ltd.
A high‐throughput liquid chromatography/tandem mass spectrometry method for screening glutathione conjugates using exact mass neutral loss acquisition
Authors: Castro‐Perez Jose , Plumb Robert , Liang Li , Yang Eric 
Published: February 2005

AbstractChemically reactive metabolites may cause hepatotoxicity and as a result liver failure or other adverse side reactions. Therefore, this is a vital topic of interest because early reactive metabolite screening may prevent compound failure at a later stage. In order to address this issue, a screening assay has been developed to detect the formation of reactive metabolites by using glutathione as a trapping reagent, which will allow us to search for phase I metabolites and also glutathiones during in vitro metabolite screening using liquid chromatography/tandem mass spectrometry (LC/MS/MS) with exact mass. Glutathione conjugations when fragmented by the mass spectrometer give a common loss corresponding to the pyroglutamic acid moiety, which can be monitored. Until recently, this work has been carried out with triple quadrupole technology using nominal mass. The advantage of the hybrid quadrupole time‐of‐flight mass spectrometer is the selectivity and sensitivity that can be achieved. Exact neutral loss detection is achieved via sequential low‐ and high‐energy MS acquisitions. After detection of the loss of the pyroglutamic acid moiety, using a window of ±20 mDa on the high‐energy scan, MS/MS is carried out on the parent mass of interest to confirm the common neutral loss. Copyright © 2005 John Wiley & Sons, Ltd.
A tandem mass spectrometric study of saccharides at high mass resolution
Authors: March Raymond E. , Stadey Christopher J. 
Published: February 2005

AbstractNine monosaccharides and four disaccharides were mass analyzed using a quadrupole time‐of‐flight tandem mass spectrometer combined with an electrospray ionization source. Product ion mass spectra of deprotonated, protonated, and sodiated saccharides were observed and were compared within each group of saccharides. Each of the deprotonated pentoses, hexoses and disaccharides yielded a significantly different product ion mass spectrum with the exception of α‐lactose and β‐lactose. The disaccharides α‐ and β‐lactose differ only at the glycosidic linkage. Product ion mass spectra of protonated and sodiated α‐ and β‐lactose were indistinguishable also. Copyright © 2005 John Wiley & Sons, Ltd.
Liquid chromatography/tandem mass spectrometry for pharmacokinetic studies of 20(R)‐ginsenoside Rg3 in dog
Authors: Li Ke , Chen Xiaoyan , Xu Jinghua , Li Xin , Zhong Dafang 
Published: February 2005

AbstractA sensitive and specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the investigation of the pharmacokinetics of 20(R)‐ginsenoside Rg3 in dog. The plasma samples were pretreated by liquid‐liquid extraction and analyzed using LC/MS/MS with an electrospray ionization interface. Dioscin was used as the internal standard. The method had a lower limit of quantitation of 0.5 ng/mL for Rg3 in 200 μL of plasma or 2 ng/mL in 100 μL of plasma, which offered a satisfactory sensitivity for the determination of Rg3 in plasma. The intra‐ and inter‐day precisions were measured to be below 8% and accuracy between −1.5 and 1.4% for all quality control samples. This quantitation method was successfully applied to pharmacokinetic studies of Rg3 after both an oral and an intravenous administration to beagle dogs. No Rh2 and protopanaxadiol were detected in plasma. Copyright © 2005 John Wiley & Sons, Ltd.
Interactions of dopamine D1 and D2 receptor antagonists with D‐methamphetamine‐induced hyperthermia and striatal dopamine and serotonin reductions
Authors: Broening Harry W. , Morford Laronda L. , Vorhees Charles V. 
Published: February 2005

AbstractThe effects of the dopamine D1 receptor antagonist R(+)‐SCH‐23390 and D2 receptor antagonist S(–)‐eticlopride on d‐methamphetamine‐induced striatal monoamine reductions 72 h after treatment were investigated in relation to changes in body temperature. Rats were administered four 10‐mg/kg doses of d‐methamphetamine or saline with a 2‐h interval between treatments; 0.5 mg/kg eticlopride or SCH‐23390 was administered 15 min before each methamphetamine or saline injection. Two ambient temperature conditions were investigated: 24 and 33°C. Methamphetamine administered at 24°C induced hyperthermia and reduced striatal dopamine content by 73%; 0.5 mg/kg eticlopride or SCH‐23390 administered in combination with methamphetamine at 24°C attenuated methamphetamine‐induced hyperthermia and prevented significant reductions in dopamine content. At 33°C, eticlopride and SCH‐23390 were ineffective in blocking methamphetamine‐induced hyperthermia and dopamine content was reduced by 65% in the SCH‐23390‐methamphetamine group. By contrast, dopamine content was reduced by only 31% in the 33°C eticlopride‐methamphetamine group. Thus, although the eticlopride‐methamphetamine treatment combination at 33°C exhibited a hyperthermic response comparable to that seen with methamphetamine alone at 24°C, reductions in dopamine content were attenuated in the combination group compared with methamphetamine alone at 24°C. Serotonin changes showed similar attenuated reductions after SCH‐23390 or eticlopride pretreatment at 24°C in combination with methamphetamine, but this attenuation was absent at 33°C. The dissociation of methamphetamine‐induced striatal dopamine reduction and hyperthermia seen after eticlopride pretreatment suggests a dopamine D2 receptor mechanism in mediating methamphetamine‐induced dopamine depletion. However this D2 mechanism does not apply to methamphetamine‐induced striatal serotonin reductions. Synapse 56:84–93, 2005. © 2005 Wiley‐Liss, Inc.