bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of substitution degree of photoreactive groups on the properties of UV‐fabricated chitosan scaffold
Authors: Ling Kai , Zheng Fei , Li Junli , Tang Rupei , Huang Jin , Xu Yongmei , Zheng Hua , Chen Jinghua
Published: December 2007

Hydroxypropyl chitosan (HPCS), a water‐soluble chitosan derivate, was modified by introducing photoreactive azide groups (4‐azidobenzoic acid, Az‐) to the amino groups of HPCS, resulting in a photocrosslinkable Az‐HPCS. Novel porous chitosan scaffolds thus were fabricated by ultraviolet (UV) light irradiation of Az‐HPCS aqueous solutions. Fourier transform infrared spectroscopy, scanning electron microscopy, measurement of pore size and porosity, mechanical test, swelling test, in vitro biodegradation determination were used to analyze the effects of degree of substitution (DS) of Az‐groups on the properties of the scaffolds. When DS of Az‐groups increased from 2.8% to 5.6%, we found that (i) the pore size of Az‐HPCS scaffolds increased by about twofold and the porosity increased slightly, probably due to more N2 released from the crosslinking reaction with the increase of DS; (ii) both the tensile stress and strain increased by about threefold, relating to the increase of joint points, pore size, and porosity at a relative high DS; (iii) the swelling ratio and degradation rate decreased with the increase of Az‐DS, because of the forming of a more compact network structure. Preliminary data of cell culture on Az‐HPCS scaffold suggested its potential applicability for tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Liver tissue responses to gelatin and gelatin/chitosan gels
Authors: Wang Xiaohong , Yu Xin , Yan Yongnian , Zhang Renji
Published: December 2007

Gelatin and gelatin/chitosan gels, crosslinked using glutaraldehyde, were previously developed as substrates for three‐dimensional cell‐assembly techniques. In this study, the biocompatibility and biodegradation of gelatin and gelatin/chitosan gels were evaluated following implantation in rat livers for periods up to 16 weeks. The two gels were characterized by different inflammatory responses and degradation rates. The gelatin/chitosan gel is more efficient in inducing fibrin formation and vascularization at the implant‐host interface. The degrees of inflammatory reaction for the gelatin/chitosan gel were significantly stronger than the gelatin gel. Advanced biodegradation of the gelatin gels was observed. These data indicate that the gelatin gel has better liver tissue biocompatibility and a faster biodegraded rate than the gelatin/chitosan gel. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Shell–core imprinted polyacrylamide crosslinked chitosan for albumin removal from plasma
Authors: Okutucu Burcu , Zihnioglu Figen , Telefoncu Azmi
Published: December 2007

Molecularly imprinted polymeric beads were prepared using albumin as the imprinted molecule, acrylamide as the functional monomer, and epichlorhydrin crosslinked chitosan beads as the supporting matrix. The recognition and binding of the imprinted beads was also tested with human plasma for the targeted removal of HSA. Plasma is a rich source of biochemical products that can act as biomarkers of disease or physiological status of a patient. The application of current proteomic technologies in the search for potential diagnostic/prognostic indicators in the plasma of patients is limited by highly abundant albumin that constitute >60% of the total plasma proteins. Removal of abundant proteins will help in the discovery and detection of less abundant proteins that may prove to be informative. The adsorption capacities of the imprinted polymeric beads for pure human serum albumin and plasma albumin were estimated as 92% and 80%, respectively. The easy preparation protocol of derivatised beads and good protein recognition properties make them attractive for biotechnologic approaches. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Synthesis and characterization of collagen‐chitosan‐hydroxyapatite artificial bone matrix
Authors: Wang Yan , Zhang Lihai , Hu Min , Liu Hongchen , Wen Weisheng , Xiao Hongxi , Niu Yu
Published: December 2007

In this study, a new artificial bone matrix was constructed with collagen and Ca5(PO4)3OH (hydroxyapatite/HA) which are the main components of natural bone. To improve the property of the artificial bone matrix, chitosan (CS), a kind of positive charged polysaccharide, was crosslinked into the scaffolds. Solid–liquid phase separation method was used to shape 3D porous structure benefited for cells growing into. The artificial bone matrix was investigated by transmission electron microscopy, scanning electron microscopy, and electron spectroscopy for chemical analysis, etc. for structures and characteristics. And its ability of bone repair was investigated by orthotope bone defect reparation in vivo. The results showed that the artificial bone matrix was a porousscaffold with three‐dimension interconnected fiber microstructure. HA particles were dispersed evenly among collagen fiber and CS was modified on the surface of collagen fiber. It was indicated that this artificial bone matrix could be used as a bone substitute with outstanding properties. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Fibronectin and pellet suspension culture promote differentiation of human mesenchymal stem cells into insulin producing cells
Authors: Chang Ching‐Fang , Hsu Ke‐Hsun , Chiou Shih‐Hwa , Ho Larry Low‐Tone , Fu Yu‐Show , Hung Shih‐Chieh
Published: December 2007

Multipotential mesenchymal stem cells (MSCs) isolated from bone marrow can differentiate into multiple mesenchymal tissues and exhibit a neuronal phenotype under appropriate induction conditions. Methods promoting neural differentiation have been adapted to derive insulin producing cells (IPCs) from embryonic stem cells, but it remains unclear whether neuronal cell‐based differentiation method will be able to derive IPCs from MSCs. Using a four‐stage differentiation protocol which contains neuronal differentiation factor and IPC‐conversion reagent‐nicotinamide, the potential of human MSCs to differentiate into IPCs was evaluated by means of reverse transcription–polymerase chain reaction, immunostaining, and functional analysis. MSCs in monolayer spontaneously expressed genes for islet transcription factors, Nkx6.1 and Ngn3, but did not express insulin after treatment in this protocol. Pellet suspension culture and the addition of fibronectin enhanced pancreatic differentiation with increase in insulin and Glut2 gene expression. Switching of cells to high‐glucose culture further increased immunostaining for proinsulin and insulin. IPCs secreted insulin in response to elevated glucose concentration, which was regulated by reagents that increase cyclic AMP production or modify calcium influx. Our data suggest that MSCs in the monolayer do not undergo IPC differentiation and pellet suspension culture with fibronectin promotes IPCs derived from MSCs. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Successful management of a Jehovah's Witness with thrombotic thrombocytopenic purpura unwilling to be treated with therapeutic plasma exchange
Authors: Dabak Vrushali , Kuriakose Philip , Raman Sundara
Published: December 2007

Thrombotic thrombocytopenic purpura (TTP) is a life‐threatening disease treated successfully with plasma exchange. Jehovah's Witnesses whose religious beliefs preclude them from accepting plasma exchange may require alternative forms of therapy. We report a case of one such patient who presented with TTP, whom we successfully managed with vincristine and responded favorably without the need for plasma exchange. J. Clin. Apheresis, 2007. © 2007 Wiley‐Liss, Inc.
Distinct osteoblastic differentiation potential of murine fetal liver and bone marrow stroma‐derived mesenchymal stem cells
Authors: Fromigué Olivia , Hamidouche Zahia , Chateauvieux Sébastien , Charbord Pierre , Marie Pierre J.
Published: December 2007

Bone marrow‐derived mesenchymal stem cells (MSC) are able to differentiate into osteoblasts under appropriate induction. Although MSC‐derived osteoblasts are part of the hematopoietic niche, the nature of the stromal component in fetal liver remains elusive. Here, we determined the in vitro osteoblastic differentiation potential of murine clonal fetal liver‐derived cells (AFT024, BFC012, 2012) in comparison with bone marrow‐derived cell lines (BMC9, BMC10). Bone morphogenetic protein‐2 (BMP2) increased alkaline phosphatase (ALP) activity, an early osteoblastic marker, in AFT024 and 2012 cells, whereas dexamethasone had little or no effect. BMP2, but not dexamethasone, increased ALP activity in BMC9 cells, and both inducers increased ALP activity in BMC10 cells. BMP2 increased ALP mRNA in AFT024, 2012 and BMC9 cells. By contrast, ALP was not detected in BMC10 and BFC012 cells. BMP2 and dexamethasone increased osteopontin and osteocalcin mRNA expression in 2012 cells. Furthermore, bone marrow‐derived cells showed extensive matrix mineralization, whereas fetal liver‐derived cell lines showed no or very limited matrix mineralization capacity. These results indicate that the osteoblast differentiation potential differs in bone marrow and fetal liver‐derived cell lines, which may be due to a distinct developmental program or different microenvironment in the two hematopoietic sites. J. Cell. Biochem. 104: 620–628, 2008. © 2007 Wiley‐Liss, Inc.
Two modes of ERK activation by TNF in keratinocytes: Different cellular outcomes and bi‐directional modulation by vitamin D
Authors: Ziv Ester , Rotem Carmela , Miodovnik Mor , Ravid Amiram , Koren Ruth
Published: December 2007

Inflammation, elicited in the skin following tissue damage or pathogen invasion, may become chronic with deleterious consequences. Tumor necrosis factor (TNF) is a key mediator of cutaneous inflammation and the keratinocyte an important protagonist of skin immunity. Calcitriol, the hormonally active vitamin D metabolite, and its analogs attenuate epidermal inflammation and inhibit the hyperproliferation of keratinocytes associated with the inflammatory disorder, psoriasis. Since activation of extracellular signal‐regulated kinase (ERK) promotes keratinocyte proliferation and mediates epidermal inflammation, we studied the effect of calcitriol on ERK activation in HaCaT keratinocytes exposed to the ubiquitous inflammatory cytokine TNF. By using the EGF receptor (EGFR) tyrosine kinase inhibitor, AG1487 and the Src family inhibitor, PP‐1, we established that TNF activated ERK in an EGFR and Src dependent and an EGFR and Src independent modes. EGFR dependent activation resulted in the upregulation of the transcription factor, c‐Fos, while the EGFR independent activation mode was of a shorter duration, did not affect c‐Fos expression but induced IL‐8 mRNA expression. Pretreatment with calcitriol, enhanced TNF‐induced EGFR‐Src dependent ERK activation and tyrosine phosphorylation of the EGFR, but abolished the EGFR‐Src independent ERK activation. These effects were mirrored by enhancement of c‐Fos and inhibition of IL‐8 induction by TNF. Treatment with calcitriol increased the rate of the de‐phosphorylation of activated ERK, accounting for the inhibition of EGFR‐Src independent ERK activation by TNF. It is possible that effects on the ERK cascade contribute to the effects of calcitriol and its synthetic analogs on cutaneous inflammation and keratinocyte proliferation. J. Cell. Biochem. 104: 606–619, 2008. © 2007 Wiley‐Liss, Inc.
Prediction of the effects of imperfect construction of a QMS filter
Authors: Taylor Stephen , Gibson John R.
Published: December 2007

Modelling techniques have previously predicted the observed behaviour of perfectly manufactured QMS mass filters. These methods are extended to examination of the behaviour of imperfect QMS filters; this examination considers the behaviour of QMS filters with one rod displaced radially inward as this is a simple manufacturing defect that arises when a rod does not fit correctly into the mounting.

The results demonstrate the well known, but poorly documented property, that exchanging the connections of a poorly performing QMS device sometimes improves performance. This is shown to arise because only a displacement of a y‐rod produces a large effect. The results also show that displacement of a y‐rod may produce a spurious additional peak known as a precursor. More detailed investigation suggests that precursors are not separate peaks but are formed because a section of the main peak is removed causing an apparent double peak.

Finally results confirm that adjustment of the voltage applied to a displaced rod can be used to significantly improve the QMS behaviour. A small change by a fraction α in the position of a single rod may be compensated by a change of 2 × α in the voltage applied to that rod. Copyright © 2007 John Wiley & Sons, Ltd.
An efficient method for dephosphorylation of phosphopeptides by cerium oxide
Authors: Tan Feng , Zhang Yangjun , Wang Jinglan , Wei Junying , Cai Yun , Qian Xiaohong
Published: December 2007

In this article, an effective method for dephosphorylation of phosphopeptides by cerium oxide is described. The dephosphorylation activity of cerium oxide was evaluated by two standard phosphopeptides and the phosphopeptides in digests of phosphoprotein α‐casein and β‐casein. Results showed that the dephosphorylation of all the phosphopeptides was completed in 10 min, and temperature had little effect on the dephosphorylation, the dephosphorylation could be carried out at 0 °C, room temperature and 37 °C. The dephosphorylation mediated by cerium oxide can be attributed to Lewis acid and nucleophile activations. Advantages of using cerium oxide as catalyst for the dephosphorylation include: safe, simple, high catalytic activity, and no precise control of the treatment temperature. The method is valid for the phosphorylation of Ser, Thr and Tyr, and can be used for phosphoprotein analysis. Copyright © 2007 John Wiley & Sons, Ltd.
Neuroserpin regulates N‐cadherin‐mediated cell adhesion independently of its activity as an inhibitor of tissue plasminogen activator
Authors: Lee Tet Woo , Coates Leigh C. , Birch Nigel P.
Published: December 2007

Neuroserpin is an inhibitor of tissue plasminogen activator (tPA) that is expressed in developing and adult nervous systems. Spatial and temporal analysis of neuroserpin expression suggests that it is involved in regulating the proteolytic balance associated with axonogenesis and synaptogenesis during development and synaptic plasticity in the adult. Here we demonstrate that altered expression of neuroserpin modulates the degree of cell–cell adhesion in pheochromocytoma PC12 cells independently of its role as an inhibitor of tPA. Levels of the homophilic cell–cell adhesion molecule N‐cadherin are increased in neuroserpin‐overexpressing cell lines. N‐cadherin immunoreactivity was detected in a Triton X‐100‐insoluble fraction and localized to regions of cell contact, consistent with a role in enhancing cell surface adhesion. PC12 cell lines expressing neuroserpin mutants that lack tPA inhibitory activity also showed increased cell–cell adhesion and N‐cadherin expression. Our results identify neuroserpin as a novel regulator of cell–cell adhesion and the synaptic adhesion molecule N‐cadherin as a key effecter in this response. In nerve cells, neuroserpin may regulate the levels of N‐cadherin available for construction, maintenance, and control of synapses and synaptic dynamics. © 2007 Wiley‐Liss, Inc.
Screening of phenylalanine ammonia lyase in plant tissues, and retention of activity during dehydration
Authors: Goldson Andrea , Lam Melanie , Scaman Christine H , Clemens Sabine , Kermode Allison
Published: December 2007

BACKGROUND: Oral therapy with phenylalanine ammonia lyase (PAL), naturally encapsulated in plant cells, may provide a potential alternative treatment for hyperphenylalaninemic patients, including those with phenylketonuria. Therefore different sources of plant tissue were investigated for PAL activity.

RESULTS: Enzyme activity was highest in grain seedlings, with maximal enzyme activity in 7‐day‐old red spring wheat (Triticum aestivum L.) seedlings. The PAL activities of leaves and roots/endosperm of wheat seedlings were 11.90 ± 2.64 and 6.48 ± 1.59 µmol h−1 g−1 dry weight respectively. Three PAL‐related polypeptides with molecular weights of 74, 83 and 103 kDa were identified in wheat seedling leaf tissues, while only the 74 kDa polypeptide was detected in root/endosperm tissues. Dehydration was investigated as a method of concentrating PAL in wheat seedlings. Freeze‐drying was found to retain the most PAL activity (>90% recovery on a dry weight basis) compared with air drying and vacuum microwave drying for both leaf and root/endosperm samples.

CONCLUSION: This study has led to a better understanding of PAL activity and stability in plant tissues and provides the basis for developing a natural plant preparation as a dietary supplement for the treatment of hyperphenylalaninemia. Copyright © 2007 Society of Chemical Industry
Rats show differences in some biomarkers of health when eating diets based on ingredients produced with three different cultivation strategies
Authors: Lauridsen Charlotte , Yong Chen , Halekoh Ulrich , Bügel Susanne Højbjerg , Brandt Kirsten , Christensen Lars Porskjær , Jørgensen Henry
Published: December 2007

BACKGROUND: The aim of this study was to identify health‐related biomarkers affected by different growth conditions of plant foods. Rats were fed balanced diets composed of vegetables and rapeseed oil from three different cultivation systems (‘LIminusP’, low fertiliser input, without pesticides; ‘LIplusP’, low fertiliser input, with pesticides; and ‘HIplusP’, high fertiliser input, with pesticides) chosen to cover a broad range of management options, rather than representing actual food production systems.

RESULTS: Rats fed LIminusP and LIplusP had a higher serum IgG concentration compared to rats fed HIplusP and 14% less adipose tissue. Rats fed LIminusP showed less movement during the day than the other treatments, with no differences during the night. The liver metabolic function and free malonedialdehyde concentration differed between the LIminusP and the LIplusP treatments. Despite similar fatty acid composition and vitamin E content of the rapeseed oil used for the LIminusP and HIplusP diets, plasma concentrations of oleic and linoleic acids, γ‐ and α‐tocopherol and the liver concentration of lipid hydroperoxides differed between these two treatments.

CONCLUSION: Differences between dietary treatments composed of ingredients from different cultivation methods caused differences in some health‐related biomarkers, which, in future studies on this topic, should be assessed with respect to health implications. Copyright © 2007 Society of Chemical Industry
Chemical stability of haloperidol injection by high performance thin‐layer chromatography
Authors: Mennickent Sigrid , Pino Loreto , Vega Mario , de Diego Marta
Published: December 2007

The chemical stability of haloperidol lactate injection was studied under different storage conditions by high performance thin‐layer chromatography (HPTLC). The study was performed at 25 ± 2°C and at refrigeration temperature (8 ± 1°C) in original glass ampoules over 15 days after being opened. The samples tested at 25 ± 2°C were stored with exposure to and protection from light. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone/chloroform/n‐butanol/glacial acetic acid/water (5:10:10:2.5:2.5, v/v/v/v/v) as a mobile phase. Quantitative analyses were carried out at a wavelength of 254 nm. The method exhibited adequate linearity (r = 0.999), selectivity, precision (RSD = 1.92%), and accuracy (recoveries from 98.59 to 101.90%). The concentrations of all samples remained greater than or 90% of the original concentration. Haloperidol lactate injection was chemically stable under all conditions studied over 15 days.
Nanocellular Foams of PS/PMMA Polymer Blends
Authors: Otsuka Tetsuo , Taki Kentaro , Ohshima Masahiro
Published: December 2007

A nanocellular PS/PMMA polymer blend foam was prepared, where bubble nucleation was localized in the PMMA domains. The blend, which contains dispersed nanoscale PMMA islands, was prepared by polymerizing MMA monomers in a PS matrix to form highly dispersed PMMA domains in the PS matrix by diffusion mixing. The resulting blend was foamed with CO2 at room temperature. A higher depressurization rate at lower foaming temperature made the bubble diameter smaller and the bubble density larger, and a higher PS composition in the blend resulted in a larger bubble density. A void with 40–50 nm in average diameter and a pore density of 8.5 × 1014 cm−3 was obtained as for the finest nanocellular foams.

magnified image
Flavonoids as RTK inhibitors and potential anticancer agents
Authors: Teillet Florence , Boumendjel Ahcene , Boutonnat Jean , Ronot Xavier
Published: December 2007

Tyrosine kinase receptors (RTKs) play a crucial role in the regulation of the cell division cycle. Currently more than 50 RTKs divided into several subfamilies have been described. The inhibition of these enzymes has emerged as an important research‐area. Compounds able to inhibit the activity of these enzymes are expected to display antiproliferative properties. Flavonoids are representative of various small molecules acting as RTK inhibitors. These naturally occurring compounds are able to bind to the ATP‐binding site of several kinases. The most plausible current hypothesis explaining the action of these substances on kinases is that the chromenone moiety of the flavonoid acts as a mimetic of the adenine moiety of ATP, the receptor co‐factor. In this review, we report recent results on the activity of natural and synthetic derivatives of flavonoids as inhibitors of RTKs. Mechanistic aspects, the therapeutic usefulness, and the potential clinical use are discussed. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 5, 715–745, 2008
Global stability and the Hopf bifurcation for some class of delay differential equation
Authors: Bodnar Marek , Foryś Urszula
Published: December 2007

In this paper, we present an analysis for the class of delay differential equations with one discrete delay and the right‐hand side depending only on the past. We extend the results from paper by U. Foryś (Appl. Math. Lett. 2004; 17(5):581–584), where the right‐hand side is a unimodal function. In the performed analysis, we state more general conditions for global stability of the positive steady state and propose some conditions for the stable Hopf bifurcation occurring when this steady state looses stability. We illustrate the analysis by biological examples coming from the population dynamics. Copyright © 2007 John Wiley & Sons, Ltd.
Existence theorem and blow‐up criterion of the strong solutions to the magneto‐micropolar fluid equations
Authors: Yuan Jia
Published: December 2007

In this paper we study the magneto‐micropolar fluid equations in ℝ3, prove the existence of the strong solution with initial data inHs(ℝ3) for$s>{3\over2}$, and set up its blow‐up criterion. The tool we mainly use is Littlewood–Paley decomposition, by which we obtain a Beale–Kato–Majda‐type blow‐up criterion for smooth solution (u, ω,b) that relies on the vorticity of velocity ∇ × uonly. Copyright © 2007 John Wiley & Sons, Ltd.
The play operator on the rectifiable curves in a Hilbert space
Authors: Recupero Vincenzo
Published: December 2007

The vector play operator is the solution operator of a class of evolution variational inequalities arising in continuum mechanics. For regular data, the existence of solutions is easily obtained from general results on maximal monotone operators. If the datum is a continuous function of bounded variation, then the existence of a weak solution is usually proved by means of a time discretization procedure. In this paper we give a short proof of the existence of the play operator on rectifiable curves making use of basic facts of measure theory. We also drop the separability assumptions usually made by other authors. Copyright © 2007 John Wiley & Sons, Ltd.
A note on extinction for fast diffusive p‐Laplacian with sources
Authors: Liu Wenjun , Wu Bin
Published: December 2007

In this note we illuminate that the small condition on initial data u0 in Theorem 4.1 of Yin and Jin (Math. Meth. Appl. Sci. 2007; 30(10):1147–1167) can be removed for the case p−1<q<1. Precise decay estimates of solution are also obtained. Copyright © 2007 John Wiley & Sons, Ltd.
Correlations of dietary patterns with prostate health
Authors: Stacewicz‐Sapuntzakis Maria , Borthakur Gayatri , Burns James L. , Bowen Phyllis E.
Published: December 2007

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case‐control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low‐fat diets high in n‐3 fatty acids and increased risk with high‐fat diets rich in n‐6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve α‐methylacyl‐CoA racemase activity (required for β‐oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet‐risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.
Effect of muscle‐fiber velocity recovery function on motor unit action potential properties in voluntary contractions
Authors: Farina Dario , Falla Deborah
Published: December 2007

Measurements of muscle‐fiber conduction velocity during voluntary contractions have been used in the diagnosis of neuromuscular diseases. However, the velocity of propagation of action potentials depends on the interspike interval of activation due to the velocity recovery function (VRF) of muscle fibers. The comparison of muscle‐fiber conduction velocity estimates between individuals may thus be influenced by differences in motor unit discharge rate. This study investigates action potential properties of motor units of the sternocleidomastoid muscle during voluntary modulation of discharge rate with the purpose of assessing the effect of the VRF on motor unit properties in voluntary contractions. Nineteen healthy men trained to control a target motor unit with feedback of surface multichannel electromyographic (EMG) signals. The subjects performed three 30‐s contractions of cervical flexion/rotation modulating the discharge rate of the target motor unit from 6.6 ± 1.6 pps to 28.0 ± 6.4 pps. Action potential conduction velocity was correlated to instantaneous discharge rate (R = 0.38 ± 0.21). Action potential conduction velocity, peak‐to‐peak amplitude, and duration varied between minimum and maximum discharge rate (P < 0.01; percent change 12.3 ± 5.0, −11.8 ± 9.9, and −12.9 ± 7.3). Thus, the properties of surface motor unit action potentials vary with modulation of discharge rate. This has implications for the use of conduction velocity values measured during voluntary contractions to differentiate patient populations from healthy individuals and for the development of normative data. Muscle Nerve, 2008
A rotation‐free corotational plane beam element for non‐linear analyses
Authors: Battini Jean‐Marc
Published: December 2007

This paper presents a plane beam element without rotational degrees of freedom that can be used for the analysis of non‐linear problems. The element is based on two main ideas. First, a corotational approach is adopted, which means that the kinematics of the element is decomposed into a rigid body motion part and a deformational part. Next, in the deformational part, the local nodal rotations are extrapolated as a function of the local displacements of the two nodes of the element and the first nodes to the left and right of the element. Six numerical applications are presented in order to assess the performance of the formulation. Copyright © 2007 John Wiley & Sons, Ltd.
Preparation and electro‐optic properties of novel Y‐type polyimides with highly enhanced thermal stability of second harmonic generation
Authors: Jung Won‐Taek , Lee Ju‐Yeon , Won Dong‐Seon , Rhee Bum Ku
Published: December 2007

BACKGROUND: In the development of nonlinear optical (NLO) polymers for electro‐optic device applications, stabilization of electrically induced dipole alignment is one of the important criteria. Polyimides for NLO applications have attracted attention because of their high Tg values and high thermal stability. In this work we designed and synthesized a new type of NLO polyimide, in which the pendant NLO chromophores are parts of the polymer backbone. These mid‐type NLO polymers are expected to have the merits of both main‐chain and side‐chain NLO polymers: stabilization of dipole alignment and good solubility.

RESULTS: 3,4‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with the corresponding aromatic diamine to yield unprecedented Y‐type polyimides containing 3,4‐dioxynitrostilbenyl groups as NLO chromophores, which constituted parts of the polymer backbones. The resulting polyimides are soluble in polar solvents such as dimethylformamide and dimethylsulfoxide. These polymers showed a thermal stability up to 320 °C in thermogravimetric thermograms with Tg values obtained from differential scanning calorimetry thermograms in the range 143–164 °C. The second harmonic generation (SHG) coefficients (d33) of poled polymer films at the 1064 nm−1 fundamental wavelength were around 9.45 × 10−18 C.

CONCLUSION: The dipole alignment exhibited exceptionally high thermal stability even at 30 °C higher than Tg. There was no SHG decay below 180–190 °C because of the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. Copyright © 2007 Society of Chemical Industry
Understanding excitons in optically active polymers
Authors: Kirova Natasha
Published: December 2007

We review the solid‐state physics approach to electronic and optical properties of conducting polymers, and bring together the languages of solid‐state theory for polymers and the quantum chemistry of oligomers. We consider polymers as generic one‐dimensional semiconductors with specific features of strongly correlated electronic systems. Our model combines the large distance electron–hole motion within an exciton, governed by long‐range Coulomb attraction with strong intramonomer electronic correlations, which results in effective intramonomer electron–hole repulsion. We exploit the dielectric screening to go beyond the single chain picture and to compare excitons for polymers in solutions and in films. Our approach allows the connecting, explaining, exploiting and organizing of such different experimental and numerical findings as shallow singlet and deep triplet excitons in phenylenes, anomaly in singlet–triplet exciton formation ratio, Ag–Bu crossing in polyenes and common 1/N energy dependencies in oligomers. Copyright © 2007 Society of Chemical Industry
Morphology development and crystallization behavior of poly(ethylene terephthalate)/phenoxy blend
Authors: Kim Geon Seok , Lee Jong Kwan , Choi Mi Ju , Lee Kwang Hee
Published: December 2007

The morphological development and crystallization behavior of a poly(ethylene terephthalate)/poly(hydroxyl ether of bisphenol A) (phenoxy) blend were studied with time‐resolved light scattering, optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering (SAXS). During annealing at 280 °C, liquid–liquid phase separation via spinodal decomposition proceeded in the melt‐extruded specimen. After the formation of a domain structure, the blend slowly underwent phase homogenization by the interchange reactions between the two polymers. Specimens annealed for various times (ts) at 280 °C were subjected to a temperature drop and the effects of liquid‐phase changes on crystallization were then investigated. The shifts in the position of the cold‐crystallization peaks indicated that the crystallization rate is associated with the composition change of the separated phases as well as the change of the sequence distribution in polymer chains during annealing. The morphological parameters at the lamellar level were determined by a correlation function analysis on the SAXS data. The crystal thickness (lc) increased with ts, whereas the amorphous layer thickness (la) showed little dependence on ts. Observation of a constant la value revealed that a large number of noncrystallizable species formed by the interchange reactions between the two polymers were excluded from the lamellar stacks and resided in the interfibrillar regions, interspherulitic regions, or both. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 223–232, 2008
Simulation modelling to understand the evolution and management of glyphosate resistance in weeds
Authors: Neve Paul
Published: December 2007

BACKGROUND: A simulation model is used to explore the influence of biological, ecological, genetic and operational (management) factors on the probability and rate of glyphosate resistance in model weed species.

RESULTS: Glyphosate use for weed control prior to crop emergence is associated with low risks of resistance. These low risks can be further reduced by applying glyphosate in sequence with other broad‐spectrum herbicides prior to crop seeding. Post‐emergence glyphosate use, associated with glyphosate‐resistant crops, very significantly increases risks of resistance evolution. Annual rotation with conventional crops reduces these risks, but the proportion of resistant populations can only be reduced to close to zero by mixing two of three post‐emergence glyphosate applications with alternative herbicide modes of action. Weed species that are prolific seed producers with high seed bank turnover rates are most at risk of glyphosate resistance evolution. The model is especially sensitive to the initial frequency of R alleles, and other genetic and reproductive parameters, including weed breeding system, dominance of the resistance trait and relative fitness, influence rates of resistance.

CONCLUSION: Changing patterns of glyphosate use associated with glyphosate‐resistant crops are increasing risks of evolved glyphosate resistance. Strategies to mitigate these risks can be explored with simulation models. Models can also be used to identify weed species that are most at risk of evolving glyphosate resistance. Copyright © 2007 Society of Chemical Industry
Influence of imidacloprid seed treatments on rice germination and early seedling growth
Authors: Stevens Mark M , Reinke Russell F , Coombes Neil E , Helliwell Stuart , Mo Jianhua
Published: December 2007

BACKGROUND: Seed treatments with the chloronicotinyl insecticide imidacloprid (Gaucho® 600 FS) were evaluated to determine whether differences in concentration and exposure regime influence the germination and early growth of rice.

RESULTS: Continuous exposure to imidacloprid (4 days at 2000 mg AI L−1) significantly (P < 0.001) reduced normal germination by an average of 18% across the 15 cultivars examined. Nine days after sowing, plants showed no adverse effects from continuous imidacloprid treatment during germination, with shoot lengths and root system dry weights equalling, or occasionally exceeding (P < 0.05), those of untreated plants. Short‐term imidacloprid exposure (2 h at 2000 mg L−1) at initial seed wetting did not affect germination (P > 0.05), and short‐term (1 h) exposure of 48 h pregerminated seed to imidacloprid (2000 mg L−1) similarly had no significant effect on early subsequent growth. Plants arising from 48 h pregerminated seed exposed to imidacloprid (1 h) at concentrations up to 4000 mg L−1 immediately before sowing were not significantly different from control plants at either 9 or 25 days post‐sowing.

CONCLUSION: Results show that imidacloprid will have no adverse effects on plant growth if applied to pregerminated rice shortly before sowing. Continuous exposure of seed during germination had more pronounced effects, and the initial response of different cultivars was highly variable. Cultivars with high levels of sensitivity (such as IR72) require further testing before continuous exposure to imidacloprid during germination can be recommended. Copyright © 2007 Society of Chemical Industry
Managing the risk of glyphosate resistance in Australian glyphosate‐ resistant cotton production systems
Authors: Werth Jeff A , Preston Christopher , Taylor Ian N , Charles Graham W , Roberts Grant N , Baker Jeanine
Published: December 2007

BACKGROUND: Glyphosate‐resistant cotton varieties are an important tool for weed control in Australian cotton production systems. To increase the sustainability of this technology and to minimise the likelihood of resistance evolving through its use, weed scientists, together with herbicide regulators, industry representatives and the technology owners, have developed a framework that guides the use of the technology. Central to this framework is a crop management plan (CMP) and grower accreditation course. A simulation model that takes into account the characteristics of the weed species, initial gene frequencies and any associated fitness penalties was developed to ensure that the CMP was sufficiently robust to minimise resistance risks.

RESULTS: The simulations showed that, when a combination of weed control options was employed in addition to glyphosate, resistance did not evolve over the 30 year period of the simulation.

CONCLUSION: These simulations underline the importance of maintaining an integrated system for weed management to prevent the evolution of glyphosate resistance, prolonging the use of glyphosate‐resistant cotton. Copyright © 2007 Society of Chemical Industry
Pyrimidinyl‐substituted amides and thioureas: syntheses, crystal structure and herbicidal activities
Authors: Liu Guo‐Hua , Xue Yun‐Ning , Lu Xiao‐Quan , Liu Mou‐Ming , Wang Wei‐Ying , Yang Liang‐Zhun
Published: December 2007

BACKGROUND: The high herbicidal activities of [1,2,4]triazolo[1,5‐c]pyrimidine and 2H‐1,2,4‐thiadiazolo[2,3‐a]pyrimidine derivatives suggested the development of new fused heterocyclic compounds for application as herbicides.

RESULTS: Three series of pyrimidinyl‐substituted thioureas (4) and amides (5, 6) were synthesized, and the typical crystal structure of a 2H‐1,2,4‐thiadiazolo[2,3‐a]pyrimidine derivative (5a) was determined by X‐ray diffraction. All the compounds were tested for herbicidal activity against selected weeds.

CONCLUSION: The series of fused heterocyclic amides 5a to 5d exhibited high herbicidal activities both against monocotyledonous weeds (Echinochloa crus‐galli L., Sorghum bicolor (L.) Mönch., Digitaria sanguinalis (L.) Scop) and against dicotyledonous weeds (Amaranthus retroflexus L. and Brassica campestris L.) in pre‐emergence treatments. In particular, compound 5b at low concentration still showed high inhibitory activity against A. retroflexus in pre‐emergence treatment. Different substituents at the meta positions of the pyrimidine ring were found to affect the herbicidal activity. Copyright © 2007 Society of Chemical Industry
Aggregation and membrane permeabilizing properties of designed histidine‐containing cationic linear peptide antibiotics
Authors: Marquette Arnaud , Mason A. James , Bechinger Burkhard
Published: December 2007

Members of the LAH4 family of cationic linear peptide antibiotics have been designed to form amphipathic helical structures in membrane environments and switch from alignments parallel to the bilayer surface to transmembrane orientations in a pH‐dependent manner. Here the aggregation in aqueous buffer of two members of the family has been investigated by DLS. The peptides form monomers or small oligomers at pH = 5 but associate into nano‐sized aggregates at physiological pH. The diameter of these latter complexes can be considerably reduced by sonication. Furthermore, the membrane interactions of the various supramolecular aggregates with POPC or mixed POPC/POPS vesicles have been investigated in calcein‐release assays. In all the cases tested, the large preformed oligomeric peptide aggregates of 20–40 nm in size were more active than the structures with the smallest hydrodynamic radii in releasing the fluorescent dye from LUV. In contrast, the relative activity after sonication depends on the specific environment tested. The data suggest that these amphiphiles form micellar structures and support the notion that they can act in a manner comparable to detergents. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Liquid phase deposited silicon oxide with lower boron impurity grown on gallium nitride by temperature‐difference method
Authors: Lee Ming‐Kwei , Ho Chen‐Lin , Zeng Jia‐Yi
Published: December 2007

This study investigates the growth of silicon oxide film on gallium nitride using hydrosilicofluoric acid and silica gel by the temperature‐difference liquid‐phase deposition. In the conventional liquid phase deposition, the boric acid is used as fluorine scavenger to prompt silicon oxide deposition and it also acts as an impurity in the oxide film. The better metal–oxide–semiconductor diode electrical characteristics can be obtained by the temperature‐difference method with lower boric acid incorporation and higher deposition rate. Compared with the leakage current density of the conventional and temperature‐difference methods, it can be much improved from 9.93 × 10–2 A/cm2 to 5.8 × 10–4 A/cm2 at +2 MV/cm and from 1.35 × 10–2 A/cm2 to 5.15 × 10–4 A/cm2 at –1 MV/cm. The effective oxide charges is improved from 3.88 × 1011 cm–2 to 2.27 × 1011 cm–2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploring event‐related brain dynamics with tests on complex valued time–frequency representations
Authors: Martínez‐Montes Eduardo , Cuspineda‐Bravo Elena R. , El‐Deredy Wael , Sánchez‐Bornot José M. , Lage‐Castellanos Agustín , Valdés‐Sosa Pedro A.
Published: December 2007

A question subject to intense debate is whether scalp‐recorded event‐related brain potentials are due to phase resetting of the ongoing electroencephalogram (EEG) or rather to the superimposition of time‐locked components on background activity. The two hypotheses are usually assessed by means of statistics in the time–frequency domain, for example, through wavelet transformation of multiple EEG trials that yield for each time and frequency a scatter plot of complex values coefficients. Currently, intertrial phase correlation (phase locking or phase coherence) is taken as evidence for phase resetting at a given frequency and latency. Here we present a formal analysis using a complex t‐statistic to illustrate that such measures are, in effect, tests for the mean vector of the repeated trials, and as such on their own are inappropriate measures of phase resetting. We also propose simple t‐like statistics for testing changes in (i) the mean (presence of an event‐related potential), (ii) the amplitude variance (presence of (de)synchronization) and (iii) the concentration of phases (phase locking). The first two statistics are found to be proper measures of the presence of a non‐zero mean activity and induced activity, respectively. In the third case, two different tests are introduced: one based on measuring the alignment of coefficients in the complex plane and another derived from the argument that phase locking persists when the mean of the coefficients is removed. Both statistics gave unambiguous evidence of the presence of phase locking suggesting that they constitute promising tools in the analysis of event‐related brain dynamics. Copyright © 2007 John Wiley & Sons, Ltd.
Tuning mechanisms for two major parameters of Apache web servers
Authors: Sugiki Akiyoshi , Kono Kenji , Iwasaki Hideya
Published: December 2007

Apache web servers are widely used as stand‐alone servers or front‐ends in multi‐tiered web servers. Despite the wide availability of software, it is quite difficult for many administrators to properly configure their web servers. In particular, setting the performance‐related parameters is an error‐prone and time‐consuming task because their values heavily depend on the server environment. In this paper, two mechanisms are described for automatically tuning two performance‐related parameters of Apache web servers:KeepAliveTimeoutandMaxClients. These mechanisms are easy to deploy because no modifications to the server or the operating system are required. Moreover, they are parameter specific. Although interference betweenKeepAliveTimeoutandMaxClientsis inevitable, the tuning mechanisms minimize the correlation by using almost completely independent metrics. Experimental results show that these mechanisms work well for two different workloads; the parameter values are close to optimal and can adapt to workload changes. Copyright © 2007 John Wiley & Sons, Ltd.
In vivo measurement of nicotinic acetylcholine receptors with [18F]norchloro‐fluoro‐homoepibatidine
Authors: Brust Peter , Patt Jörg Thomas , Deuther‐Conrad Winnie , Becker Georg , Patt Marianne , Schildan Andreas , Sorger Dietlind , Kendziorra Kai , Meyer Philipp , Steinbach Jörg , Sabri Osama
Published: December 2007

Functional changes of nicotinic acetylcholine receptors (nAChR) are important during age‐related neuronal degeneration. Recent studies demonstrate the applicability of the nAChR ligand 2‐[18F]F‐A‐85380 for neuroimaging of patients with dementias. However, its binding kinetics demands a 7‐h acquisition time limiting its practicality for clinical PET studies. Thus, the authors developed [18F]norchloro‐fluoro‐homoepibatidine ([18F]NCFHEB) for nAChR imaging. The kinetics of the two enantiomers of [18F]NCFHEB were compared with 2‐[18F]F‐A85380 in porcine brain to evaluate their potential for human neuroimaging. Twenty‐four juvenile female pigs were studied with PET using [18F]NCFHEB. Nine animals received an additional i.v. injection (1 mg/kg) of the nAChR agonist A81418 before radiotracer administration followed by infusion (2 mg/kg/7h) thereafter. Several compartment models were applied for quantification. (−)‐ and (+)‐[18F]NCFHEB showed a twofold to threefold higher brain uptake than 2‐[18F]F‐A‐85380. All three radiotracers displayed spatially hetereogenous binding kinetics in regions with high, moderate, or low specific binding. The equilibrium of specific binding of (−)‐[18F]NCFHEB was reached earlier than that of (+)‐[18F]NCFHEB or 2‐[18F]F‐A85380. Continuous administration of the nAChR agonist A81418 inhibited the specific binding of (−)‐ and (+)‐[18F]NCFHEB but not of 2‐[18F]F‐A85380. The peripheral metabolism of (+)‐[18F]NCFHEB proceeded somewhat slower than that of the other radiotracers. Both enantiomers of [18F]NCFHEB are appropriate radiotracers for neuroimaging of nAChR in pigs. Their binding profile in vivo appears to be more selective than that of 2‐[18F]F‐A85380. (−)‐[18F]NCFHEB offers a faster equilibrium of specific binding than 2‐[18F]F‐A85380. Synapse 62:205–218, 2008. © 2007 Wiley‐Liss, Inc.