bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental observations on the seismic shear performance of RC beam‐to‐column connections subjected to varying axial column force
Authors: Agbabian M. S. , Higazy E. M. , Abdel‐Ghaffar A. M. , Elnashai A. S.
Published: April 2007

The paper presents results from the first series of an ongoing experimental study aimed at quantifying the effect of axial column load on the shear capacity of beam‐to‐column connections. This is deemed important due to the recent evidence showing that vertical earthquake ground motion, when combined with high overturning moments, may cause reduced column compression or even tension. In which case, the concrete contribution to shear resistance in the panel zone is diminished, which may lead to failure prior to the attainment of the full resisting capacity of the beam section. The results first show that the failure mode of the models was, as intended, shear failure of the panel zone. It is further observed that the axial column load has a marked effect on the shear deformation capacity, yield point, cracking pattern, ultimate capacity and ductility of the panel zone. Differences in the range of 30 per cent in capacity and 50 per cent in deformability were recorded. The preliminary results are useful in providing design guidance for structures located in areas of potential high vertical ground motion component. Also, for high‐rise structures, where there are large overturning moments, the results may be of use in ensuring a uniform safety factor (or overstrength) in various non‐dissipative parts of the structure.
Using accidental eccentricity in code‐specified static and dynamic analyses of buildings
Authors: de la Llera Juan Carlos , Chopra Anil K.
Published: April 2007

The differences between the increase in building response due to accidental eccentricity predicted by code‐specified static and dynamic analyses are studied for symmetric and unsymmetric single and multistorey buildings. The increase in response computed from static analysis of the building is obtained by applying the equivalent static forces at distance ea, equal to the storey accidental eccentricity, from the centre of mass at each floor. Alternatively, this increase in response is computed by dynamic analysis of the building with the centre of mass of each floor shifted through a distance ea from its nominal position. A parametric study is performed on single‐storey systems in order to evaluate the differences in response predicted by both analysis procedures. It is shown that these results are essentially the same as the ones obtained for a special class of multistorey systems. Upper and lower bounds for the differences in response computed from static and dynamic analyses are obtained for general multistorey systems. These differences in response depend primarily on the ratio of the fundamental torsional and lateral frequencies of the building. They are larger for small values of the frequency ratio and decrease to zero as the frequency ratio becomes large. Further, these discrepancies are in many cases of the same order as the code‐intended increase in response due to accidental eccentricity. This implies that the code‐specified static and dynamic analyses to account for accidental torsion should be modified to be mutually consistent.
Subgrade model for transient response analysis of multiple embedded bodies
Authors: Konagai Kazuo , Nogami Toyoaki
Published: April 2007

During the dynamic response of multiple partially or fully embedded structures, the subgrade medium at the sides of the structures not only generates the soil‐structure interaction forces but also transmits the motions from one structural body to others. With Winkler's hypothesis, these forces and motions are formulated in the time‐domain in a simple form utilizing the frequency‐domains formulations. The validity of the developed formulations is examined using small‐scale‐model test results obtained for piles in a synthetic ground. A numerical example is provided to demonstrate the approach proposed and the formulations developed. The simplified time‐domain formulations are found to be numerically efficient and yet capable of predicting the behaviour reasonably well.
Earthquake collapse analysis of steel frames
Authors: Challa V. R. Murty , Hall John F.
Published: April 2007

The non‐linear response of planar moment‐resistant steel frames is investigated with regard to P‐Δ‐type collapses under severe earthquake ground motions. The frame model employs configuration updating, fibre‐type beam‐column members with geometric stiffness, panel zone elements at the beam‐to‐column junctions, and realistic hysteretic relations which are used for both the fibres and panel zones. Frame design follows the 1991 Uniform Building Code, and three panel zone designs are considered. It is found that P‐Δ collapse of the 20‐storey frame examined results from the formation of a collapse mechanism involving the lowest few stories. Column hinging occurs even though the code requirement that column strength exceed beam strength is satisfied. Among the different panel zone designs, the weakest one proved most resistant to developing a collapse mechanism in the frame.
Dynamic response of single piles embedded in transversely isotropic layered media
Authors: Liu Weiming , Novak Milos
Published: April 2007

Dynamic response of single piles embedded in transversely isotropic layered media is investigated using the finite element method combined with dynamic stiffness matrices of the soil derived from Green's functions for ring loads. The influence of soil anisotropy on the dynamic behaviour of piles is examined through a series of parametric studies.
Dam‐foundation rock interaction effects in frequency‐response functions of arch dams
Authors: Tan Hanchen , Chopra Anil K.
Published: April 2007

The linear response of a selected arch dam to harmonic upstream, vertical or cross‐stream ground motion is presented for a wide range of the important system parameters characterizing the properties of the dam, foundation rock, impounded water and reservoir boundary materials. Based on these frequency‐response functions, the dam‐foundation rock interaction effects in the dynamic response of arch dams are investigated.
Dynamic response of a pair of walls retaining a viscoelastic solid
Authors: Veletsos A. S. , Parikh V. H. , Younan A. H.
Published: April 2007

Making use of a previously reported, simple, approximate method of analysis, a critical evaluation is made of the dynamic pressures and forces induced by horizontal ground shaking on a pair of infinitely long, parallel walls retaining a uniform viscoelastic solid. The walls are presumed to be rigid but elastically constrained against rotation at their base. The effects of both harmonic and earthquake‐induced excitations are examined. The accuracy of the method is assessed by comparing its predictions for the special case of fixed‐based walls with those obtained by an exact method, and comprehensive numerical data are presented which elucidate the underlying response mechanisms, and the effects and relative importance of the parameters involved. The parameters examined include the characteristics of the ground motion, the ratio of the distance between walls to the height of the contained material, and the flexibility of the rotational wall constraints. In addition to valuable insights into the responses of the systems investigated, the results presented provide a convenient framework for the analysis of more complex systems as well.
Displacement‐based design of RC bridge columns in seismic regions
Authors: Kowalsky Mervyn J. , Priestley M. J. Nigel , MacRae Gregory A.
Published: April 2007

This paper presents a seismic design philosophy based on displacements rather than forces. By inverting the seismic design process, a rational method is established where member strength and stiffness depend on the target displacement. A comprehensive procedure for displacement‐based design of cantilever bridge columns is presented and verified by dynamic inelastic time history analysis. Parameter studies are used to examine the influence of several variables within the possible design solution space.
Time domain procedure of FE‐BE‐IBE coupling for seismic interaction of arch dams and canyons
Authors: Chuhan Zhang , Feng Jin , Pekau O. A.
Published: April 2007

A procedure for three‐dimensional (3‐D) coupling of finite elements (FEs), boundary elements (BEs) and infinite boundary elements (IBEs) is presented for the numerical modelling of seismic interaction between arch dams and rock canyons. First, a system of coupling 3‐D boundary and infinite boundary elements is developed for simulation of infinite and irregular canyons and for determination, in the frequency domain, of impedance functions on the dam‐canyon interface. Secondly, the impedance functions for all degrees‐of‐freedom are transformed approximately into frequency independent discrete parameters by a curve fitting technique. Finally, these discrete parameters are combined with the dam structure which is discretized by finite elements, thus allowing the response of the arch dam‐canyon system to be evaluated. The proposed procedure is efficient because it permits the seismic analysis of arch dam‐canyon interaction by the substructure technique in the time domain. To demonstrate both the validity and efficiency of the present procedure, the response of an arch dam‐canyon system is obtained under unit impulse acting on the dam‐canyon interface as the free field input. Very good agreement is noted when comparing the frequency response determined from the time domain with that from the frequency domain under harmonic excitation applied on the interface of the dam‐canyon.
Volatile components of Thymus vulgaris L. from wild‐growing and cultivated plants in Jordan
Authors: Hudaib M. , Aburjai T.
Published: April 2007

The composition of the essential oil hydrodistilled from the aerial parts of Thymus vulgaris L. grown in Jordan has been determined by GC and GC–MS. Variations in oil composition and yield between cultivated and wild‐growing plants collected from different localities, at different altitudes, have been also evaluated. Higher oil yields were observed in plants growing wild (3.7–5.6% of dried material) than in cultivated plants (1.1–2.0%), and those collected from the Mshaqar region, in the middle of Jordan and at the highest altitude, were the richest in oil (∼5.4%). Generally, the oil was characterized by marked levels of phenolic monoterpenoids (mainly thymol and carvacrol) in the range 70.8–89.0%. High levels of the monoterpenoid hydrocarbons p‐cymene (3.4–8.2%) and γ‐terpinene (1.6–7.7%) were also observed. Other major components were 1,8‐cineole (up to 2.1%), α‐thujone (up to 1.2%), camphor (up to 1.1%) and β‐caryophyllene (0.2–2.8%). With the exception of plants growing wild in the Ramtha region, in the far north of Jordan, carvacrol was found as the principal phenol of all other oils (50.6–86.1%) and was dominant (>85%) in wild plant oils. The oil from Ramtha was characterized by the highest level of thymol (∼63.8%) as the dominant phenol and was most abundant in p‐cymene (8.2%), 1,8‐cineole (2.1%) and γ‐terpinene (7.7%). In addition to assigning carvacrol or thymol chemotypes to the plant, the high content of active monoterpenoid phenols strongly suggests a potential use of Jordanian thyme oil in cough products and antimicrobial–herbal drug combinations. Copyright © 2007 John Wiley & Sons, Ltd.
Changes in body mass, energy balance, physical function, and inflammatory state in patients with locally advanced head and neck cancer treated with concurrent chemoradiation after low‐dose induction chemotherapy
Authors: Silver Heidi J. , Dietrich Mary S. , Murphy Barbara A.
Published: April 2007

Background:

We aimed to determine changes in body mass and body composition in relation to energy balance, inflammatory state, and physical function before and after concurrent chemoradiation (CCR).

Methods:

Seventeen patients with stage III and IVa head and neck cancer, aged 58.9 ± 5.4 years, who had completed a 9‐week regimen of low‐dose induction chemotherapy came to the General Clinical Research Center pre‐ and post‐CCR for measurement of body mass composition by dual‐energy X‐ray absorptiometry, resting energy expenditure (REE) by indirect calorimetry, physical performance (by Modified Baecke Questionnaire and Reuben's Physical Performance Test), and functionality (Activities and Instrumental Activities of Daily Living scores). Fasting venous samples were collected to determine C‐reactive protein and cytokines interleukin (IL)‐1β, IL‐6, IL‐8, and IL‐10. Random 24‐hour telephone diet recalls assessed energy intakes.

Results:

Weight loss began 1 week after CCR. Lean body mass (LBM) accounted for 71.7% ± 21% of body mass loss. No change occurred in energy intakes or calorie/nitrogen ratio. REE was significantly increased when adjusted for LBM loss (kcal/kg), p = .019. LBM loss was significantly associated with physical performance decline, r = .71, p = .004, and increased functional dependence, r = .58, p = .02. Total physical activity level declined significantly, p = .003. Cytokine levels were strongly associated with physical and functional decline.

Conclusions:

The aberrant changes in body composition, metabolism, and inflammatory state were associated with clinically and statistically significant impairments in physical performance and function. Future investigations and clinical practice should combine nutrition with antiinflammatory agents and exercise activities to support lean tissue anabolism and prevent physical and functional decline of patients with head and neck cancer undergoing CCR. © 2007 Wiley Periodicals, Inc. Head Neck, 2007
Role of activated nuclear factor‐κB in the pathogenesis and therapy of squamous cell carcinoma of the head and neck
Authors: Allen Clint T. , Ricker Justin L. , Chen Zhong , Van Waes Carter
Published: April 2007

Background:

Nuclear factor‐κB (NF‐κB), a transcription factor known to modulate expression of factors involved in inflammation, immunity, proliferation, and apoptosis, is constitutively activated and plays a role in pathogenesis and therapeutic resistance in head and neck squamous cell carcinoma (HNSCC). Understanding the molecular alterations leading to aberrant NF‐κB activation in HNSCC may direct investigators to novel therapeutic targets.

Methods:

Results of laboratory and clinical studies are reviewed.

Results:

The structure, function, and activation of NF‐κB, products of NF‐κB target genes and their role in HNSCC oncogenesis, and current NF‐κB modulating interventions are described.

Conclusions:

Aberrant NF‐κB activation contributes to the expression of oncogenes and the malignant phenotype observed in HNSCC. NF‐κB, along with providing a link between cancer and inflammation, may serve as an appropriate therapeutic target to inhibit tumor growth and sensitize cancer cells to established cytotoxic anticancer therapies. © 2007 Wiley Periodicals, Inc. Head Neck, 2007
The training effects of principle knowledge on fault diagnosis performance
Authors: Ham Dong‐Han , Yoon Wan Chul
Published: April 2007

In regard to the effectiveness of types of knowledge on fault diagnosis performance, many experimental studies showed that training with procedural knowledge (diagnostic rules) is very effective to enhance diagnosis performance. But the effects of training with principle knowledge (theoretical knowledge) have been controversial. Some studies went so far as to claim that principle knowledge is not useful for diagnosis. However, common experience suggests that understanding the principles of system dynamics is valuable in certain diagnostic situations. In this study, we conducted an experiment to investigate the value of principle knowledge in various fault situations. A context‐free digital logic circuit including 41 gates of three basic types was simulated for the subjects to diagnose. The experimental results showed that instructing principle knowledge has positive effects that are dependent on the complexity of diagnostic problems. The observations also provide insights on how fault diagnosis benefits from principle knowledge. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 263–282, 2007.
Hippocampal size positively correlates with verbal IQ in male children
Authors: Schumann Cynthia Mills , Hamstra Julia , Goodlin‐Jones Beth L. , Kwon Hower , Reiss Allan L. , Amaral David G.
Published: April 2007

Historically, there have been numerous proposals that the size of the brain correlates with its capacity to process information. Little is known, however, about which specific brain regions contribute to this correlation in children and adolescents. This study evaluated the relationship between intelligence and the size of various brain structures in typically developing male children 8–18 yrs of age. Magnetic resonance imaging (MRI) scans were used to measure the volume of the cerebrum, cerebral gray and white matter, cerebellum, amygdala, and hippocampus. Gray matter and hippocampal volume significantly correlated with full scale and verbal IQ. Since the hippocampus strongly correlated with verbal but not performance IQ, our findings reinforce the hypothesis that the hippocampus is involved in declarative and semantic learning, which contributes more notably to verbal IQ, than to performance IQ. Given the substantial evidence for environmentally induced changes in hippocampal structure, an unresolved issue is whether this relationship reflects genetically determined individual variation or learning induced plasticity. © 2007 Wiley‐Liss, Inc.
Most human Alu and Murine B1 repeats are unique
Authors: Umylny Boris , Presting Gernot , Efird Jimmy T. , Klimovitsky Boris I. , Ward W. Steven
Published: April 2007

Alus and B1s are short interspersed repeat elements (SINEs) indirectly derived from the 7SL RNA gene. While most researchers recognize that there exists extensive variability between individual elements, the extent of this variability has never been systematically tested. We examined all Alu elements over 200 nucleotides and all B1 elements over 100 nucleotides in the human and mouse genomes, and analyzed the number of copies of each element at various stringencies from 22 nucleotides to full length. Over 98% of 923,277 Alus and 365,377 B1s examined were unique when queried at full length. When the criterion was reduced to half the length of the repeat, 97% of the Alus and 73% of the B1s were still found to be a single copy. All single and multi‐copy sequences have been mapped and documented. Access to the data is possible using the AluPlus website http://www.ibr.hawaii.edu. J. Cell. Biochem. 102: 110–121, 2007. © 2007 Wiley‐Liss, Inc.
Regulation of matrix Gla protein by parathyroid hormone in MC3T3‐E1 osteoblast‐like cells involves protein kinase A and extracellular signal‐regulated kinase pathways
Authors: Suttamanatwong Supaporn , Franceschi Renny T. , Carlson Ann E. , Gopalakrishnan Rajaram
Published: April 2007

Inhibition of osteoblast‐mediated mineralization is one of the major catabolic effects of parathyroid hormone (PTH) on bone. Previously, we showed that PTH induces matrix γ‐carboxyglutamic acid (Gla) protein (MGP) expression and established that this induction is critical for PTH‐mediated inhibition of osteoblast mineralization. In the present study, we focus on the mechanism through which PTH regulates MGP expression in osteoblastic MC3T3‐E1 cells. Following transient transfection of these cells with a −748 bp murine MGP promoter‐luciferase construct (pMGP‐luc), PTH (10 −7 M) induced promoter activity in a time‐dependent manner with a maximal four‐ to six fold induction seen 6 h after PTH treatment. Both H‐89 (PKA inhibitor) and U0126 (MEK inhibitor), suppressed PTH induction of MGP promoter activity as well as the MGP mRNA level. In addition, forskolin (PKA activator) stimulated MGP promoter activity and mRNA levels confirming that PKA is one of the signaling molecules required for regulation of MGP by PTH. Co‐transfection of MC3T3‐E1 cells with pMGP‐luc and MEK(SP), a plasmid encoding the constitutively active form of MEK, led to a dose‐dependent increase in MGP promoter activity. Both MGP promoter activity and MGP mRNA level were not affected by the protein kinase C (PKC) inhibitor, GF109203X. However, phorbol 12‐myristate 13‐acetate (PMA), a selective PKC activator induced MGP mRNA expression through activation of extracellular signal‐regulated kinase (ERK). Taken together, these results indicate that PTH regulates MGP via both PKA‐ and ERK‐dependent pathways. J. Cell. Biochem. 102: 496–505, 2007. © 2007 Wiley‐Liss, Inc.
Joint neighbors approximation of macromolecular solvent accessible surface area
Authors: Rychkov Georgy , Petukhov Michael
Published: April 2007

A new method for approximate analytical calculations of solvent accessible surface area (SASA) for arbitrary molecules and their gradients with respect to their atomic coordinates was developed. This method is based on the recursive procedure of pairwise joining of neighboring atoms. Unlike other available methods of approximate SASA calculations, the method has no empirical parameters, and therefore can be used with comparable accuracy in calculations of SASA in folded and unfolded conformations of macromolecules of any chemical nature. As shown by tests with globular proteins in folded conformations, average errors in absolute atomic surface area is around 1 Å2, while for unfolded protein conformations it varies from 1.65 to 1.87 Å2. Computational times of the method are comparable with those by GETAREA, one of the fastest exact analytical methods available today. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Scaleable purification process for gene therapy retroviral vectors
Authors: Rodrigues Teresa , Carvalho Andreia , Carmo Marlene , Carrondo Manuel J. T. , Alves Paula M. , Cruz Pedro E.
Published: April 2007

Background

Retroviral vectors (RVs) constitute one of the preferred gene therapy tools against inherited and acquired diseases. Development of scaleable downstream processes allowing purification under mild conditions and yielding viral preparations with high titer, potency and purity is critical for the success of clinical trials and subsequent clinical use of this technology.

Methods

A purification process for murine leukaemia virus (MLV)‐derived vector supernatants was developed based on membrane separation and anion‐exchange chromatography (AEXc). Initial clarification of the vector stocks was performed using 0.45 µm membranes followed by concentration with 500 kDa molecular weight cut‐off (MWCO) membranes; further purification was performed by AEXc using a tentacle matrix bearing DEAE functional ligands. Finally, concentration/diafiltration was performed by 500 kDa MWCO membranes. To validate final product quality the process was scaled up 16‐fold.

Results

Optimization of microfiltration membrane pore size and ultrafiltration transmembrane pressure allowed the recovery of nearly 100% infectious particles. Further purification of the RVs by AEXc resulted in high removal of protein contaminants while maintaining high recoveries of infectious vectors (77 ± 11%). Up‐scaling of the process resulted in high titer vector preparations, 3.2 × 108 infectious particles (IP)/ml (85‐fold concentration), with an overall recovery reaching 26%. The process yielded vectors with transduction efficiencies higher than the starting material and more than 99% pure, relative to protein contamination.

Conclusions

The combination of membrane separation and AEXc processes results in a feasible and scaleable purification strategy for MLV‐derived vectors, allowing the removal of inhibitory contaminants thus yielding pure vectors with increased transduction efficiencies. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of antimicrobial histone sequences and posttranslational modifications by mass spectrometry
Authors: Ouvry‐Patat Séverine A. , Schey Kevin L.
Published: April 2007

Histones typically play a role in DNA packaging and transcription regulation. These proteins are heavily modified by acetylation, methylation, phosphorylation and/or ubiquitination, and various combinations of these modifications alter histone functions and form the basis of the histone code. Furthermore, histones, including those found in shrimp, have recently been found to possess antimicrobial properties; however, the sequences and posttranslational modifications of shrimp histones are largely unknown. In this study mass spectrometry was used to characterize the primary structure of the shrimp antimicrobial histone. A combination of in‐solution digestion and in‐gel propionylation/digestion followed by LC‐MS‐MS and MALDI‐TOF‐TOF analysis was used. Over 80% of each histone sequence was obtained by in‐solution digestion; however, none of the N‐terminal domains was sequenced with this method. An in‐gel propionylation method was optimized to recover and sequence the extremely hydrophilic histone N‐termini. This method was then applied to shrimp hemocyte lysates separated on a 1‐D SDS‐PAGE gel. Overall, 95% coverage was obtained for the histone sequences as well as the identification of posttranslational sites such as acetylation, methylation and phosphorylation. Copyright © 2007 John Wiley & Sons, Ltd.
Exfoliation corrosion and electrochemical impedance spectroscopy of an Al‐Li alloy in EXCO solution
Authors: Li J.F. , Zheng Z.Q. , Li S.C. , Ren W.D. , Chen W.J.
Published: April 2007

The exfoliation corrosion and electrochemical impedance spectroscopy (EIS) of an Al‐2.8%Cu‐1.5%Li‐0.3%Mg‐0.3%Zn‐0.3%Mn‐0.15%Zr alloy with various aging states in EXCO solution were investigated. The equilibrium precipitates at grain boundaries are anodic to the alloy base at their adjacent periphery. With prolonging aging time, the amount and the size of the equilibrium precipitates at grain boundaries are increased, resulting in an enhanced susceptibility to exfoliation corrosion. At the beginning of immersion in EXCO solution, the EIS plot of the alloys is composed of a capacitive arc in the high frequency range and an inductive loop in the low frequency range. As immersion time is increased, two capacitive arcs appear in the high‐mediate and mediate‐low frequency ranges respectively and the appearance time of two capacitive arcs could be an indication of the speed of localized corrosion development in EXCO solution. The longer appearance time of two capacitive arcs of the under‐aged alloy indicates its slower localized corrosion development.
High temperature corrosion of alloy Haynes 556 in carburizing/oxidizing environments
Authors: Allam I.M. , Gasem Z.M.
Published: April 2007

The iron based alloy Haynes 556 has been recently used in hydrocarbon and carbonaceous environments due to its excellent resistance to carburization. This alloy outperforms stainless steels and some of the best commercial carburization‐resistant nickel‐based alloys. This paper is concerned with the behavior of alloy Haynes 556 in high temperature carburizing environments containing trace amounts of oxygen. Thermal cyclic exposures were conducted in 2% and 10% CH4/H2 gas mixtures at 800, 900, 1000, and 1100°C for 10 cycles, 50 h each. Carbon activities, oxygen partial pressures, and stabilities of oxides and carbides were used to identify the role played by the reaction products in providing protection. Thermodynamic analyses, weight changes, and microstructural characterization were correlated with environmental parameters and alloy composition to elucidate the causes of its marked resistance to carburization. The results indicate protective character in both gas mixtures under all exposure conditions except the most aggressive, namely 1100°C in 10% CH4/H2 gas mixture. Below 1000°C, the formation of Cr, Al, and Si oxides along with Cr carbides provides the primary means of protection. Catastrophic failure at 1100°C was manifested by extensive fracture and crack development within the outer substrate surface in the 10% CH4/H2 gas mixture resulting in a dramatic increase in weight gain. This has been attributed to the increased carbon pick‐up, coupled with the loss of the protective outer scales.
Necessary optimality conditions for fractional action‐like integrals of variational calculus with Riemann–Liouville derivatives of order (α, β)
Authors: El‐Nabulsi Rami Ahmad , Torres Delfim F. M.
Published: April 2007

We derive Euler–Lagrange‐type equations for fractional action‐like integrals of the calculus of variations which depend on the Riemann–Liouville derivatives of order (α, β), α>0, β>0, recently introduced by Cresson. Some interesting consequences are obtained and discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Controlled release of 2‐heptanone using starch gel and polycaprolactone matrices and polymeric films
Authors: Glenn Gregory M. , Klamczynski Artur P. , Shey Justin , Chiou Bor‐Sen , Holtman Kevin M. , Wood Delilah F. , Ludvik Charles , Hoffman Gloria DeGrandi , Orts William J. , Imam Syed
Published: April 2007

Varroa jacobsoni is a parasitic mite that is threatening the honeybee industry in many parts of the world. 2‐Heptanone, a natural product made by honeybees at low concentrations, is effective at elevated concentrations in controlling mite populations in honeybee colonies, especially when released over a 42 day period. An extrusion process was used to encapsulate 14, 18, and 25% 2‐heptanone in a polycaprolactone (PCL) matrix. Less than 18% of the 2‐heptanone was encapsulated in the PCL matrix. The high vapor permeability of PCL to 2‐heptanone resulted in a high flux rate and limited the usefulness of PCL as an encapsulation matrix for controlled‐release devices. A starch gel containing three times its weight in 2‐heptanone was prepared from starch‐based microcellular foam (MCF). The gel had compressive, tensile, and flexural strength values in the range of 0.56 to 1.9 MPa. 2‐Heptanone quickly evaporated from non‐laminated gels. However, when the gel was laminated with different polymeric films, a wide range of flux rates was obtained. The T50 for gels laminated or coated with poly(vinyl alcohol) (PVAL, 99% hydrolyzed) and ethylene‐vinyl alcohol copolymer (EVAL) was 72 and 1030 days, respectively. The most promising film was a starch/glycerol film that released 50% of the 2‐heptanone (T50) in approximately 13 days. Copyright © 2007 John Wiley & Sons, Ltd.
Swelling characterization of novel ternary semi‐IPNs: acrylamide/1‐vinylimidazole/PEG hydrogels
Authors: Üzüm Ömer Barış , Karadağ Erdener
Published: April 2007

New ternary semi interpenetrating polymer networks (semi‐IPNs) systems containing acrylamide (AAm), 1‐vinylimidazole (VI) and poly (ethylene glycol) (PEG) have been prepared. AAm/VI hydrogels and semi‐IPN's, poly (AAm/VI/PEG) with 0.25, 0.50, 0.75 and 1.00 g of PEG (per 1.00 g AAm) were prepared by free radical solution polymerization in aqueous solution of AAm with VI as comonomer and a multifunctional crosslinker such as 1,4 butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of VI and PEG content in hydrogels were examined. AAm/VI and AAm/VI/PEG hydrogels showed large extents of swelling in aqueous media, the swelling being highly dependent on the chemical composition of the hydrogels. Percentage swelling ratio of AAm/VI hydrogels and AAm/VI/PEG hydrogels was shown as 650–4167%. The values of equilibrium water content (EWC) of the hydrogels are between 0.8990 and 0.9750. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non‐Fickian in character. Copyright © 2007 John Wiley & Sons, Ltd.
TLC‐Densitometric analysis of artemisinin for the rapid screening of high‐producing plantlets of Artemisia annua L.
Authors: Koobkokkruad Thongchai , Chochai Araya , Kerdmanee Chalermpol , De‐Eknamkul Wanchai
Published: April 2007

A simple TLC‐densitometric technique has been developed for the rapid and accurate analysis of artemisinin in a large number of Artemisia annua plantlets cultured in vitro. This new analytical method is based on the structural conversion of artemisinin on a silica gel layer by ammonia vapour to form 10‐azadesoxyartemisinin, a chromophore‐containing compound (λmax 320 nm) that can be detected by UV‐based TLC densitometry. The TLC system was evaluated quantitatively in terms of product stability, precision, accuracy and calibration. Good linearity was obtained in the range of 0.01–0.12 µg artemisinin. The technique appeared to be accurate and sensitive as compared with the complicated pre‐column reaction‐HPLC technique. Among 90 samples of A. annua plantlets, the artemisinin content in the leaves appeared to be highly variable, ranging from 0.02 to 0.67% w/w dry weight. These results demonstrate that densitometric TLC can be a cheap and simple technique for the accurate screening of high‐artemisinin‐producing plants. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of the essential oil from the roots of Eupatorium cannabinum subsp. corsicum (L.) by GC, GC‐MS and 13C‐NMR
Authors: Paolini Julien , Costa Jean , Bernardini Antoine‐François
Published: April 2007

Eupatorium cannabinum subsp. corsicum (L.) is an endemic subspecies from the island of Corsica. The essential oil from the roots of this aromatic plant has been studied by GC, GC‐MS and by 13C‐NMR. In contrast to the essential oil from the aerial parts, which is dominated by hydrocarbon compounds (76.9%) and particularly by sesquiterpene components (43.3%), the essential oil from the roots was characterized by a high content of oxygenated compounds (61.0%), particularly oxygenated monoterpenes (54.0%). In the root oil, 106 components were identified representing 96.1% of the total amount. This oil was dominated by the monoterpenes esters (33%), the major components of which were neryl isobutyrate (17.6%), thymyl methyl oxide (15.1%), δ‐2‐carene (14.5%) and β‐pinene (5.7%). Aromatic esters, nerol derivatives (esters and diesters) and a benzofuran were investigated by GC‐MS using different ionization modes including electron impact ionization, and positive‐ and negative‐chemical ionization. These components have not previously been reported in the essential oil of aerial parts of E. cannabinum from Corsica island. Copyright © 2007 John Wiley & Sons, Ltd.
Selective ultrasound‐assisted extractions of lipophilic constituents from Betula alleghaniensis and B. papyrifera wood at low temperatures
Authors: Lavoie J.‐M. , Stevanovic T.
Published: April 2007

Betula alleghaniensis and B. papyrifera are widely distributed in the province of Québec (Canada) and, since these trees are valuable exports for the local lumber industry, large amounts of their residual ligneous biomass are available for further exploitation. Betula species are well known for their significant concentrations of triterpenes, some of which were recently discovered to present promising bioactivity. The secondary transformation of birch biomass could therefore become important for many industries, particularly the pharmaceutical industry. In the present study, extracts from birch sawdust were obtained using an optimised ultrasound‐assisted extraction in which the careful choice of temperature permitted a selective extraction of the targeted triterpenes. Moreover, compared with the classical Soxhlet method, higher extraction yields were obtained in a shorter time. The lipophilic extracts obtained using dichloromethane as a solvent were analysed by GC‐MS and the major compounds identified as lupane‐type cyclic triterpenoids accompanied by the non‐cyclic triterpene squalene. Numerous aliphatic long‐chain fatty acids were also found in the extracts together with phytosterols. Betulonic acid and squalene, the major extract constituents for both B. alleghaniensis and B. papyrifera, are both bioactive molecules. Copyright © 2007 John Wiley & Sons, Ltd.
Poly(ethylene oxide)/clay nanocomposites for solid polymer electrolyte applications
Authors: Ratna Debdatta , Divekar Swapnil , Patchaiappan Sivaraman , Samui Asit Baran , Chakraborty Bikash Chandra
Published: April 2007

Poly(ethylene oxide) (PEO)/clay nanocomposites were prepared using a solution intercalation method. The organoclay (Nanocore I30E) used for nanocomposite synthesis was basically an octadecylammonium salt of montmorillonite clay prepared using an ion exchange method. Nanocomposite‐based solid polymer electrolytes were prepared using LiBF4. The nanocomposite structures were characterised using wide‐angle X‐ray diffraction. The crystallisation behaviour and thermal properties were studied using differential scanning calorimetry. It was found that the crystallinity of the composite electrolytes decreases with increasing clay concentration up to 7.5 wt% and then increases with a further increase in clay concentration. The trend is different from that observed in PEO/clay nanocomposites without lithium salt where the crystallinity gradually decreases with increasing clay concentration. The solid polymer electrolyte samples were evaluated using an alternating current impedance analyser. A considerable increase in room temperature conductivity was observed at the optimum clay concentration. The conductivity decreases beyond the optimum clay concentration. Copyright © 2007 Society of Chemical Industry
Effect of unsaturated chain end‐group on thermal oxidative behavior of polypropylene
Authors: Nakatani Hisayuki , Suzuki Shoutarou , Tanaka Takamasa , Terano Minoru
Published: April 2007

In order to clarify the influences of unsaturated chain end‐groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy (ΔE) for the oxidative degradation reactions of Ziegler‐catalyzed iPP (ZiPP) and metallocene‐catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature dependence of the oxidation induction time as determined by thermogravimetric analysis over the range 130–145 °C. The correlation between the content of unsaturated chain end‐groups and the change of ΔE was also studied. The results obtained indicated that the unsaturated chain end‐groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer‐like MiPP having unsaturated chain end‐groups, the ΔE value of ZiPP became lower, suggesting that iPP having unsaturated chain end‐groups served as an infectious agent of the degradation. Copyright © 2007 Society of Chemical Industry
Monodisperse polymeric spheres in the micron size range by a single step process
Authors: Almog Yaacov , Reich Shimon , Levy Moshe
Published: April 2007

A method for the formation of monodisperse polystyrene (PS) and polymethylmethacrylate (PMMA) spheres, in the micron diameter range, was developed. The polymerisation reaction was carried out in a series of alcohols, using homo‐ and co‐polymers as steric stabilisers in combination with a quaternary ammonium salt which probably acts as an electrostatic co‐stabiliser. Monodisperse PS spheres were formed in the particle size range of 1–6 μm, by a single step process. The size range could be extended by further addition of monomer to the reaction mixture during the polymerisation. The solubility parameter of the alcohol used and the nature of the surfactant determine the diameter of the resulting spheres. However, the concentration of surfactant did not seem to affect strongly the size of the spheres but only the dispersity.
Preparation and properties of phenolated phenanthrene‐formaldehyde resins
Authors: Herbert Lesley D. , Robinson J. Gordon , Marr George
Published: April 2007

Phenanthrene‐formaldehyde resins of different oxygen content were reacted with phenol 110°C in the presence of a strong acid catalyst. Cleavage occurred at the dimethylene ether and acetal bridges joining the aromatic nuclei with the concomitant formation of phenanthrene‐formaldehyde‐phenol resins. These resins were characterised by gel permeation chromatography, 1H n.m.r. and infrared spectroscopy.
Study of cure of epoxy resins by torsional braid analysis
Authors: Lee W. Alex , Oliver Martin J.
Published: April 2007

The use of torsional braid analysis (TBA) for the dynamic mechanical characterisation of polymers in composites has been inhibited to some degree by difficulties associated with both the measurement and processing of data. Methods for overcoming difficulties associated with spurious motions of the TBA pendulum and for the rapid and optimum processing of raw output data are outlined. A description follows of the application of the modified TBA technique to the analysis of six nominally similar epoxy resins systems. It is shown, by the presentation of comparative data, that the TBA method gives highly reproducible results, with little scatter, in studies both of gelation and vitrification times over a wide range of isothermal temperatures, and of activation energies for the processes involved, and also in studies of dynamic mechanical behaviour over a wide temperature range.
Chromatographic studies of epoxy resins
Authors: Hinton Ian G.
Published: April 2007

Methods are given for the‘derivatisation’ of various of the components of epoxy resins: after fractionation by g.p.c. but before further analysis by h.p.l.c. or g.p.c.

This paper describes the use of the following reagents for this purpose: concentrated HCl (to convert epoxy groups into chlorohydrin units); solid NaOH (to convert 1, 2‐chlorohydrin groups into epoxy units); phenol (to open epoxy rings); N‐methylaniline (to open epoxy rings); and KMnO4 (to oxidise —CH2 — and — OCH2CHOHCH2O — bridging units).
The examination of some thermosetting polymers by inelastic electron tunnelling spectroscopy
Authors: Comyn John , Horley Colin C. , Oxley David P. , Pritchard Robert G. , Tegg Janet L.
Published: April 2007

This paper first discusses the principles of Inelastic Electron Tunnelling Spectroscopy (IETS) and describes the experimental procedures needed to obtain spectra. Spectra are presented for an epoxide resin and two aliphatic amine‐hardeners, and for epoxideamine mixtures both before and after a heat curing schedule. From the latter it can be seen that the normal curing reaction between amine and epoxide groups does not take place within an IETS junction. A possible reason for this is the adsoprtion of amines onto the aluminium oxide surface of the substrate.
Addition of polyethersulphone to epoxy resins
Authors: Bucknall Clive B. , Partridge Ivana K.
Published: April 2007

Phase separation of polyethersulphone from solution in epoxy resins has been studied as a function of polyethersulphone concentration, type of resin, and curing conditions. The resins chosen were a rapidly curing tetrafunctional and a trifunctional epoxy resin, hardened with either diaminodiphenylsulphone, or dicyandiamide. Fracture surfaces of some of the cured blends exhibited nodular features between 0.2μm and 6μm in diameter. Using X‐ray microanalysis and scanning electron microscopy these nodules were shown to contain high concentrations of polyethersulphone. Mechanical properties, including fracture energy, dynamic mechanical relaxation and creep, were studied for the same range of blend compositions. Dynamic mechanical spectra provided further evidence for phase separation in certain blends, while elastic modulus, fracture toughness and creep showed little dependence upon composition.
Toughened multiphase thermosetting polymers
Authors: Kinloch A. J.
Published: April 2007

In recent years a new generation of advanced structural adhesives has become available. They are typically based upon epoxy resins modified by the presence of a second phase of dispersed rubbery particles. This multiphase microstructure results in the material possessing a considerably higher toughness or crack resistance, compared to the unmodified, single‐phase resin, but with only a minimal reduction in other important properties such as modulus and high‐temperature and creep resistance. Even more recently, polyimide adhesives have also been toughened employing this principle.

The present paper considers the following aspects:

The chemistry of rubbery‐toughened thermosetting polymers developed for adhesive applications.

Structure‐property relationships of multiphase adhesives which incorporate a dispersed rubbery phase or rigid particulate fillers. The mechanisms of toughening are discussed and related to the microstructure. The effects of volume fraction, particle size and particle size distribution on the polymer's fracture energy are also described

The particular problems encountered when using such toughened multiphase adhesives in structural joints are reviewed, including aspects of joint design and environmental effects.
Mechanistic aspects of polysaccharide complexation by quaternary ammonium salts, based on the reaction of Xanthan gum with [1‐14C]cetyltrimethylammonium bromide (Part II)
Authors: Kennedy John F. , Bradshaw Ian J. , Barker S. Alan
Published: April 2007

Complex formation between cetyltrimethylammonium bromide (CTAB) and xanthan gum in Xanthomonas campestris fermentation broth has been further used to exemplify the reaction between carboxy group — containing polysaccharides and quaternary ammonium salts. The variation of the molar ratio of xanthan gum: CTAB in the supernatant with variation of addition of quaternary ammonium salt is one parameter of the reaction which shows a definite relationship. Although this molar ratio in the supernatant is high (> 1) during the initial stages of the reaction, when little precipitation of the polysaccharide is occurring; it appears that the ratio must be below a critical value of about one before the end‐point of the complexation reaction can occur. The molar ratio of xanthan gum:CTA in the complex is initially exaggerated due to precipitation of polysaccharide with uncomplexed carboxy groups, but this ratio attains a constant value during the final stages of the reaction. A surprising observation of this study was the evidence obtained that CTAB added to X. campestris fermentation broth in excess of the complexation reaction end‐point requirement is associated with the insoluble xanthan gum‐CTA complex and is not present in the supernatant. Several possible explanations have been put forward to account for this observation. On the basis of this and another recent study, a detailed model of the mechanism of the complexation reaction between xanthan gum and CTAB in aqueous solution has been proposed. Discussion has been given to the implications and applicability of this particular complexation reaction mechanism.
The synthesis of the cyclolinear polyphosphazene
Authors: Kajiware M. , Kurachi Y.
Published: April 2007

The reaction of N,N‐diethylphosphoamidic dichloride and diaminotetraaryloxy‐cyclotriphosphazene in THF did not form a cyclolinear polyphosphazene. On the other hand, N,N‐diethylphosphoryltriamide with hexachloro‐cyclotriphosphazene in chloroform and triethylamine gave a product which was reacted with sodium phenoxide in THF solvent to give an amorphous solid, having a molecular weight distribution of 2,200–37,000. Proton n.m.r. indicated that nongeminal substitution had occurred. The product afforded non flammable films.
Direct determinations of the unperturbed dimensions of linear polyethylene molecules
Authors: Muraoka Yoichiro , Kamide Kenji , Suzuki Hidematsu
Published: April 2007

Light scattering measurements were carried out on three linear polyethylene samples in diphenyl at 127.5°C, i.e., under theta conditions. The unperturbed molecular dimensions and hence the characteristic ratio Cn were directly determined without recourse to theory for the excluded volume effect. It was found that the values of Cn were 8.7 to 10.5 in this theta solvent. These values suggest that the parameters, assigned to agree with the Cn value of 6.7, should be re‐examined for the refinement of theory.