bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of spatially structured vegetation patterns on hillslope erosion in a semiarid Mediterranean environment: a simulation study
Authors: Boer Matthias , Puigdefábregas Juan
Published: February 2005

A general trend of decreasing soil loss rates with increasing vegetation cover fraction is widely accepted. Field observations and experimental work, however, show that the form of the cover‐erosion function can vary considerably, in particular for low cover conditions that prevail on arid and semiarid hillslopes. In this paper the structured spatial distribution of the vegetation cover and associated soil attributes is proposed as one of the possible causes of variation in cover–erosion relationships, in particular in dryland environments where patchy vegetation covers are common. A simulation approach was used to test the hypothesis that hillslope discharge and soil loss could be affected by variation in the spatial correlation structure of coupled vegetation cover and soil patterns alone. The Limburg Soil Erosion Model (LISEM) was parameterized and verified for a small catchment with discontinuous vegetation cover at Rambla Honda, SE Spain. Using the same parameter sets LISEM was subsequently used to simulate water and sediment fluxes on 1 ha hypothetical hillslopes with simulated spatial distributions of vegetation and soil parameters. Storms of constant rainfall intensity in the range of 30–70 mm h−1 and 10–30 min duration were applied. To quantify the effect of the spatial correlation structure of the vegetation and soil patterns, predicted discharge and soil loss rates from hillslopes with spatially structured distributions of vegetation and soil parameters were compared with those from hillslopes with spatially uniform distributions. The results showed that the spatial organization of bare and vegetated surfaces alone can have a substantial impact on predicted storm discharge and erosion. In general, water and sediment yields from hillslopes with spatially structured distributions of vegetation and soil parameters were greater than from identical hillslopes with spatially uniform distributions. Within a storm the effect of spatially structured vegetation and soil patterns was observed to be highly dynamic, and to depend on rainfall intensity and slope gradient. Copyright © 2005 John Wiley & Sons, Ltd.
The role of vegetation patterns in structuring runoff and sediment fluxes in drylands
Authors: Puigdefábregas Juan
Published: February 2005

The dynamics of vegetation‐driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps.

At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients.

At the stand scale within‐storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small‐grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them.

Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd.
Transgene expression and differentiation of baculovirus‐transduced human mesenchymal stem cells
Authors: Ho Yi‐Chen , Chung Yao‐Chi , Hwang Shiaw‐Min , Wang Kuei‐Chun , Hu Yu‐Chen
Published: February 2005

Background

Mesenchymal stem cells (MSCs) have drawn considerable attention as vehicles for cell‐ or gene‐based therapies, yet various problems still exist for current gene delivery vectors. On the other hand, baculovirus has emerged as a novel gene therapy vector, but its transduction of stem cells has not been reported.

Methods

A recombinant baculovirus expressing the enhanced green fluorescent protein (EGFP) was constructed to transduce human MSCs derived from umbilical cord blood (uMSCs) or bone marrow (bMSCs).

Results

In this study, we demonstrated for the first time that human uMSCs or bMSCs could be transduced by baculovirus with high efficiencies (up to ≈72.8% and 41.1%, respectively) and significantly elevated transgene (enhanced green fluorescent protein, EGFP) expression upon incubation with unconcentrated virus and phosphate‐buffered saline for 4 h at 25 °C. The transduction efficiency into bMSCs could be further increased to ≈72.2% by lowering the cell density. The improved transgene expression was partly attributed to the enhanced virus uptake upon transduction, as determined by quantitative real‐time polymerase chain reaction (Q‐PCR). MSC growth was not obstructed by baculovirus transduction itself, but was somewhat hampered by EGFP expression. Nonetheless, the baculovirus‐transduced cells remained capable of differentiating into adipogenic lineage. The adipogenic progenitors appeared more permissive to baculovirus transduction than the undifferentiated bMSCs, thus allowing for the maintenance and enhancement of transgene expression by repeated transduction after subculture.

Conclusions

These findings implicate the potential applications of baculovirus as an alternative vector to genetically modify MSCs for ex vivo gene therapy. Copyright © 2005 John Wiley & Sons, Ltd.
Nonviral genetic modification mediates effective transgene expression and functional RNA interference in human mesenchymal stem cells
Authors: Hoelters Juergen , Ciccarella Marisa , Drechsel Marei , Geissler Claudia , Gülkan Hülya , Böcker Wolfgang , Schieker Matthias , Jochum Marianne , Neth Peter
Published: February 2005

Background

Human mesenchymal stem cells (hMSC) are increasingly the focus of both basic and clinical research due to their ability to strike a balance between self‐renewal and commitment to mesodermal differentiation. However, the promising therapeutic utility of hMSC in regenerative medical approaches requires detailed knowledge about their molecular characteristics. Therefore, genetic modification of hMSC provides a powerful tool to understand their complex molecular regulation mechanisms.

Methods

Here we describe a proof of concept approach of separate and combined gene transfer and gene silencing by nonviral DNA transfection of enhanced green fluorescent protein (EGFP) and EGFP‐targeted small interfering RNAs (siRNAs) in hMSC. For optimization of nonviral DNA and siRNA transfer different liposomal‐based transfection strategies were validated.

Results

The highest fraction of EGFP‐expressing hMSC was obtained using Lipofectamine 2000 (50%) which also mediated the highest transfection rates of siRNAs into hMSC (≥92%). Stably EGFP‐expressing hMSC maintained their proliferation capacity paired with the ability to differentiate into different mesodermal lineages (bone, cartilage, and fat) without loss of transgene expression. Based on our nonviral nucleic acid delivery technique we showed efficient, functional, and long‐term RNA interference (RNAi) in hMSC by gene specific knock‐down of transiently and stably expressed EGFP (88–98%).

Conclusions

This is the first demonstration of efficient nonviral transfer of both nucleic acids (DNA and siRNA) into hMSC, exhibiting the potential of targeted modification of hMSC. In particular, the combination of these techniques represents a powerful gene transfer/silencing strategy, thus facilitating detailed genetic approaches to study regulatory networks in stem cell differentiation processes. Copyright © 2005 John Wiley & Sons, Ltd.
Long‐term expression of the human glucocerebrosidase gene in vivo after transplantation of bone‐marrow‐derived cells transformed with a lentivirus vector
Authors: Kim Eun Young , Hong Young Bin , Lai Zhennan , Cho Youl‐Hee , Brady Roscoe O. , Jung Sung‐Chul
Published: February 2005

Background

Gaucher disease is a lysosomal storage disorder resulting from a deficiency of glucocerebrosidase (GC). Recently, lentivirus vectors have been developed for efficient gene transfer into hematopoietic stem cells (HSCs). A recombinant lentivirus vector was used to evaluate the transduction of the human GC gene into murine bone‐marrow‐derived HSCs and its expression in their progeny.

Methods

Murine HSCs were transduced with lentivirus vector (lenti‐EF‐GC; MOI = 10–100). We transplanted female wild‐type C57BL/6J mice with genetically modified male HSCs via the tail vein.

Results

We show that intravenous transplantation of transduced HSCs has therapeutic potential. Enzyme activity was increased two‐ to three‐fold in various tissues, especially in the hematopoietic system. Numerous transplanted HSCs survived for 6 months and were shown by PCR to contain the provirus genes; the Y chromosome was identified by FISH analysis in the cells of female mouse recipients.

Conclusions

The recombinant lentiviral vector transduces HSCs that are capable of long‐term gene expression in vivo. This approach is potentially useful for the treatment of patents with Gaucher disease and other lysosomal storage disorders. Copyright © 2005 John Wiley & Sons, Ltd.
Combined immunization with fusion genes of mutated E7 gene of human papillomavirus type 16 did not enhance antitumor effect
Authors: Pokorná Dana , Macková Jana , Dušková Martina , Rittich Šimon , Ludvíková Viera , Šmahel Michal
Published: February 2005

Background

The E7 oncoprotein of human papillomavirus type 16 (HPV16) is frequently used as a model tumor‐associated antigen. Its immunogenicity has been substantially enhanced by fusion with several proteins of various origins and functions. Different mechanisms have been responsible for increased vaccination efficacy of fusion proteins.

Methods and results

We linked E7 and its mutated form (E7GGG) with the mouse heat‐shock protein 70.1 (HSP70.1). Enhanced immunogenicity of both fusion genes administered via a gene gun was demonstrated by protection of C57BL/6 mice against oncogenic MHC class I positive TC‐1 cells producing the HPV16 E7 oncoprotein but not against the MHC class I negative TC‐1/A9 subline. To assess if the efficacy of E7‐based DNA vaccines could be increased by combination of various fusion genes, we combined the HSP70.1 fusion genes (i.e. E7HSP or E7GGGHSP) with the fusion construct linking E7GGG with targeting signals of lysosome‐associated membrane protein 1 (Sig/E7GGG/LAMP‐1). Treatment of mice 4 days after TC‐1 cell inoculation showed moderately higher immunization potency of HSP70.1 fusion genes in comparison with the Sig/E7GGG/LAMP‐1 gene. Any combination of two fusion genes given in the same gene gun shot neither was more effective compared with single genes nor protected mice against TC‐1/A9 cells. As fusion of E7GGG with E. coli glucuronidase (E7GGG.GUS) had been previously proven to provide partial protection from TC‐1/A9‐induced tumors, we also combined E7GGGHSP with E7GGG.GUS. The genes were inoculated either in mix in two gene gun shots or separately each gene in one shot into opposite sides of the abdomen. Neither mode of combined immunization induced higher protection than E7GGG.GUS alone. However, doubling the DNA dose considerably enhanced the antitumor efficacy of E7GGG.GUS.

Conclusions

We constructed highly immunogenic fusions of HPV16 E7 and E7GGG with mouse HSP70.1. Furthermore, we substantially enhanced protection against TC‐1/A9 cells with downregulated MHC class I expression by doubling the pBSC/E7GGG.GUS dose, but we failed to demonstrate a beneficial effect of any combination of two fusion genes with different mechanisms causing enhancement of HPV16 E7 immunogenicity. Copyright © 2005 John Wiley & Sons, Ltd.
Modelling the deformation mechanisms, structure–property relationships and applications of auxetic nanomaterials
Authors: Alderson A. , Alderson K. L. , Evans K. E. , Grima J. N. , Williams M. R. , Davies P. J.
Published: February 2005

Analytical and Molecular Mechanics methods have been used to study the structure and deformation mechanisms acting at the molecular level in the auxetic polymorph of crystalline silica (α‐cristobalite). The Molecular Mechanics simulations indicate a stress‐induced phase transition from α‐cristobalite to ‘ordered’ β‐cristobalite occurs for uniaxial loading along the x3 direction. This is in reasonable agreement with the previous prediction from an analytical model assuming deformation is by concurrent dilation and cooperative rotation (about axes in the x1‐x2 plane, passing through the midpoints of opposing edges – the a‐axes) of the SiO4 tetrahedral molecular sub‐units, previously shown to predict the Poisson's ratio for loading in the x3 direction. The analytical models have been extended to include cooperative rotation of each tetrahedron about its axis (the c‐axis) mostly closely aligned with the principal unit‐cell x3‐axis. The new models enable significantly improved prediction of the Poisson's ratios of α‐cristobalite when loaded in one of the transverse (x1 or x2) directions. Parametric fitting of the analytical models indicate that the deformation mechanism for transverse uniaxial loading of α‐cristobalite is by concurrent dilation and cooperative rotation about the local a and c‐axes of the SiO4 tetrahedra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deformation degree estimators for several basic structural units in numerically simulated materials
Authors: Bergmanski G. , Bialoskórski M. , Rybicki J. , Feliziani S.
Published: February 2005

In the paper we introduce several deformation degree estimators for a series of basic structural units, CAn (C – cation, A – anion), often encountered in numerically simulated solids. We apply Monte Carlo simulations to calculate the distributions of the estimators' values in the function of the polyhedra deformation degree. The obtained model results provide reference data that may be useful for quantitative analysis of short range correlations in materials' structures obtained with the aid of computer simulations, e.g. Molecular Dynamics. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the elastic contribution to crystal growth in complex environments
Authors: Gadomski A. , Siódmiak J.
Published: February 2005

Based on a number of experimental studies, we propose to consider how elastic interactions between a crystal and its surroundings change crystal growing conditions. To aim to do this, we analyze the influence of some nonequilibrium modification of the Gibbs–Thomson thermodynamic condition, prescribed at the crystal boundary, on some properties of a kinetic model of protein crystal growth in a mass‐convection regime. Next, to draw the physical picture more realistically, we study the influence of a certain stochastic perturbation on the crystal growth rate. To fulfill the task we apply the description of crystal growth in terms of nonequilibrium thermodynamics at a mesoscopic level. The proposed model offers a quite comprehensive picture of the formation of modern organic crystalline materials such as non‐Kossel crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal expansion and contraction of polymer thin films
Authors: Kanaya T. , Miyazaki T. , Inoue R. , Nishida K.
Published: February 2005

We have studied thermal expansion and contraction of polystyrene thin film supported on silicon substrate using X‐ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we found fast and very slow contraction processes in the thin films above the glass transition temperature. The fast one was attributed to normal relaxation (annealing) process observed in bulk and responsible partly for the reported apparent negative expansivity. In addition, we found extremely slow re‐expansion process in the glassy state. The ultra‐slow contraction and re‐expansion have been assigned to the lateral expansion and contraction of the film, respectively. Using well‐annealed films, we have evaluated thermal expansivity as a function of film thickness, and found that it decreases with film thickness in a thickness range below twice of radius of gyration of a polymer chain 2Rg in the glassy state. The decrease has been attributed to hardening of harmonic force constant due to confinement in a thin film. This idea was confirmed in the inelastic neutron scattering measurements. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extreme viscoelastic properties of composites of strongly inhomogeneous structures due to negative stiffness phases
Authors: Novikov V. V. , Wojciechowski K. W.
Published: February 2005

A fractal model of structure [V. V. Novikov et al., Phys. Rev. E 63, 036120 (2001)] is generalized and applied to study the viscoelastic properties of a two‐component, strongly inhomogeneous medium of chaotic structure with one component exhibiting a negative shear modulus. It is shown that similar to the results obtained recently in frames of the Hashin–Strikman model [R. S. Lakes, Phys. Rev. Lett. 86, 2897 (2001)], the present fractal model predicts the existence of composites having effective shear and damping coefficients much higher than those of the component phases. The viscoelastic properties of the strongly inhomogeneous medium are, however, qualitatively different from the properties of the Hashin‐Strikman medium. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Directional and band‐gap behavior of periodic auxetic lattices
Authors: Ruzzene M. , Scarpa F.
Published: February 2005

The paper investigates the wave propagation characteristics of periodic two dimensional, auxetic lattice structures. Periodic structures in general feature unique wave propagation characteristics, whereby waves are allowed to propagate only within specific frequency bands. Two dimensional periodic structures complement this feature with a low frequency directional behavior. The combination of these unique characteristics makes two dimensional periodic structures ideal candidates for the design of pass‐band directional mechanical filters.

Focus is here placed on honeycomb lattice configurations. A sensitivity analysis is first presented to investigate the influence of band‐gap and directional behaviors with respect to changes in the internal angle. The presented results demonstrate how re‐entrant topologies feature enhanced wave attenuation capabilities with respect to hexagonal lay‐outs. An optimization problem is then formulated by considering the internal angle as a design variable, and the width of the attenuation frequency ranges and angular range of propagation at low frequencies as objective functions. The identified optimal configurations feature combined properties which demonstrate the effectiveness of the analysis procedure. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Auxetic compliant flexible PU foams: static and dynamic properties
Authors: Scarpa F. , Pastorino P. , Garelli A. , Patsias S. , Ruzzene M.
Published: February 2005

The paper describes the manufacturing and tensile testing of auxetic (negative Poisson's ratio) thermoplastic polyurethane foams, both under constant strain rate and sinusoidal excitation. The foams are produced from conventional flexible polyurethane basis following a manufacturing route developed in previous works. The Poisson's ratio behaviour over tensile strain has been analyzed using an Image Data processing technique based on Edge Detection from digital images recorded during quasi‐static tensile test. The samples have been subjected to tensile and compressive tests at quasi‐static and constant strain‐rate values (up to 12 s–1). Analogous tests have been performed over iso‐volumetric foams samples, i.e., foams subjected to the same volumetric compression of the auxetic ones, exhibiting a near zero Poisson's ratio behaviour. The auxetic and non‐auxetic foams have been also tested under sinusoidal cycling load up to 10 Hz, with maximum pre‐strain applied of 12%. The hysteresis of the cycling loading curve has been measured to determine the damping hysteretic loss factor for the various foams. The measurements indicate that auxetic foams have increased damping loss factor of 20% compared to the conventional foams. The energy dissipation is particularly relevant in the tensile segment of the curve, with effects given by the pre‐strain level imposed on the samples. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global and local linear buckling behavior of a chiral cellular structure
Authors: Spadoni A. , Ruzzene M. , Scarpa F.
Published: February 2005

This paper investigates the flat‐wise compression behavior of an innovative cellular structure configuration. The considered layout has a hexagonal chiral geometry featuring cylinders, or nodes, joined by ligaments, or ribs. The resulting assembly is characterized by a number of interesting properties that can be exploited for the design of alternative honeycombs or cellular topologies to be used in sandwich construction. The flat‐wise strength of the chiral geometry is investigated through classical analytical formulas for the linear buckling of thin plates and shells and a bifurcation analysis performed on a Finite Element model. The analytical expressions predict the global buckling behavior and the resulting critical loads, and can be directly compared with the results obtained from the Finite Element analysis. In addition, the Finite Element model predicts local buckling modes, which should be considered to evaluate the possible development of localized plasticity. A sensitivity study is performed to evaluate the influence of the geometry of the chiral structure on its buckling strength. The study shows that the considered topology can offer great design flexibility, whereby several parameters can be selected and modified to improve the flat‐wise performance. The comparison with traditional, hexagonal centro‐symmetric structural configurations concludes the paper and demonstrates the enhanced performance and the potentials of chiral noncentro‐symmetric designs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo simulation of two‐dimensional hard body systems with extreme values of the Poisson's ratio
Authors: Tretiakov K. V. , Wojciechowski K. W.
Published: February 2005

Monte Carlo computer simulations with variable shape of the periodic box were performed for a few two‐dimensional, hard‐body models showing elastically isotropic solid phases. Two examples of homo‐molecular (i.e. consisting of identical molecules) systems of anisotropic molecules are discussed which form unusual solid phases, showing negative Poisson's ratio and know as auxetic ones, at densities and pressures higher than the elastically isotropic solid phases. Sharp extremes of the Poisson's ratio were observed for both systems at freezing of the orientational degrees of freedom of the molecules: a minimum was observed for the system for which the auxetic phase with frozen rotation is isotropic and a maximum was found for the other system. This indicates that isotropic auxetic phases can have auxetic precursors with much more negative Poisson's ratios than those characterizing the auxetic phases themselves. An example of a hetero‐molecular (i.e. mixture consisting of different molecules), elastically isotropic system is also discussed – the polydisperse hard disc system. The simulations revealed a maximum of the Poisson's ratio in the close packing limit at any nonzero polydispersity. Although no manifestation of any auxetic behaviour has been found in this system, the obtained results indicate other unusual effect – a jump (discontinuity) of the Poisson's ratio at close packing when the polydispersity tends to zero. The results obtained in this work demonstrate that the Poisson's ratio can play the role of a sensitive indicator of (at least) some structural changes in solids. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of auxetic polymer self‐assemblies
Authors: Wei Gaoyuan
Published: February 2005

Alternating copolymers having a double‐arrow‐like “hard” block and a spring‐like “soft” segment have been designed which can in principle self‐assembly into two‐dimensional supramolecular networks. Molecular‐mechanics calculations show that such self‐assemblies can be auxetic when the lengths of the block and the segment are carefully chosen, with one metastable supermolecule having one of its six Poisson ratios as negatively large as –11.86. The underlying principle of designing such auxetic self‐assembly of copolymers with specified architecture is also given as are the deciding factors such as the packing geometry and the associated lattice energy in achieving the auxeticity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Liquids at negative pressure
Authors: Xiao C. , Heyes D. M. , Powles J. G.
Published: February 2005

We have further explored the final stages of the collapse of an unstable cavity or bubble using the Molecular Dynamics computer simulation technique. A nanometre sized spherical volume of molecules was removed from a bulk Lennard–Jones liquid, which being mechanically and thermodynamically unstable, proceeded to collapse. The molecules with the highest kinetic energy were the first to enter the initially empty cavity. The temperature of individual molecules inside the cavity, while the density was still typical of a gas, could reach at least an order of magnitude larger than that of the surrounding liquid, e.g., equivalent to 6,000 K for water, which is not unreasonable for the sonoluminescence effect to be seen. During the filling in of the cavity, the average temperature decreased, as the contents thermally equilibrated with the surrounding liquid. The bubble partially filled in, and then proceeded to partially empty again, and so on in an oscillatory manner, with ever decreasing amplitude towards the final uniform liquid state. This ‘recoil’ effect is predicted by classical hydrodynamic treatments and has been observed in experiment for much larger bubbles. The temperature, density and normal pressure component were resolved as a function of radius from the centre of the bubble at selected times during the collapsing process. The simulations support the view that MD can provide a realistic representation of the final stages of cavity collapse. It does not make assumptions about equation of state and transport coefficients as would be required for a comparable solution of the Navier–Stokes hydrodynamics equations, and is therefore an especially appropriate description for the final stages of the collapse. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Toward molecular auxetics: Main chain liquid crystalline polymers consisting of laterally attached para‐quaterphenyls
Authors: He Chaobin , Liu Puwei , McMullan Philip J. , Griffin Anselm C.
Published: February 2005

Polymers containing para‐quaterphenyl rods laterally attached to the polymer main chain have been synthesized. The molecular design choices which led to use of the quaterphenyl rod to achieve auxetic response will be discussed. Preparative chemistry of the monomers will be described along with the details of the polymerization reaction. Both polyethers and polyesters were prepared. The length of the flexible alkyl main chains which link the rods plays an important role in determining whether the resulting polymers will exhibit liquid crystallinity. Polymers with longer alkyl links exhibit nematic liquid crystallinity and the rods appear to have their long axes oriented roughly parallel and along the main chain direction. X‐ray scattering experiments were performed on the polymers both in the quiescent (unstretched) and the stretched states. Results from these experiments suggest that, under tensile strain, site connectivity driven rod‐reorientation occurs in these materials giving rise to an increase in the interchain distance for these polymers. This increase in the interchain separation is consistent with our concept of a molecular level auxetic mechanism for this type of designed polymer. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Al‐based systems with unusual mechanical and transport properties
Authors: Müllerová K. , Kovácik J. , Simancík F. , Švec P.
Published: February 2005

Addition of selected transition‐metal elements into aluminum matrix is known to yield systems that exhibit unique structural arrangements and mechanical properties, especially high yield strength obtained after suitable heat treatment. These lightweight systems are known to be compactable from ribbon shape prepared by rapid quenching of the melt into bulk form, yielding physically and technically attractive materials. The combination of knowledge about formation of aluminum‐based foams with the physics of rapid quenching and compaction is shown as a possible route for approaching the preparation of lightweight materials with potentially auxetic behavior. Enhancement of this property is discussed briefly in terms of tailoring the network or cell‐pore structure of different dimensions, ranging from millimeters down to nanoscale and sub‐nanoscale atomic ordering. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decomposition of protonated noradrenaline and normetanephrine assisted by NH2 migration studied by electrospray tandem mass spectrometry and molecular orbital calculations
Authors: Rogalewicz Françoise , Bourcier Sophie , Hoppilliard Yannik
Published: February 2005

As part of a research program on neurotransmitters in a biological fluid, the fragmentations characterising catecholamines protonated under electrospray ionisation (ESI) conditions, under low collision energy in a triple‐quadrupole mass spectrometer, were investigated. The decompositions of protonated noradrenaline (VH) and normetanephrine (VIH) were studied. Both precursor ions eliminate first H2O at very low collision energy, and the fragmentations of [MH–H2O]+ occur at higher collision energy. The breakdown graphs of [MH–H2O]+ ions, with collision energy varying from 0–40 eV in the laboratory frame, are presented. [VIH–H2O]+ ions lose competitively NH3 and CH3OH. For [VH–H2O]+ the loss of NH3 is dominant while H2O is eliminated at very low abundance at all collision energies. All of these secondary fragmentations are followed at higher collision energies by elimination of CO. These fragmentations are interpreted by means of ab initio calculations up to the B3LYP/6‐311+G(2d,2p) level of theory. The elimination of H2O requires first the isomerisation of N‐protonated forms, chosen as energy references, to O‐protonated forms. The isomerisation barriers are calculated to be lower than 81 kJ/mol above the N‐protonated forms. The elimination of NH3 from [MH–H2O]+ requires first the migration, via a cyclisation, of the amine function from the linear chain to the aromatic ring in order to prevent the formation of unstable disubstituted carbocations in the ring. The barriers associated with the loss of NH3 are located 220 and 233 kJ/mol above VH and 219 kJ/mol above VIH. The energy barrier for the loss of ROH is located 236 and 228 kJ/mol above VH and VIH, respectively. The absence of ions corresponding to [VH–2H2O]+ is due to a parasitic mechanism with an activation barrier lower than 236 kJ/mol that leads to a stable species unable to fragment, thus preventing the second loss of H2O. Losses of CO following the secondary fragmentations involve activation barriers higher than 330 kJ/mol. Copyright © 2005 John Wiley & Sons, Ltd.
Determination of amphetamine, methamphetamine, 3,4‐methylenedioxyamphetamine, 3,4‐methylenedioxyethylamphetamine, and 3,4‐methylenedioxymethamphetamine in urine by online solid‐phase extraction and ion‐pairing liquid chromatography with detection by electrospray tandem mass spectrometry
Authors: Wu Ti‐Yu , Fuh Ming‐Ren
Published: February 2005

A method using an online solid‐phase extraction (SPE) and ion‐pairing liquid chromatography with electrospray tandem mass spectrometry (LC/ES‐MS/MS) was developed for determination of amphetamine (Amp), methamphetamine (mAmp), 3,4‐methylenedioxyamphetamine (MDA), 3,4‐methylenedioxyethylamphetamine (MDEA), and 3,4‐methylenedioxymethamphetamine (MDMA) in urine samples. A SPE cartridge column with both hydrophilic and lipophilic functions was utilized for online extraction. A reversed‐phase C18 LC column was employed for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion‐pairing reagent. This method was fully automated and the extraction and analysis procedures were controlled by a six‐port switch valve. Recoveries ranging from 85–101% were measured. Good linear ranges (10–500 ng/mL) for Amp and mAmp were determined. For MDA, MDMA and MDEA, dual linear ranges were obtained from 5–100 and 100–500 ng/mL, respectively. The detection limit of each analytical compound, based on a signal‐to‐noise ratio of 3, ranged from 1–3 ng/mL. The applicability of this newly developed method was examined by analyzing several urine samples from drug users. Good agreement was obtained between the results from this method and a literature GC/MS method. Copyright © 2005 John Wiley & Sons, Ltd.
The use of the propensity score for estimating treatment effects: administrative versus clinical data
Authors: Austin Peter C. , Mamdani Muhammad M. , Stukel Therese A. , Anderson Geoffrey M. , Tu Jack V.
Published: February 2005

There is an increasing interest in using administrative data to estimate the treatment effects of interventions. While administrative data are relatively inexpensive to obtain and provide population coverage, they are frequently characterized by lack of clinical detail, often leading to problematic confounding when they are used to conduct observational research. Propensity score methods are increasingly being used to address confounding in estimating the effects of interventions in such studies. Using data on patients discharged from hospital for whom both administrative data and detailed clinical data obtained from chart reviews were available, we examined the degree to which stratifying on the quintiles of propensity scores derived from administrative data was able to balance patient characteristics measured in clinical data. We also determined the extent to which measures of treatment effect obtained using propensity score methods were similar to those obtained using traditional regression methods. As a test case, we examined the treatment effects of ASA and beta‐blockers following acute myocardial infarction. We demonstrated that propensity scores developed using administrative data do not necessarily balance patient characteristics contained in clinical data. Furthermore, measures of treatment effectiveness were attenuated when obtained using clinical data compared to when administrative data were used. Copyright © 2005 John Wiley & Sons, Ltd.
Repeat Pulmonary Resection for Isolated Recurrent Lung Metastases Yields Results Comparable to Those after First Pulmonary Resection in Colorectal Cancer
Authors: Ogata Yutaka , Matono Keiko , Hayashi Akihiro , Takamor Shinzo , Miwa Keisuke , Sasatomi Teruo , Ishibashi Nobuya , Shida Seiichiro , Shirouzu Kazuo
Published: February 2005

Pulmonary resection for colorectal metastases is well accepted. However, the main cause of death after pulmonary resection is recurrence in the lung. The aim of this study was to clarify whether a repeat pulmonary resection was warranted in patients with recurrent lung metastases. The records of 76 patients undergoing initial pulmonary resection, including 14 patients undergoing a repeat operation for lung metastases, were reviewed for survival, operative morbidity, and mortality. Overall, pulmonary resection was performed 96 times in this group of patients. The operative mortality was 0%, morbidity involved only one case of major postoperative hemorrhage associated with the first operation. The cumulative 5‐year survival rate for the 76 patients was 32%. After the second pulmonary operation, recurrence was identified in 79% (11 of 14) of the patients. In 10 patients with isolated lung recurrence after a first pulmonary resection, who showed no extrapulmonary disease before or at the time of first thoracotomy, the 3‐year, and 5‐year‐survival rate after the second pulmonary resection was 67%, and 33%, respectively, comparing favorably with the survival rate in those who underwent primary pulmonary resection. In contrast, all 4 patients with extrapulmonary disease before or at the time of thoracotomy had poor prognosis. Repeat pulmonary operation for isolated recurrent colorectal metastases to the lung yielded results comparable to those after the first pulmonary resection in terms of operative mortality and survival in the absence of hilar/mediastinal lymph node or extrathoracic involvement.
Somatostatin, Somatostatin Receptors, and Pancreatic Cancer
Authors: Li Min , Fisher William E. , Kim Hee Joon , Wang Xiaoping , Brunicardi Charles F. , Chen Changyi , Yao Qizhi
Published: February 2005

Somatostatin may play an important role in the regulation of cancer growth including pancreatic cancer by interaction with somatostatin receptors (SSTRs) on the cell surface. Five SSTRs were cloned, and the function of these SSTRs is addressed in this review. SSTR‐2, SSTR‐5, and SSTR‐1 are thought to play major roles in inhibiting pancreatic cancer growth both in vitro and in vivo. SSTR‐3 may be involved in mediating apoptosis, but the role of SSTR‐4 is not clear. In most pancreatic cancers, functional SSTRs are absent. Reintroduction of SSTR genes has been shown to inhibit pancreatic cancer growth in cell cultures and animal models.
Role of Proteases in Pancreatic Carcinoma
Authors: Patten Lane C. , Berger David H.
Published: February 2005

Proteases play an important role in cancer invasion and metastasis. In this review we specifically discuss the role of these proteases in pancreatic carcinoma. Serine proteases and matrix metalloproteinases are the focus of intense research, as they appear to be related to the process of tumor progression. We discuss the diagnostic and prognostic value of these two groups of proteases. Lastly, we report on the current and recent clinical trials focusing on inhibition of these proteases.
Abrogation of Transforming Growth Factor‐β Signaling in Pancreatic Cancer
Authors: Lin Xia , Feng Xin‐Hua
Published: February 2005

Transforming growth factor‐β (TGFβ) functions as a growth inhibitor for many cell types by inhibiting cell cycle progression. Loss of TGFβ responsiveness can lead to deregulated cell proliferation and ultimately tumor progression. For example, the TGFβ signaling pathway is a frequent target for inactivation in pancreatic cancer. Functional connection between the potent growth inhibitory activity of TGFβ and the tumor suppressor activity of Smads has been well documented. Smads directly modulate transcription of the genes involved in cell cycle progression in response to TGFβ, and that abrogation of this regulation leads to tumor progression. In this review, we summarize recent research progress on TGFβ signaling and pancreatic cancer.
Effects of number of flowers per raceme and number of racemes per plant on bumblebee visits and female reproductive success in Salvia nipponica (Labiatae)
Authors: Miyake Yasuko C. , Sakai Satoki
Published: February 2005

We studied the adaptive arrangement of raceme flowers in dense and sparse habitats of Salvia nipponica. We recorded bumblebee visits and collected mature seeds to estimate outcrossing rates from allozyme genotypes. To examine the resource investment in flowering stalks, we measured their length and dry mass. We found that a greater number of open flowers in a raceme enhanced bumblebee visits and successive probings in both density plots. However, greater height of a raceme did not enhance these in plots of either density. In the high‐density plot, both a greater mean number of open flowers in a raceme and a greater number of flowering racemes on a plant enhanced bumblebee visits, successive probings, and also enhanced outcrossing rate in spite of an increase in successive probings. Although the number of flowers per raceme had a greater positive effect on seed‐to‐ovule ratios than did the number of racemes, the number of flowers per raceme may be constrained because a longer flowering stalk needs greater buckling strength. Hence, it may be advantageous for plants in high‐density plots to increase both number of flowers per raceme and number of racemes. In the low‐density plot, a greater number of flowering racemes on a plant enhanced pollinator visits, but a greater mean number of open flowers in a raceme did not. Hence, it may be advantageous for plants to increase the number of racemes while keeping the numbers of flowers per raceme small. Thus, the adaptive number of flowers per raceme and number of racemes per plant may differ between high‐ and low‐density plots.
Characterization of the interactions between stromal and haematopoietic progenitor cells in expansion cell culture models
Authors: Bilko N.M. , Votyakova I.A. , Vasylovska S.V. , Bilko D.I.
Published: February 2005

Development of the long‐term culture models of haematopoietic stem cells (HSCs) is one of the important tasks in modern biotechnology. It has been suggested that stromal presence is important for haematopoiesis in vitro and in vivo, but the question remains: whether diffusible factors produced by stromal cells are sufficient for the regeneration of primitive and definitive haematopoietic cells, or direct cell‐to‐cell contacts of the cultured material with underlying stromal base would be required. During present studies, influence of various feeder layers and feeder layer conditioned media on proliferative, differentiative and clonogenic activity of human AC133+ derived from human umbilical cord blood was investigated. Cell extracts for feeder layers were prepared from 4–6 weeks old human embryos and co‐cultured feeder cells. Effects of the conditioned media were also determined. Culture and feeder layer media were additionally supplemented with commonly implemented factors such as GM‐CSF, IL‐3 and LIF. Estimation of morpho‐functional properties of AC133+ cultivated suspension cultures was performed in subculture experiments using semisolid agar culture conditions. Multipotential CFU‐MIX (CFU‐GEMM) and unipotential progenitor cells CFU‐GM, BFU‐E and CFU‐E were observed and analyzed. Our data suggest that haematopoiesis can be sustained for prolonged cultivation periods in the presence of feeder layer cells or conditioned media supported culture models. Prolonged support of primitive haematopoietic cells and their clonogenic capacity and functional characteristics in feeder layer positive cultures, indicates that diffusible factors are sufficient for haematopoiesis and suggests that direct cell‐to‐cell contacts may not be exclusively required for successful long‐term in vitro haematopoiesis.
Psycho‐social factors and coping strategies as predictors of chronic evolution and quality of life in patients with low back pain: A prospective study
Authors: Koleck Michèle , Mazaux Jean‐Michel , Rascle Nicole , Bruchon‐Schweitzer Marilou
Published: February 2005

Low back pain (LBP) is a major problem of public health. Chronic pain is the most difficult to treat and the most expensive. The way patients cope with their pain may influence its outcome.

Aim: To identify coping strategies of LBP patients, and their influence on LBP evolution.

Methods: Ninety nine patients were assessed just after an acute LBP episode and one year later. Assessment tools included medical and social reports, scales of anxiety, depression, quality of life, locus of control (LOC), social support and coping strategies.

Results: One year after the initial episode, 67% of patients have improved and 33% had a chronic pain. A principal components analysis showed that two main dimensions might be identified inside the outcome: functional and emotional non‐adjustment. Functional non‐adjustment was predicted by male gender, reduction of activity, and history of trauma over one year. Emotional non‐adjustment was only predicted by trait‐depression. Reactions to pain were structured in four factors: distraction‐praying, helplessness‐hopelessness, cognitive restructuration and perceived control. Two of these factors predicted adjustment one year later: distraction‐praying had a direct effect on functional non‐adjustment, and helplessness‐hopelessness on emotional issue.

Conclusions: Besides somatic factors, psychosocial predictors of LBP chronic evolution may be identified. Both aspects must be taken into account in order to prevent chronic pain. Perhaps cognitive‐behavior therapy may help LBP patients to cope with pain in a better way.
Pathway information for systems biology
Authors: Cary Michael P. , Bader Gary D. , Sander Chris
Published: February 2005

Pathway information is vital for successful quantitative modeling of biological systems. The almost 170 online pathway databases vary widely in coverage and representation of biological processes, making their use extremely difficult. Future pathway information systems for querying, visualization and analysis must support standard exchange formats to successfully integrate data on a large scale. Such integrated systems will greatly facilitate the constructive cycle of computational model building and experimental verification that lies at the heart of systems biology.
Antarctic ecosystem monitoring: quantifying the response of ecosystem indicators to variability in Antarctic krill
Authors: Reid Keith , Croxall John P. , Briggs Dirk R. , Murphy Eugene J.
Published: February 2005

The utility of upper-trophic-level species as ecosystem indicators is determined by our ability to relate changes in indices of their performance to changes at lower trophic levels. Such relationships were assessed using indices of predator performance (response vectors) for four predator species, together with independent ship-based acoustic estimates of abundance of their main prey, Antarctic krill (Euphausia superba), from South Georgia in the South Atlantic Ocean. Out of 32 response vectors investigated, 13 showed a significant non-linear relationship, based on a Holling Type II response, to krill abundance, and just five showed a significant linear relationship. Predator responses reflecting the processes during summer, when prey surveys were undertaken, showed the closest relationship with prey abundance. Distinct relationships existed between the variability of indices and the biological processes they measured. Body mass variables had the lowest variability (CVs <10%), whereas those measuring breeding success showed the greatest variability (CVs >50%). Multivariate indices, produced by combining response vectors from all four predator species into a single combined index, provided a better fit with krill data than any of the individual vectors. Whereas population size parameters for individual species showed no relationship with annual estimates of krill abundance, a combined, multispecies population size index did show a significant response. Understanding the form of the relationship between concurrent indicators of prey abundance and key ecosystem metrics/reference points, such as population size, is crucial to the application of monitoring data to management action.