bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoporous Low‐κ Polyimide Films via Poly(amic acid)s with Grafted Poly(ethylene glycol) Side Chains from a Reversible Addition–Fragmentation Chain‐Transfer‐Mediated Process
Authors: Chen Y. , Wang W. , Yu W. , Yuan Z. , Kang E.‐T. , Neoh K.‐G. , Krauter B. , Greiner A.
Published: May 2004

Thermally‐initiated living radical graft polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) with ozone‐pretreated poly[N,N′‐(1,4‐phenylene)‐3,3′,4,4′‐benzophenonetetra‐carboxylic amic acid] (PAmA) via a reversible addition–fragmentation chain‐transfer (RAFT)‐mediated process was carried out. The chemical compositions and structures of the copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and molecular weight measurements. The “living” character of the grafted PEGMA side chains was ascertained in the subsequent extension of the PEGMA side chains. Nanoporous low‐dielectric‐constant (low‐κ) polyimide (PI) films were prepared by thermal imidization of the PAmA graft copolymers under reduced argon pressure, followed by thermal decomposition of the side chains in air. The nanoporous PI films obtained from the RAFT‐mediated graft copolymers had well‐preserved PI backbones, porosity in the range of 5–17 %, and pore size in the range of 30–50 nm. The pores were smaller and the pore‐size distribution more uniform than those of the corresponding nanoporous PI films obtained via graft copolymers from conventional free‐radical processes. Dielectric constants approaching 2 were obtained for the nanoporous PI films prepared from the RAFT‐mediated graft copolymers.
Reversible Cluster Formation of Colloidal Nanospheres by Interparticle Photodimerization
Authors: Yuan X. , Fischer K. , Schärtl W.
Published: May 2004

Crosslinked spherical nanoparticles based on trimethoxysilane monomers have been prepared by polycondensation in aqueous emulsion. These particles have been labeled chemically at their surface region with two different types of organic dye molecules (cinnamate, coumarin), which both are well known for their ability to undergo a reversible photodimerization if irradiated with light of a suitable wavelength. Upon irradiation of dilute solutions of these nanoparticles with UV light, the photodimerization of labels belonging to different colloidal nanoparticles caused the formation of large colloidal clusters consisting of chemically bound individual nanospheres. This process has been quantitatively investigated using light scattering and atomic force microscopy. Importantly, utilizing the reversibility of the photoreaction, the clusters could be broken up by irradiation of the sample with UV light of shorter wavelengths than the light used for their formation
Solventless Polymerization to Grow Thin Films on Solid Substrates
Authors: Gu H. , Fu D. , Weng L.‐T. , Xie J. , Xu B.
Published: May 2004

We report on the formation of polymeric thin films on a solid surface using gaseous monomers. The process consists of adding catalysts on the surface of a solid substrate and polymerizing volatile monomers at the gas/solid interface, or directly using the vapors of the catalyst and the monomers to selectively form polymers inside the microchannels. The morphology and properties of these thin films depend on the concentration of catalysts, the time of exposure to the monomers, and the type of the monomers, which can be easily controlled at the molecular level. This solventless process can be used for a range of applications.
Light intensity distribution in a photocatalytic reactor using finite volume
Authors: Pareek Vishnu K. , Adesina Adesoji A.
Published: May 2004

A conservative variant of discrete ordinate model was used to solve the radiation transport equation. The model prediction was used to assess the effect of wall reflectivity, catalyst loading, and phase function parameter on the light intensity distribution in an annular heterogeneous photocatalytic reactor. For relatively low catalyst loadings, the wall reflectivity strongly influenced the light intensity distribution. However, for an optically thick medium, the wall reflectivity had very little or no effect. The volume‐average light intensity distribution decreased rather sharply with the catalyst loading and an opposite trend was obtained for the local volumetric rate of energy absorption (LVREA). However, after the initial sharp increase, the LVREA appeared independent of catalyst loading. For nonreflecting reactor walls, phase function parameter did not show much influence. However, for the specularly reflecting reactor walls and optically thin mediums, a moderate dependency on the phase function parameter was observed. 2004 American Institute of Chemical Engineers AIChE J, 50:1273–1288, 2004
Hybrid predictive control of process systems
Authors: Mhaskar Prashant , El‐Farra Nael H. , Christofides Panagiotis D.
Published: May 2004

The operation of chemical processes often requires respecting constraints on manipulated inputs and process states. Input constraints typically reflect limits on the capacity of control actuators, such as valves or pumps, whereas state constraints represent desirable ranges of operation for process variables, such as temperatures or concentrations. Constraints, however, limit the set of initial conditions, starting from where a process can be stabilized at a possibly open‐loop unstable steady state. Therefore, in control of constrained processes, it is important to obtain an explicit characterization of the region of closed‐loop stability. Model predictive control (MPC) provides a suitable framework for implementing control that respects manipulated input and process variable constraints while meeting prescribed performance objectives. Unfortunately, the implicit nature of the feedback law in MPC (the control action is computed by solving on‐line a constrained optimization problem at each sampling time) makes the a priori computation of the closed‐loop stability region a very difficult task. Such a computation, however, is possible when Lyapunov‐based bounded control techniques are used to design controllers for the stabilization of systems with manipulated input constraints. Motivated by this, the present work proposes a hybrid predictive control structure, which seamlessly unites MPC and bounded control, for output feedback stabilization of linear systems with input constraints. The design of the proposed structure is based on the idea of using a bounded controller, with its associated region of stability, as a “fallback” controller for the output feedback implementation of MPC. Switching laws are derived to orchestrate the transition between the two controllers in a way that reconciles their respective stability and optimality properties. The switched closed‐loop system is shown to possess a region of guaranteed stability, achieved by appropriately switching between the two controllers. The proposed hybrid control structure is shown to provide a safety net for the practical implementation of MPC by providing a priori knowledge, through off‐line computations, of a large set of initial conditions for which closed‐loop stability is guaranteed. Finally, two simulation studies are presented to demonstrate the implementation and evaluate the effectiveness of the proposed hybrid predictive control scheme, as well as test its robustness with respect to modeling errors and measurement noise. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1242–1259, 2004
Modeling the partial oxidation of methane in a fixed bed with detailed chemistry
Authors: Bizzi M. , Saracco G. , Schwiedernoch R. , Deutschmann O.
Published: May 2004

This work presents a model of a fixed‐bed reactor for the catalytic partial oxidation of methane to synthesis gas at short contact time. The transient model, one dimensional in space, accounts for separate energy equations for the gas and solid phases, interphase heat and mass transfer, internal radiation within the fixed bed, longitudinal gas‐phase dispersion, and detailed surface kinetics. The model is used to analyze the influence of the feedstock composition and temperature on the conversion and selectivity reactor performance. Furthermore, the study also investigates the blowout of the reaction and the impact of reactor geometry on the performance. Reactor scale‐up is discussed and a general criterion is formulated. © 2004 American Institute of Chemical Engineers AIChE J, 50:1289–1299, 2004
Phenotype and X inactivation in 45,X/46,X,r(X) cases
Authors: Leppig Kathleen A. , Sybert Virginia P. , Ross Judith L. , Cunniff Christopher , Trejo Tina , Raskind Wendy H. , Disteche Christine M.
Published: May 2004

We studied a new series of 21 individuals mosaic for a ring X chromosome [r(X)]. Of nine individuals with mental retardation, only one had a r(X) that lacked XIST (X‐inactive‐specific transcript) and was not subject to X inactivation, which would explain the abnormal phenotype; the remaining eight cases had XIST on their r(X). The majority of cases (five of seven) with mental retardation had an apparently early replicating r(X); but the androgen receptor gene (AR) was methylated on one allele in five of six informative cases, including two cases with an early replicating r(X). These conflicting results on two indicators of X inactivation suggest a potential dissociation between late replication and DNA methylation in these r(X) chromosomes, which may fail to become completely silenced. Of the twelve subjects who were not mentally retarded, all had XIST present on their r(X) and most (8/10) showed a late replicating r(X), together with AR methylation in all five informative cases, indicating r(X) inactivation. Thus, the unusual phenotypic features and mental retardation associated with the presence of a r(X) cannot be explained solely on the basis of presence or absence of XIST. The r(X) in cases with mental retardation were consistently smaller than those in individuals with normal intelligence, perhaps indicating inability for small rings to undergo structural changes associated with complete X inactivation or lethality in cases with a large non‐inactivated r(X). Of the Turner syndrome features present in the r(X) cases, only edema was present in a lesser frequency than in 45,X individuals. Our cases generally had a less severe phenotype than those previously reported, suggesting that reported incidences of abnormalities may be influenced by ascertainment bias, with mental retardation potentially unrelated to the presence of the r(X) in some cases. © 2004 Wiley‐Liss, Inc.
Forest use and activity patterns ofCallimico goeldiiin comparison to two sympatric tamarins,Saguinus fuscicollisandSaguinus labiatus
Authors: Porter Leila M.
Published: May 2004

Callimico goeldii,Saguinus fuscicollis, andS. labiatusare sympatric in northern Bolivia and differ from each other in patterns of spatial and structural use of their environment.C. goeldiihas a home range five times larger than that of mixed‐species troops ofS. fuscicollisandS. labiatus. The larger overlapping home range ofC. goeldiiallows it to move amongSaguinustroops, giving it access to a wide range of different microhabitats. All three species use the most common microhabitat in the area, primary forest with dense understory, more than any other microhabitat type.C. goeldiihabitat use varies by season, with bamboo andHeliconiamicrohabitats used more during the dry season. Each species shows preferences for different height classes:C. goeldiiis found almost exclusively in the understory,S. fuscicollisuses the understory and middle canopy, andS. labiatusis found mostly in the middle canopy. These height class preferences are reflected in each species' locomotor styles, withC. goeldiishowing the highest rates of vertical clinging and leaping, andS. labiatusshowing the highest rates of branch‐to‐branch leaping and quadrupedal movement. The results suggest thatC. goeldiimay be restricted to forests with dense understory and a mosaic of other microhabitats. Furthermore,C. goeldiidoes not appear to use its tegulae for large branch foraging, but rather for vertical clinging and leaping between small vertical supports. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.
Are adult physiques geometrically similar? The dangers of allometric scaling using body mass power laws
Authors: Nevill Alan M. , Stewart Arthur D. , Olds Tim , Holder Roger
Published: May 2004

Human physique classification by somatotype assumes that adult humans are geometric similar to each other. However, this assumption has yet to be adequately tested in athletic and nonexercising human populations. In this study, we assessed this assumption by comparing the mass exponents associated with girth measurements taken at 13 different sites throughout the body in 478 subjects (279 athletic subjects, and 199 nonexercising controls). Corrected girths which account for subcutaneous adipose tissue at the upper arm, thigh, and calf sites, and which simulate muscle circumference, were also calculated. If subjects are geometrically similar to each other, girth exponents should be approximately proportional to M1/3, where M is the subjects' body mass. This study confirms that human adult physiques are not geometrically similar to each other. In both athletic subjects and nonexercising controls, body circumferences/limb girths develop at a greater rate than that anticipated by geometric similarity in fleshy sites containing both muscle and fat (upper arms and legs), and less than anticipated in bony sites (head, wrists, and ankles). Interestingly, head girths appear to remain almost constant, irrespective of subjects' body size/mass. The results also suggest that thigh muscle girths of athletes and controls increase at a greater rate than that predicted by geometric similarity, proportional to body mass (M0.439 and M0.377, respectively). These systematic deviations from geometric similarity have serious implications for the allometric scaling of variables such as energy expenditure, oxygen uptake, anaerobic power, and thermodynamic or anthropometric studies involving individuals of differing size. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.
Synthesis of poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate) triblock copolymer by atom transfer radical polymerization
Authors: Zhu Xiulin , Gu Yurong , Chen Gaojian , Cheng Zhenping , Lu Jianmei
Published: May 2004

The synthesis of triblock copolymer poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate), using atom transfer radical polymerization (ATRP), is reported. The copolymers were prepared in two steps. First, polystyrene was synthesized by ATRP using α,α′‐dichloro‐p‐xylene/CuBr/bpy as the initiating system; Second, polystyrene was further used as macroinitiator for the ATRP of octadecyl acrylate to prepare ABA triblock copolymers in the presence of FeCl2·4H2O/PPh3 in toluene. Polymers with controlled molecular weight (Mn = 17,000–23,400) and low polydispersity index value (1.33–1.44) were obtained. The relationship between molecular weight versus conversion showed a straight line. The effect of reaction temperature on polymerization was also investigated, showing a faster polymerization rate under higher temperature. The copolymers were characterized by FTIR, 1H‐NMR, DSC, and GPC and the crystallization behavior of the copolymers was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1539–1545, 2004
Effect of diatomite/polyethylene glycol binary processing aids on the rheology of a metallocene linear low‐density polyethylene
Authors: Liu Xiaolong , Li Huilin
Published: May 2004

Flow performance of metallocene linear low‐density polyethylene (mLLDPE) containing small amounts of polyethylene glycol (PEG) diatomite and diatomite/PEG binary processing aids respectively was investigated. The mLLDPE melt viscosity is increased by the addition of diatomite, but is decreased by addition of PEG or the diatomite/PEG binary processing aids. It was also found that the viscosity reduction of mLLDPE with the addition of diatomite/PEG binary processing aid was significantly greater than that obtained with the addition of only PEG. The flow curves of mLLDPE containing diatomite/PEG binary processing aid show extremely lower value and stronger dependence on shear rate than the others. It is suggested that the rheological improvement of mLLDPE with diatomite/PEG binary processing aids resulted not entirely from the wall slip promoted by PEG; the intrinsic structure may have changed under the application of shear flow. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1546–1552, 2004
Matrix Reactivity of Al and Ga Atoms (M) in the Presence of Silane: Generation and Characterization of the η2‐Coordinated Complex M⋅SiH4, the Insertion Product HMSiH3, and the MISpecies MSiH3in a Solid Argon Matrix
Authors: Gaertner Benjamin , Himmel Hans‐Jörg , Macrae Victoria A. , Downs Anthony J. , Greene Tim M.
Published: May 2004

Matrix isolation experiments give evidence for the formation of the loosely bonded metal–silane complex M⋅SiH4by the spontaneous reaction of Al or Ga atoms (M) with silane in a solid Ar matrix at 12 K; however, Ga2appears to insert spontaneously into an SiH bond to form HGaGaSiH3, probably with the structure HGa(μ‐SiH3)Ga. In M⋅SiH4the metal atom is η2‐coordinated by the silane, resulting in a species withC2vsymmetry. The complex has a distinctive photochemistry: it can be converted on photolysis atλ≈410 or ≈254 nm to its tautomer, HMSiH3, which also has a doublet ground electronic state and from which it can be regenerated withλ≈580 nm radiation. Broadband UV‐visible photolysis (λ=200–800 nm) results in decomposition of HMSiH3, the univalent species MSiH3being the only detectable product. The experimental data collected for several silane isotopomers (SiH4, SiD4, and SiD3H) and different reagent concentrations, together with the results of sophisticated quantum chemical calculations, are used to explore in detail the properties of the detected species and the reaction pathways compassing their formation.
Tetrahedral Chalcogenide Clusters and Open Frameworks
Authors: Bu Xianhui , Zheng Nanfeng , Feng Pingyun
Published: May 2004

By integrating porosity with electrical or optical properties, microporous chalcogenides may have unique applications. Here we review recent advances and discuss concepts in the synthesis and crystal structure of tetrahedral clusters and their frameworks. These chalcogenides can be viewed as trivalent metal chalcogenides doped with tetra‐, di‐, or monovalent metal cations. Low‐valent cations help to increase the cluster size, while high‐valent cations have the opposite effect.
Self‐Assembly, Optical Behavior, and Permeability of a Novel Capsule Based on an Azo Dye and Polyelectrolytes
Authors: Tao Xia , Li Junbai , Möhwald Helmuth
Published: May 2004

A novel capsule composed of an azo dye, Congo red (CR), and different polymers, including poly(styrenesulfonate, sodium salt) (PSS), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA), have been successfully fabricated by the layer‐by‐layer self‐assembly technique. The stepwise linear deposition process was monitored by means of UV‐visible absorption measurements. The formation of hollow capsules was verified by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). The resulting hollow PSS/PAH/CR/PDDA capsules displayed a sensitive response to visible light. Optical changes of the hollow capsules prior to and after the photoreaction were investigated in detail by means of UV‐visible spectroscopy, CLSM, and SFM. It was found that the photochemical reaction of the assembled hollow capsules depends strongly on the matrix. Qualitative results on the permeability of the hollow capsule walls with CR as one component indicate that the permeability of the walls can be easily photo‐controlled at varying irradiation time intervals without addition of external chemicals.
Notch1 expression on T cells is not required for CD4+ T helper differentiation
Authors: Tacchini‐Cottier Fabienne , Allenbach Cindy , Otten Luc A. , Radtke Freddy
Published: May 2004

Notch1 proteins are involved in binary cell fate decisions. To determine the role of Notch1 in the differentiation of CD4+ Th1 versus Th2 cells, we have compared T helper polarization in vitro in naive CD4+ T cells isolated from mice in which the N1 gene is specifically inactivated in all mature T cells. Following activation, Notch1‐deficient CD4+ T cells transcribed and secreted IFN‐γ under Th1 conditions and IL‐4 under Th2 conditions at levels similar to that of control CD4+ T cells. These results show that Notch1 is dispensable for the development of Th1 and Th2 phenotypes in vitro. The requirement for Notch1 in Th1 differentiation in vivo was analyzed following inoculation of Leishmania major in mice with a T cell‐specific inactivation of the Notch1 gene. Following infection, these mice controlled parasite growth at the site of infection and healed their lesions. The mice developed a protective Th1 immune response characterized by high levels of IFN‐γ mRNA and protein and low levels of IL‐4 mRNA with no IL‐4 protein in their lymph node cells. Taken together, these results indicate that Notch1 is not critically involved in CD4+ T helper 1 differentiation and in resolution of lesions following infection with L. major.
Impaired migration of NOD mouse thymocytes: a fibronectin receptor‐related defect
Authors: Cotta‐de‐Almeida Vinícius , Villa‐Verde Déa Maria Serra , Lepault Françoise , Pléau Jean‐Marie , Dardenne Mireille , Savino Wilson
Published: May 2004

We previously showed intrathymic alterations in non‐obese diabetic (NOD) mice, including the appearance of giant perivascular spaces, filled with mature thymocytes, intermingled with an extracellular matrix network. This raised the hypothesis of a defect in thymocyte migration with partial arrest of exiting thymocytes in the perivascular spaces. Herein, we investigated the expression of receptors for fibronectin [very late antigen (VLA)‐4 and VLA‐5] and laminin (VLA‐6), known to play a role in thymocyte migration. When compared with two normal and one other autoimmune mouse strains, a decrease of VLA‐5 expression in NOD thymocytes was noticed, being firstly observed in late CD4/CD8 double‐negative cells, and more pronounced in mature CD4+ and CD8+ thymocytes. Functionally, thymocyte exit from the lymphoepithelial complexes, the thymic nurse cells, was reduced. Moreover, NOD thymocyte adhesion to thymic epithelial cells as well as to fibronectin was diminished, and so was the migration of NOD thymocytes through fibronectin‐containing transwell chambers. In situ, intra‐perivascular space thymocytes were VLA‐5‐negative, suggesting a correlation between the thymocyte arrest within these structures and loss of VLA‐5 expression. Overall, our data reveal impairment in NOD thymocyte migration, and correspond to the first demonstration of a functional fibronectin receptor defect in the immune system.
Small interference RNA modulation of IL‐10 in human monocyte‐derived dendritic cells enhances the Th1 response
Authors: Liu Gentao , Ng Hiushan , Akasaki Yasuharu , Yuan Xiangpeng , Ehtesham Moneeb , Yin Dong , Black Keith L. , Yu John S.
Published: May 2004

RNA interference technology has been used to modulate dendritic cell (DC) function by targeting the expression of genes such as IL‐12 and NF‐kB. In this paper, we demonstrate that transfectionof DC with IL‐10‐specific double strands of small interference RNA (siRNA) resulted in potent suppression of IL‐10 gene expression without inducing DC apoptosis or blocking DC maturation. Inhibition of IL‐10 by siRNA was accompanied by increased CD40 expression and IL‐12 production after maturation, which endowed DC with the ability to significantly enhance allogeneic T cell proliferation. IL‐10 siRNA transfection did not affect MHC class II, CD86, CD83, or CD54 expression in mature DC. To further test the ability of IL‐10 siRNA‐treated DC to induce a T cell response, naive CD4 T cells were stimulated by autologous DC pulsed with KLH. The results indicated that IL‐10 siRNA‐transfected DC enhanced Th1 responses by increasing IFN‐γ and decreasing IL‐4 production. These findings suggest the potential for a novel immunotherapeutic strategy of using IL‐10 siRNA‐transfected antigen‐presenting cells as vaccine delivery agents to boost the Th1 response against pathogens and tumors that are controlled by Th1 immunity.
Chemical Methods for Ether‐Bond Cleavage by Electron‐Transfer Reagents
Authors: Grobelny Zbigniew
Published: May 2004

Ethers can easily be cleaved with various electron‐transfer reagents. New data concerning the chemical methods of the regioselective opening of the ether bond with alkali metals (M0), alkali metal aromatic radical anions (Ar·−, M+), alkalides (M−, M+C; C denotes a ligand) and low‐valent transition‐metal compounds are presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Enhancement of pool boiling heat transfer in water and ethanol/water mixtures (effect of surface‐active agent)
Authors: Inoue Toshiaki , Teruya Yoshio , Ishii Masaru , Monde Masanori
Published: May 2004

The surface tension of alcohol/water mixtures has been measured over the whole fraction range and then it has been measured when a surface‐active agent was added into the mixtures. The effect of the concentration of alcohol and the surface‐ active agent on surface tension was experimentally clarified, in order to gain base data related to enhancement of the heat transfer coefficient in the mixtures and water. The experiment was also carried out to enhance the boiling heat transfer coefficients of water and alcohol/water mixtures on a horizontal heated fine wire at a pressure of 0.1 MPa by adding a surface‐active agent into the tested liquid. The results show, the coefficients were enhanced in lower alcohol concentration (C ≦ 0.5) and low heat flux range which occur just after the onset of boiling. It was also found that the enhancement effect by the surfactant disappears in concentrations over 1000 ppm. Finally, we demonstrated that the surface tension remarkably affects the heat transfer coefficients in nucleate pool boiling. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 229–244, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20010
Research on convective condensation heat transfer for a gas mixture in a vertical tube
Authors: Jia Li , Peng Xiaofeng
Published: May 2004

This paper discusses the convective condensation of a gas mixture in a vertical tube. A mathematical model was derived by combining a modified film model and Nusselt's condensation theory. The effect of wall temperature on film thickness and interfacial temperature was predicted and film thickness was calculated. When compared with the gas phase resistance method, the film model is better. The phenomenon of SO2 absorption into condensate is illustrated and discussed. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 219–228, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20011
Heat transfer enhancement by crossflow‐induced vibration
Authors: Tian Mao‐cheng , Cheng Lin , Lin Yi‐qing , Zhang Guan‐min
Published: May 2004

A new method of heat transfer enhancement by water crossflow‐induced vibration is presented. A heat transfer element which involves elastic tube bundles has been designed. This system has excellent response characteristics of vibration to the crossflow. A triangular pole device for producing pulsating flow was adopted. This device can induce vibration in a fixed range of frequencies and has a profound influence on heat transfer augmentation. For the constant heat flux boundary condition, experiments are carried out on the heat transfer characteristics of elastic tube bundles augmented by flow‐induced vibration in a water crossflow. Compared with static tube bundles, the out‐tube average convective heat transfer coefficients of the elastic tube bundles are increased by 100–150% under the condition of crossflow‐induced vibration. Dimensionless equations describing the outside heat transfer coefficient for the elastic tube bundles were acquired. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 211–218, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20012
A low‐temperature biomimetic calcium phosphate surface enhances early implant fixation in a rat model
Authors: Kuroda S. , Virdi A. S. , Li P. , Healy K. E. , Sumner D. R.
Published: May 2004

The present study demonstrates increased early mechanical fixation of titanium implants coated with a new biomimetic apatite surface in a rat model. Male Sprague‐Dawley rats received unilateral femoral medullary implants for periods of 1–4 weeks. The strength of fixation of the implant to the host bone increased more rapidly in the group receiving apatite‐treated implants compared with the control group as evidenced by the apatite group's 21‐fold greater fixation strength at 1 week (p = 0.009), 4‐fold greater fixation strength at 2 weeks (p = 0.041), and 2‐fold greater fixation strength at 4 weeks (p = 0.093) compared with the control. Fixation strength was correlated with bone–implant contact as determined from micro computed tomography assessment of the specimens (r2 = 0.338, p = 0.011 in the control group and r2 = 0.543, p < 0.001 in the apatite group). Furthermore, for a given amount of bone–implant contact, the fixation strength was higher in the apatite group than in the control group (p = 0.011), suggesting that the bone formed a stronger bond to the apatite coating than to the titanium. This difference in bonding strength accounted for the difference in mechanical behavior. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 66–73, 2004
Endothelial cell barrier regulation by sphingosine 1‐phosphate
Authors: McVerry Bryan J. , Garcia Joe G.N.
Published: May 2004

Disruption of vascular barrier integrity markedly increases permeability to fluid and solute and is the central pathophysiologic mechanism of many inflammatory disease processes, including sepsis and acute lung injury (ALI). Dynamic control of the endothelial barrier involves complex signaling to the endothelial cytoskeleton and to adhesion complexes between neighboring cells and between cells and the underlying matrix. Sphingosine 1‐phosphate (S1P), a biologically active lipid generated by hydrolysis of membrane lipids in activated platelets, organizes actin into a strong cortical ring and strengthens both intercellular and cell–matrix adherence. The mechanisms by which S1P increases endothelial barrier integrity remain the focus of intense basic research. The downstream structural changes induced by S1P interact to decrease vascular permeability to fluid and solute, which translates into a reduction lung edema formation in animal models of ALI, thus suggesting a potentially life‐saving therapeutic role for vascular barrier modulation in critically ill patients. © 2004 Wiley‐Liss, Inc.
Endoplasmic reticulum stress triggers an acute proteasome‐dependent degradation of ATF6
Authors: Hong Min , Li Mingqing , Mao Changhui , Lee Amy S.
Published: May 2004

ATF6, a 670 amino acid endoplasmic reticulum (ER) transmembrane glycoprotein with the electrophoretic mobility of a 90 kDa protein, is a key transcriptional activator of the unfolded protein response (UPR) that allows mammalian cells to maintain cellular homeostasis when the cells are subjected to a variety of environmental and physiological stress. Previous studies have established that ATF6 is a short‐lived protein, the activation of which involves relocation from the ER to the Golgi where it is cleaved by the S1P/S2P protease system to generate a nuclear form that acts as a transcriptional activator for ER‐stress inducible target genes such as Grp78/BiP. We report here that in addition to this process, ER‐stress mediated by thapsigargin triggers an acute proteasomal degradation of the pre‐existing pool of p90ATF6 independent of S1P/S2P cleavage. We showed that ATF6 is a direct target of proteasome‐ubiquitin pathway, and this process can be suppressed by proteasome inhibitors, ALLN and MG115. We further observed that in non‐stressed cells, p90ATF6 can be stabilized by MG115 but not ALLN and that treatment of cells with MG115 results in Grp78 induction in the absence of ER stress. These studies suggest that ER‐stress induced acute, transit degradation of p90ATF6 could represent a novel cellular defense mechanism to prevent premature cell death resulting from p90ATF6 activation. Further, inhibition of proteasome activity can result in chaperone protein gene induction through stabilization of p90ATF6 as well as accumulation of malfolded proteins. © 2004 Wiley‐Liss, Inc.
Gene expression profile of human bone marrow stromal cells determined by restriction fragment differential display analysis
Authors: Monticone Massimiliano , Liu Yi , Tonachini Laura , Mastrogiacomo Maddalena , Parodi Stefano , Quarto Rodolfo , Cancedda Ranieri , Castagnola Patrizio
Published: May 2004

Using an in vitro osteogenic culture system, we carried out a restriction fragment differential display (RFDD‐PCR) to identify genes expressed by these cells in their undifferentiated stage and not expressed, or expressed at a lower level, in a closely related but distinct cell type: bone marrow stromal cells (BMSC)‐derived osteoblasts (BDO). Forty‐seven candidate regulated genes, selected by RFDD, were analyzed by RT‐PCR analysis in three cell clones and in primary cultures from seven different donors. A subset of three genes were confirmed as upregulated in BMSC relative to BDO in every primary culture and cloned population examined: βIG‐h3, IGFbp3, and LOXL2. Their differential expression was confirmed by Northern analysis and the corresponding proteins were detected by immunolocalization in BMSC. © 2004 Wiley‐Liss, Inc.
Molecular circuits of apoptosis regulation and cell division control: The survivin paradigm
Authors: Altieri Dario C.
Published: May 2004

The coupling of cell proliferation to cell death is thought to function as a pivotal crossroad, essential to preserve normal homeostasis and to eliminate dangerous cells before they divide. Survivin is a prototype molecule at this crossroad, intercalated in protection against mitochondrial cell death and orchestrating various aspects of cell division. Dramatically exploited in cancer and an unfavorable gene signature for disease outcome, the survivin pathway has now provided tangible opportunities for targeted, rational cancer therapy. © 2004 Wiley‐Liss, Inc.
Accuracy of free energies of hydration using CM1 and CM3 atomic charges
Authors: Udier–Blagović Marina , Morales De Tirado Patricia , Pearlman Shoshannah A. , Jorgensen William L.
Published: May 2004

Absolute free energies of hydration (ΔGhyd) have been computed for 25 diverse organic molecules using partial atomic charges derived from AM1 and PM3 wave functions via the CM1 and CM3 procedures of Cramer, Truhlar, and coworkers. Comparisons are made with results using charges fit to the electrostatic potential surface (EPS) from ab initio 6‐31G* wave functions and from the OPLS‐AA force field. OPLS Lennard–Jones parameters for the organic molecules were used together with the TIP4P water model in Monte Carlo simulations with free energy perturbation theory. Absolute free energies of hydration were computed for OPLS united‐atom and all‐atom methane by annihilating the solutes in water and in the gas phase, and absolute ΔGhyd values for all other molecules were computed via transformation to one of these references. Optimal charge scaling factors were determined by minimizing the unsigned average error between experimental and calculated hydration free energies. The PM3‐based charge models do not lead to lower average errors than obtained with the EPS charges for the subset of 13 molecules in the original study. However, improvement is obtained by scaling the CM1A partial charges by 1.14 and the CM3A charges by 1.15, which leads to average errors of 1.0 and 1.1 kcal/mol for the full set of 25 molecules. The scaled CM1A charges also yield the best results for the hydration of amides including the E/Z free‐energy difference for N‐methylacetamide in water. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1322–1332, 2004
Determining sequences and post‐translational modifications of novel conotoxins in Conus victoriae using cDNA sequencing and mass spectrometry
Authors: Jakubowski Jennifer A. , Keays David A. , Kelley Wayne P. , Sandall David W. , Bingham Jon‐Paul , Livett Bruce G. , Gayler Ken R. , Sweedler Jonathan V.
Published: May 2004

A combination of cDNA cloning and detailed mass spectrometric analyses was employed to identify novel conotoxins from Conus victoriae. Eleven conotoxin sequences were determined using molecular methods: one belonging to the A superfamily (Vc1.1), six belonging to the O superfamily (Vc6.1–Vc6.6) and four members of the T superfamily (Vc5.1–Vc5.4). In order to verify the sequences and identify the post‐translational modifications (excluding the disulfide connectivity) of three Conus victoriae conotoxins, vc1a, vc5a and vc6a, deduced from sequences Vc1.1, Vc5.1, and Vc6.1, respectively, liquid chromatography/electrospray ionization ion trap mass spectrometry, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and nanospray ionization ion trap mass spectrometry with collisionally induced dissociation were performed on reduced and alkylated venom fractions. We report that vc1a, the native form of α‐conotoxin Vc1.1 (an unmodified 16 amino acid residue peptide that has notable pain‐relieving capabilities), includes a hydroxyproline and a γ‐carboxyglutamate residue. Conotoxin vc5a is a 10‐residue peptide with two disulfide bonds and a hydroxyproline and vc6a is a 25 amino acid peptide with three disulfide bonds. Copyright © 2004 John Wiley & Sons, Ltd.
Optimising flax production in the South Atlantic region of the USA
Authors: Foulk Jonn A , Akin Danny E , Dodd Roy B , Frederick James R
Published: May 2004

Worldwide the USA is the largest user of flax fibre, though very little is actually grown or produced in the USA. ‘Ariane’ flax was grown in 1990–1991, 1991–1992 and 1998–1999 in South Carolina, USA and evaluated for production characteristics. Plots (15 m long and 2 m wide) in the fall of 1990 and 1991 generated dry matter plant yields ranging from 4510 (early harvest at a seeding rate of 67 kg ha−1) to 7340 (late harvest at a seeding rate of 134 kg ha−1) kg ha−1. Based on these results, seed was sown on a private farm using a drill in 19 cm rows at a seeding rate of 101 kg ha−1 in 1998–1999. Early harvest, selected for optimal fibre quality, produced a dry matter plant yield that averaged 4076 kg ha−1. Late harvest, selected to optimise seed plus fibre, produced a dry matter plant yield that averaged 5076 kg ha−1. Stubble remaining in the field after mowing at about 6.0–7.6 cm above the soil surface resulted in a fibre loss of about 3% of total plant dry matter or 10% of potential total fibre yield. Dry matter and fibre yields suggested that flax could be produced in the southeastern USA using traditional farming methods for the area. Copyright © 2004 Society of Chemical Industry
Salvage of free flaps after venous thrombosis: Case report
Authors: Bonde Christian T. , Heslet Lars , Jansen Erik , Elberg Jens J.
Published: May 2004

Venous thrombosis of a free flap is a serious complication in microsurgery. Several agents with the ability to dissolve an occluding thrombus exist. Recombinant tissue plasminogen activator (rt‐PA) seems the most effective. We present our experience with a procedure that was successful in elimination of the occluding thrombus in two patients. © 2004 Wiley‐Liss, Inc.
Atraumatic suction tip for microsurgery: Technical note
Authors: Menovsky Tomas , De Vries Joost
Published: May 2004

During microneurosurgery, frequent suction is essential for a successful operative course. A new self‐made disposable suction tip is described which facilitates atraumatic suction, even near vital anatomical structures. The efficacy of this suction tip was confirmed in selected operative procedures. © 2004 Wiley‐Liss, Inc.
Inhibition of iNOS with 1400W improves contractile function and alters nos gene and protein expression in reperfused skeletal muscle
Authors: Patel Prerana , Qi Wen‐Ning , Allen Diane M. , Chen Long‐En , Seaber Anthony V. , Stamler Jonathan S. , Urbaniak James R.
Published: May 2004

This study examined the effects of 1400W, an inhibitor of inducible nitric oxide (iNOS), on contractile function and iNOS expression in reperfused skeletal muscle. The right extensor digitorum longus (EDL) muscle of 104 rats underwent a sham operation or 3‐h ischemia followed by 3‐h or 24‐h reperfusion (I/R). Rats received 3 mg/kg 1400W, 10 mg/kg 1400W, or water subcutaneously. Results showed that EDL contractile function in both 1400W‐treated groups significantly outperformed the controls at 24‐h but not at 3‐h reperfusion. Although iNOS expression increased in all three I/R groups during reperfusion, a significantly smaller increase was found in 1400W‐treated muscles after 3‐h reperfusion, and more dramatically so after 24‐h reperfusion. Our results indicate that inhibition of iNOS preserved the contractile function in reperfused skeletal muscle, perhaps via downregulating iNOS expression. Protection by 1400W at 24‐h reperfusion suggests that the role of iNOS in exaggerating reperfusion injury is more prominent in the later stages of injury. © 2004 Wiley‐Liss, Inc.
Simple and viable in vitro perfusion model for training microvascular anastomoses
Authors: Krishnan Kartik G. , Dramm Peter , Schackert Gabriele
Published: May 2004

In this report, we describe a novel in vitro perfused microvessel model for training microvascular anastomotic exercises. Arteries and veins with a diameter of ca. 1 mm were explanted from chicken wings. These vessels were cannulated at both ends and mounted on a platform. Preserved, expired whole blood obtained from the blood bank was continuously injected through the proximal catheter, using an automatic perfusor. This in vitro perfused microvessel model exactly simulated the viable small‐animal vessels. The setting is very simply and reliably repeated; the materials used are very cheap and universally available. There are no ethical questions involved. Vessels explanted from the human placenta or omentum may be used in a similar manner to gain the “feel” of functioning human microvascular tissue. But such materials are rarer and require the approval of ethical committees. © 2004 Wiley‐Liss, Inc.
A Crank‐Nicolson and ADI Galerkin method with quadrature for hyperbolic problems
Authors: Ganesh M. , Mustapha K.
Published: May 2004

We propose, analyze, and implement fully discrete two‐time level Crank‐Nicolson methods with quadrature for solving second‐order hyperbolic initial boundary value problems. Our algorithms include a practical version of the ADI scheme of Fernandes and Fairweather [SIAM J Numer Anal 28 (1991), 1265–1281] and also generalize the methods and analyzes of Baker [SIAM J Numer Anal 13 (1976), 564–576] and Baker and Dougalis [SIAM J Numer Anal 13 (1976), 577–598]. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005
Tumor size as a predictor of outcome in pediatric non‐metastatic osteosarcoma of the extremity
Authors: Kaste Sue C. , Liu T. , Billups C.A. , Daw N.C. , Pratt C.B. , Meyer W.H.
Published: May 2004

Background

Better predictors of outcome would allow improved risk‐adapted therapy for pediatric nonmetastatic osteosarcoma of the extremity. We investigated the predictive value of MR imaging‐based measures of absolute and relative tumor size and volume at the time of diagnosis. We also assessed the relation of tumor size to age and histologic response.

Methods

We retrospectively abstracted demographic, treatment history, and outcome information of patients treated on a single institutional protocol. A single pediatric oncologic radiologist manually measured each primary lesion and the affected native bone in three dimensions on MR images obtained at the time of diagnosis. Eight parameters of tumor size were analyzed for their value in predicting overall survival (OS) and event‐free survival (EFS).

Results

The median age of the 42 patients was 13.5 years (range: 5.9–18.7 years); 50% were female and 74% were Caucasian. Absolute tumor volume was an important predictor of OS (P < 0.05); absolute tumor depth (analyzed as a continuous variable) was a significant predictor of OS (P = 0.018) and EFS (P = 0.036). Relative measures of tumor size were not found to predict outcome. No relation was seen between tumor size and histologic response.

Conclusions

Absolute tumor size at the time of diagnosis is significantly predictive of OS and EFS. If validated in a larger study, this indicator should be used in the design of risk‐adapted treatment protocols for osteosarcoma. © 2004 Wiley‐Liss, Inc.
Pharmacoepidemiology 101: data monitoring committees in the post‐marketing approval setting
Authors: Lilienfeld David E.
Published: May 2004

The development of the risk management paradigm for the enhancement of post‐marketing approval drug safety carries with it the need for external monitoring of the different approaches used by the sponsor. The concept of a Data Monitoring Committee (DMC), widely used in the management of randomized clinical trials, is adapted to provide this monitoring function. The rationale for the post‐marketing approval DMC is considered in the context of the risk management paradigm, as well as in the more traditional post‐marketing approval surveillance setting. The composition and operation of the post‐marketing approval DMC are considered, as well as the process of implementing the committee. Although the adaptation proposed in this article is focused on the paradigm proposed by the United States Food and Drug Administration, it is likely that it will require modification as risk management is adopted (and adapted) by other health regulators. Copyright © 2003 John Wiley & Sons, Ltd.
Polyisobutylene‐based biomaterials
Authors: Puskas Judit E. , Chen Yaohong , Dahman Yaser , Padavan Donna
Published: May 2004

This article highlights the biomaterial‐related research of the Macromolecular Engineering Research Centre (MERC). The MERC group concentrated on polyisobutylene (PIB)‐based biomaterials. In this article, first the unique properties of PIB are discussed, followed by a review of PIB‐based potential biomaterials. MERC's systematic research program aimed to develop novel PIB‐based biomaterials is then highlighted, including surface modification and biocompatibility studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3091–3109, 2004
Conformational changes of poly(ethylene oxide) in poly(ethylene oxide)/poly(methyl methacrylate) blends by supercritical carbon dioxide
Authors: Shieh Yeong‐Tarng , Liu Kuan‐Han
Published: May 2004

The effects of supercritical carbon dioxide (SC CO2) fluids on the morphology and/or conformation of poly(ethylene oxide) (PEO) in PEO/poly(methyl methacrylate) (PMMA) blends were investigated by means of differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and Fourier transform infrared (FTIR). According to DSC data for a given blend, the melting enthalpy and, therefore, degree of crystallinity of PEO were increased, whereas the melting temperature of PEO was decreased, with SC CO2 treatment. The enhancement of PEO crystallization with SC CO2 treatment, as demonstrated by DSC data, was supported by WAXD data. According to FTIR quantitative analyses, before SC CO2 treatments, the conformation of PEO was transformed from helix to trans planar zigzag via blending with PMMA. This helix‐to‐trans transformation of PEO increased proportionally with increasing PMMA content, with around 0.7% helix‐to‐trans transformation per 1% PMMA incorporation into the blend. For a given blend upon SC CO2 treatments, the conformation of PEO was transformed from trans to helix. This trans‐to‐helix transformation of PEO decreased with increasing PMMA contents in the blends because of the presence of interactions between the two polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2479–2489, 2004