bluuebunny/crossref_metadata_2025 huggingface dataset:
Fault detection and isolation for dynamic processes using recursive principal component analysis (PCA) based on filtering of signals
Authors: Jeng Jyh‐Cheng , Li Cheng‐Chih , Huang Hsiao‐Ping
Published: October 2007

A systematic procedure for the fault detection and isolation of dynamic systems is presented. The inputs of the process first pass through the dynamic filters which represent the process dynamics. Then, principal component analysis (PCA) is applied to the data matrix consisting of these filtered signals and the process outputs for fault detection. In case of a fault being detected, owing to an artificial linear relationship existing in the data matrix, the last principal component (LPC) is adopted for fault isolation. A recursive algorithm for PCA based on rank‐one matrix update of the covariance is derived to compute the LPC on line. Patterns of the LPC are devised to isolate these faults, which include constant‐bias and high‐frequency noises originating from sensor measurement, errors resulting from input disturbance and change in the process gain. Furthermore, the magnitude of the fault can also be identified from the computed LPC. An illustrative example is used to verify the effectiveness of the proposed method. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Delay‐compensated controllers for two‐input/two‐output (TITO) multivariable processes
Authors: Seshagiri Rao A. , Rao V. S. R. , Chidambaram M.
Published: October 2007

A decentralized controller design based on the direct synthesis method for two‐input/two‐output (TITO) processes in the Smith predictor configuration is proposed. The decentralized controllers are designed individually on the basis of the diagonal individual transfer functions of the process. Using the direct synthesis principle, the two decentralized controllers are designed using the individual diagonal transfer functions of the process matrix and the individual desired diagonal closed‐loop transfer functions. Further, these direct synthesis controllers are implemented in the Smith predictor configuration for each output. While converting from the synthesis controller to the Smith predictor configuration, the decentralized controller parameters are directly obtained in terms of the individual closed‐loop desired tuning parameters. The method is compared with the recently reported methods. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Disturbance observer design for continuous systems with delay
Authors: Jones R. W. , Tham M. T.
Published: October 2007

Disturbance observers (DOs), which are popularly used for improving the disturbance rejection capability of mechatronic servo control systems, offer several attractive features that could prove beneficial for process control systems. The tuning is simple and intuitive and they allow independent tuning of disturbance rejection characteristics, which is particularly helpful in situations in which gains need to be tuned on‐line. This paper is concerned with examining DO design for continuous‐time systems with delay. Two methods for incorporating time delay into traditional DO design are considered, to assess their relative performance, stability, and noise rejection characteristics. The performance of one of these time‐delay‐based DO approaches is then compared with proportional, integral and derivative (PID) control, designed using a maximum sensitivity approach, on a representative process model. The paper concludes by briefly examining the incorporation of a DO into a two‐degrees‐of‐freedom (2DOF) control structure. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.
Transitions and relaxations of copolypropylene molecules in copolypropylene–clay composites
Authors: Zhong Weixia , Qiao Xiuying , Cao Ming , Sun Kang , Zhang Guoding
Published: October 2007

Three commercial organoclays pretreated with C18H37N+H3, C18H37N+(CH3)3 and (C18H37)2N+(CH3)2, were used to prepare a series of copolypropylene (cPP)‐clay nancomposites by melt blending. Then, the effects of the clay content and pretreatment history on the transition and relaxation of cPP molecules in different composites were investigated in detail by dynamic mechanical analysis. The results show that the α‐relaxation, ascribed to the movement of polymer main chains within the crystalline regions of different cPP composites, is activated by the increase of clay content. The main β‐relaxation, assigned to the glass‐rubber transition of cPP segments in amorphous portions, is greatly limited by about 3–5 wt % clay loading, whereas drastically motivated with 7 wt % clay loading, which correlates closely with the dispersion order of clay layers in different composites. Lastly, the γ‐relaxation, associated with the motion of ethylene sequence of cPP chains, is restricted because of the increasing clay content. Additionally, it is found that the miscibility between cPP molecules and organoclay layers was strengthened as the clay premodifier varied from C18H37N+H3 to C18H37N+(CH3)3, but somewhat weakened when the premodifier changed as (C18H37)2N+(CH3)2. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Macromolecular assemblies of segmented poly(ester urethane)s and poly(ether urethane)s
Authors: Ioan Silvia , Lupu Mihaela , Epure Virginia , Ioanid Aurelia , Macocinschi Doina
Published: October 2007

Polyurethanes containing different soft and hard segments were investigated by fluorescence and scanning electron microscopy. The polarity dependence of the vibrational structure of the pyrene emission spectrum indicated the formation of aggregates at concentrations, which are significantly below the critical concentrations, which define the separation of dilute‐semidilute domains. Unlike the samples with 4,4′‐methylene diphenylene diisocyanate, the samples with 2,4‐tolylene diisocyanate in hard segments give the fluorescence spectra in which the pyrene excimer appears. The supermolecular structures associated with the form of spherulites or of spherical micelles were detected by scanning electron microscopy. The results were compared with previous reports concerning viscometric data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mechanical properties of crosslinked polyurethane elastomers based on well‐defined prepolymers
Authors: Król Piotr , Pilch‐Pitera Barbara
Published: October 2007

This article presents research findings for selected mechanical properties of polyurethane elastomers. The studied elastomers were synthesized with the prepolymer‐based method with the use of controlled molecular weight distribution (MWD) urethane oligomers and with the classical single‐stage method. Prepolymers with defined MWDs were obtained with the use of a multistage method, that is, step‐by‐step polyaddition. To produce elastomers, isocyanate oligomers were then crosslinked with triethanolamine, whereas hydroxyl oligomers were crosslinked with 4,4′,4′′‐triphenylmethane triisocyanate (Desmodur RE). The tensile strength of the obtained elastomers ranged from 1.0 to 7.0 MPa, the ultimate elongation approached 1700%, the Shore A hardness varied from 40 to 93°, and the abrasion resistance index fell within 15–140. The effects of the types of raw materials used, the chemical structures, the production methods, and the supermolecular structures on the mechanical properties of the obtained polyurethane elastomers were examined. When the obtained findings were generalized, it was concluded that the structural changes in the polyurethanes, which were favorable for intermolecular interactions, improved the tensile strength, hardness, and abrasion resistance of the materials and impaired their ultimate elongation at the same time. More orderly supermolecular structures and, therefore, superior mechanical properties were found for polyurethane elastomers produced with the prepolymer method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of olive residue benzylation on the thermal and mechanical properties of poly(vinyl chloride)/olive residue composites
Authors: Djidjelli H. , Boukerrou A. , Rabouhi A. , Founas R. , Kaci M. , Zefouni O. , Djillali N. , Belmouhoub L.
Published: October 2007

The changes in mechanical properties, the thermal stability, and the water absorption capacity of poly (vinyl chloride)/olive residue flour composites were studied as a function of various residue olive flour ratios, i.e., 0, 5, 15, and 25% by weight taking into account the effect of benzylation chemical treatment of the filler. The study showed that composite samples prepared with the untreated filler exhibited higher tensile modulus and hardness compared with the neat resin, whereas elongation and tensile strength were observed to decline. On the other hand, the PVC hardness was found to increase with addition of the untreated olive residue flour (ORF), however the composite samples prepared with the benzylated flour exhibited lower hardness than those prepared with untreated olive residue. Moreover, the amount of absorbed water depends on the amount of filler in the composite. The comparison of the results obtained from the samples of F5, F20, and F30 formulations between the untreated and treated ORF indicated a reduction in absorbed water for the composite samples containing treated ORF with benzyl chloride. As a result, the mechanical properties of the treated composites were improved. Furthermore, the thermal characterization of the different samples carried out by color change test and thermogravimetric analysis revealed an increase in the onset temperatures of decomposition for the treated composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Curing kinetics study of an epoxy resin system for T800 carbon fiber filament wound composites by dynamic and isothermal DSC
Authors: Chen Weiming , Li Peng , Yu Yunhua , Yang Xiaoping
Published: October 2007

Curing kinetics of DGEAC/DDM/DETDA/DGEB epoxy resin system was studied using dynamic and isothermal differential scanning calorimetry (DSC) for the preparation of T800 carbon fiber filament wound composites. In dynamic experiment, four kinds of epoxy resin systems were studied. Curing characteristics, such as curing range and curing temperatures of the epoxy resin system with mixed hardeners (DGEAC/DDM/DETDA), were found lying within those of the two epoxy resin systems with a single hardener (DGEAC/DDM, DGEAC/DETDA). The addition of reactive diluter (DGEB) caused increase in curing range and exothermic heat. In addition, the activation energies calculated by the isoconversional method of all four resin systems decreased to the minimum value in the early stage due to the autocatalytic role of hydroxyl groups in the curing reaction and then increased due to the increased viscosity and crosslink of epoxy systems. The addition of reactive diluter led to the decrease in activation energies on the initial stage (conversion = 0.1–0.3). In isothermal experiment, a series of isothermal DSC runs provided information about the curing kinetics of the DGEAC/DDM/DETDA/DGEB system over a wide temperature range. The results showed that the isothermal kinetic reaction of the epoxy resin followed an autocatalytic kinetic mechanism. The autocatalytic kinetic expression chosen in this work was suitable to analyze the curing kinetics of this system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmas
Authors: Wang Chunxia , Zhu Lu , Qiu Yiping
Published: October 2007

The effect of atmospheric pressure plasma treatment on wettability and dyeability of nylon 6 fibers is investigated. The plasma treatments resulted in an average of 10°–20° decrease in the advancing contact angle and 20°–30° decrease in the receding contact angle. An increased dye diffusion rate of nylon 6 fibers was observed using laser scanning confocal microscope (LSCM). Scanning electron microscope confirmed that the fiber surfaces were roughened, and X‐ray photoelectron spectroscopy showed that the polar groups on the fiber surfaces increased after the plasma treatments. As the plasma treatment time increased, a greater degree of etching was achieved and more polar groups such as hydroxyl and carboxyl groups produced on the surfaces of the nylon 6 fibers, leading to a better wettability and thus a better dyeability of the fiber. This study proved that LSCM may be effectively used in detecting the change of dye diffusion rate in nylon fibers treated with plasmas and the mounting medium should have a close refractive index as the fiber to avoid distortion of the fiber cross section image. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of the different rigidity of the chiral crosslinker on phase behaviors of side‐chain chiral liquid crystalline elastomers
Authors: Zhang Bao‐Yan , He Xiao‐Zhi , Liao Qing‐Feng , Zhou Qun‐Hua
Published: October 2007

In the present work, the phase behaviors of two series of side‐chain liquid crystalline elastomers (PI and PII series) derived from the same nematic liquid crystalline monomer and the different rigidity of chiral bisolefinic crosslinking units have been compared and studied extensively, and the effect of the different rigidity of crosslinker on the phase behavior of elastomers has been discussed. The chemical structure of the monomers and polymers obtained were confirmed by FTIR and 1H NMR spectroscopy. The phase behaviors were investigated by differential scanning calorimetry, polarizing optical microscopy measurement, thermogravimetric analyses, and X‐ray diffraction measurement. The two series of elastomers showed smectic or cholesteric phases. When the amount of different crosslinking units was less than 15 mol %, both of the elastomers displayed elasticity, reversible phase transition with wide mesophase temperature ranges, and high thermal stability. It is shown that the isotropization temperature values of PII series are higher than those of PI series, and the glass transition temperature values of PII series varied smoothly and that of PI series changed smoothly first and then abruptly with increasing the contents of crosslinkers with different rigidity. In addition, PI series showed an interesting change in LC texture near clearing point, but PII series did not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Superabsorbent hydrogel composed of covalently crosslinked gum arabic with fast swelling dynamics
Authors: Favaro Silvia L. , de Oliveira Fernando , Reis Adriano V. , Guilherme Marcos R. , Muniz Edvani C. , Tambourgi Elias B.
Published: October 2007

A superabsorbent hydrogel (SH) with fast swelling dynamics and good mechanical stability in the swollen state was prepared. The SH was obtained from chemically modified gum arabic (MGA) with glycidyl methacrylate (GMA), acrylic acid (AAc), and acrylamide (AAm). The water‐transport mechanisms and equilibrium swelling ratio (SR) were the parameters used to describe the water‐absorption profile of SH. A 23 factorial design with a central point was built to evaluate the influence of the chemical modification of gum arabic (GA) on the SH sensitivity to water. The main effects of the temperature and amount of GMA and the interaction effect of the temperature and amount of GMA on the SR responses were statistically significant. It was demonstrated that the amount of GMA had a more prominent effect on gel swelling. Lower elastic modulus values for the SH were found when a decreased amount of GMA was used (0.05 g), which produced an SH with a high SR capacity. The SH matrix consisting of 3.0 g of AAc, 0.5 g of AAm, and 0.5 g of MGA was more suitable to absorb a large amount of water (SR = 503.17 ± 22.65 within 60 min of water immersion) without its mechanical stability being affected. Better GA modifying conditions to produce such an SH were as follows: 60°C for the temperature, 24 h for the time of MGA, and 0.05 g for the amount of GMA. It exhibited a diffusional exponent higher than 0.89, which corresponded to the supercase II type of penetrating transport mechanism, indicating that its water‐absorption mechanism exclusively depended on the macromolecular relaxation of the polymer chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of maleic anhydride grafted polypropylene on the mechanical and morphological properties of chemically modified short‐pineapple‐leaf‐fiber‐reinforced polypropylene composites
Authors: Hujuri Ujwala , Chattopadhay Sanjay K. , Uppaluri Ramagopal , Ghoshal Aloke K.
Published: October 2007

With the rising cost of petroleum‐based fibers, the utilization of plant fibers in the manufacture of polymer–matrix composites is gaining importance worldwide. The scope of this study was to examine the perspective of the use of pineapple leaf fibers (PALFs) as reinforcements for polypropylene (PP). These fibers are environmentally friendly, low‐cost byproducts of pineapple cultivation and are readily available in the northeastern region of India. Here, both untreated and treated pineapple fibers were used. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizing agent. The polymer matrix of PP was used to prepare composite specimens with different volume fractions (5–20%) of fibers by the addition of 5% of MA‐g‐PP. These specimens were tested for their mechanical properties, and additional assessments were made via observations by scanning electron microscopy, thermogravimetric analysis, and IR spectroscopy. Increase in the impact behavior, flexural properties, and tensile moduli of the composites were noticed, and these were more appreciable in the treated fibers mixed with MA‐g‐PP. PALF in 10 vol % in PP mixed with MA‐g‐PP was the optimum and recommended composition, where the flexural properties were the maximum. The impact strength and the tensile modulus were also considerably high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Dynamic photorheological analysis of photopolymerizable urethane dimethacrylate resins with varying diluent content and light fluence
Authors: Piguet‐Ruinet F. , Love B. J.
Published: October 2007

The in situ measurement of dynamic changes in viscosity induced by illumination has been performed on a range of photosensitive urethane dimethacrylates (UDMA) evaluating the response at three different illuminations intensities (1, 2, and 5 W cm−2) and at three different diluent concentrations (15, 30, and 50%), using 1,6‐hexanediol dimethacrylate (HDDMA). The initial viscosity value ranged between 1 and 10 Pa s for the mixtures with final viscosities approaching 1 × 107 Pa s after illumination. The initial rise in viscosity was analyzed using an exponential model with an exponent ranging from 1.0 to 2.5 with time under exposure. Higher conversion rates were observed with both higher intensity and lower HDDMA content. The analytical approach taken here could aid in developing more sophisticated models that consider simultaneous flow and cure advancement in other thermosets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Fabrication of superhydrophobic silica‐based surfaces with high transmittance by using polypropylene and tetraeyhoxysilane precursors
Authors: Chang Kuei‐Chien , Chen Yu‐Kai , Chen Hui
Published: October 2007

Preparation of superhydrophobic silica‐based surfaces via sol–gel process by adding polyethylene glycol (PEG) polymer into the precursor solution has been developed. Surface roughness of the films was obtained by removing the organic polymer at 500°C and then the hydrophobic groups bonded onto the films were obtained by self‐assembly modification with a monolayer. Characteristic properties of the as‐prepared films were analyzed by contact angle measurements, scanning electron microscopy, atomic force microscopy, UV–vis scanning spectrophotometer, and X‐ray photoelectron spectrophotometer. The experimental parameters were varied by the type of silane species, the R ratio, the hydrolysis time of the precursor solution, the molecular weight of PEG, the pH value of mixing solution, and the different reagents for modification. The results showed that optimum ratio of TEOS/H2O/ethanol in the sol–gel process for precursor solution was set to 1/10/4. The better contact angles of the films can be obtained by the acid catalyst reaction, especially the pH value of mixing solution was adjusted to 0. When the as‐prepared rough films were modified with (tridecafluoro‐1,1,2,2‐tetrahydrooctyl) dimethylchlorosilane (TFCS), the contact angle of the film can be promoted to 150.4°, and the transmittance of the films in the visible light region was greater than 94.5%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Properties of diallyl phthalate resin modified with phthalic allyl ester having a hydroxyl group
Authors: Ohtsuka Keiko , Matsumoto Akihiro , Kimura Hajime
Published: October 2007

A phthalic allyl ester having a hydroxyl group [2‐(2‐hydroxy‐3‐allyloxypropanocarbonyl)‐allylphthalate (HDAP)] was synthesized by the reaction of phthalic monoallyl ester with allyl glycidyl ether. HDAP was added to a diallyl phthalate resin to a concentration of 30 wt % to improve the adhesive properties. These blends were cured with dicumyl peroxide. The lap shear strength of joints was measured to evaluate the adhesive properties of the modified diallyl phthalate resin to steel and copper. The lap shear strength of the diallyl phthalate resin was increased by modification with HDAP. By modification with HDAP, the lap shear strength to steel increased up to about 2.5 times that of the diallyl phthalate resin. Moreover, the lap shear strength to copper was about 3.0 times larger than that of the diallyl phthalate resin upon the addition of 30 wt % HDAP. These results suggested that the secondary hydroxyl group of HDAP (used as a modifier) formed a hydrogen bond to a hydroxyl group of water existing on the metal surface, and as a result, the adhesive strength to metals such as steel and copper increased. The thermal decomposition temperature of the modified diallyl phthalate resin was almost the same as that of the diallyl phthalate resin; on the other hand, the glass‐transition temperature of the modified diallyl phthalate resin decreased with an increasing concentration of HDAP. The electrical properties of the modified diallyl phthalate resin were almost the same as those of the diallyl phthalate resin. On the other hand, water absorption after boiling increased with an increasing concentration of HDAP. This result led to the conclusion that the secondary hydroxyl group of HDAP (used as a modifier) formed a hydrogen bond to water. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Enantioselective Tsuji Allylations
Authors: Mohr Justin T. , Stoltz Brian M.
Published: October 2007

The family of allylation reactions developed by Tsuji in the 1980s are capable of generating tertiary and quaternary carbon stereocenters from several synthetic precursors. Despite the utility of these transformations, they have seen little use in the synthesis of natural products. Recently, the power of these reactions was significantly enhanced by the development of enantioselective versions of these transformations. Applications of these methods to the enantioselective syntheses of natural products and pharmaceutical compounds highlight the importance of these developments.
Influence of information about specific absorption rate (SAR) upon customers' purchase decisions and safety evaluation of mobile phones
Authors: Wiedemann Peter M. , Schütz Holger , Clauberg Martin
Published: October 2007

This study investigated whether the SAR value is a purchase‐relevant characteristic of mobile phones for laypersons and what effect the disclosure of a precautionary SAR value has on laypersons' risk perception. The study consisted of two parts: Study part 1 used a conjoint analysis design to explore the relevance of the SAR value and other features of mobile phones for an intended buying decision. Study part 2 used an experimental, repeated measures design to examine the effect of the magnitude of SAR values and the disclosure of a precautionary SAR value on risk perception. In addition, the study included an analysis of prior concerns of the study participants with regard to mobile phone risks. Part 1 indicates that the SAR value has a high relevance for laypersons' purchase intentions. In the experimental purchase setting it ranks even before price and equipment features. The results of study part 2 show that providing information of a precautionary limit value does not influence risk perception. This result suggests that laypersons' underlying subjective “safety model” for mobile phones resembles more a “margin of safety” concept than a threshold concept. The latter observation holds true no matter how concerned the participants are. Bioelectromagnetics 29:133–144, 2008. © 2007 Wiley‐Liss, Inc.
Adaptive immunity in invertebrates: A straw house without a mechanistic foundation
Authors: Hauton Chris , Smith Valerie J.
Published: October 2007

Recently claims have been made for radical new insights in the field of invertebrate immunology that involve memory, specificity and/or maternal transfer of immunocompetence. For evidence these claims rely on phenomena, such as survival or reproductive capacity, observed at the level of the whole organism. The allure of these apparently revelatory hypotheses is that they are contrary to established views of innate immunity. They draw implicit analogy to adaptive responses in jawed vertebrates and the terminology used creates an incomplete and misleading picture. We argue that the case for adaptive immunity in invertebrates based only on such phenomena is weak and flawed, as it can only be upheld if supported by descriptions of the underlying mechanisms. We caution against a reliance on this approach as a means of advancing this field—highlighting, as an example, some negative commercial implications of adopting this approach. BioEssays 29:1138–1146, 2007. © 2007 Wiley Periodicals, Inc.
Transcriptional auxin–brassinosteroid crosstalk: Who's talking?
Authors: Hardtke Christian S.
Published: October 2007

The plant hormones auxin and brassinosteroid are both essential regulators of plant growth and known to influence both cell division and cell elongation in various developmental contexts. These physiological effects of auxin and brassinosteroid have been known for many years. Based on observations from external simultaneous application of both hormones to plant tissues, it has been suggested that they act in an interdependent and possibly synergistic manner. Recent work in the model plant Arabidopsis thaliana suggests that, at the molecular level, auxin–brassinosteroid synergism manifests itself in the regulation of the expression of common target genes. However, whether this reflects genuine hormone pathway‐dependent crosstalk modulation of the transcription machinery or rather indirect effects of hormone action on other cellular activities, such as hormone biosynthesis or the polar transport of auxin, is not entirely clear. This article reviews the evidence for transcriptional crosstalk between auxin and brassinosteroid and its molecular basis. BioEssays 29:1115–1123, 2007. © 2007 Wiley Periodicals, Inc.
Mitochondria and peroxisomes: Are the ‘Big Brother’ and the ‘Little Sister’ closer than assumed?
Authors: Schrader Michael , Yoon Yisang
Published: October 2007

Mitochondria and peroxisomes are essential subcellular organelles in mammals. Despite obvious differences, both organelles display certain morphological and functional similarities. Recent studies have elucidated that these highly dynamic and plastic organelles share components of their division machinery. Mitochondria and peroxisomes are metabolically linked organelles, which are cooperating and cross‐talking. This review addresses the dynamics and division of mitochondria and peroxisomes as well as their functional similarities to provide insight as to why these organelles share the fission machinery in evolutionary aspects.© 2007 Wiley Periodicals, Inc.
Greased hedgehogs: New links between hedgehog signaling and cholesterol metabolism
Authors: Breitling Rainer
Published: October 2007

The close link between signaling by the developmental regulators of the Hedgehog family and cholesterol biochemistry has been known for some time. The morphogen is covalently attached to cholesterol in a peculiar autocatalytic reaction and embryonal disruption of cholesterol synthesis leads to malformations that mimic Hh signaling defects. Recently, it was furthermore shown that secreted Hh could hitchhike on lipoprotein particles to establish its morphogenic gradient in the developing embryo. Additionally, there is new evidence that the Hh‐receptor Patched transmits the Hh signal by modulating the secretion of an inhibitory sterol molecule from the receiving cells. Here we present some of the most recent discoveries on the Hh–sterol link and discuss their implications from a systems design perspective. We predict that a robust functioning of the Hh pathway will require the involvement of more sterol metabolites, and these should be the subject of future research. BioEssays 29:1085–1094, 2007. © 2007 Wiley Periodicals, Inc.
Biotechnology of flavonoids and other phenylpropanoid‐derived natural products. Part I: Chemical diversity, impacts on plant biology and human health
Authors: Ververidis Filippos , Trantas Emmanouil , Douglas Carl , Vollmer Guenter , Kretzschmar Georg , Panopoulos Nickolas
Published: October 2007

Plant natural products derived from phenylalanine and the phenylpropanoid pathway are impressive in their chemical diversity and are the result of plant evolution, which has selected for the acquisition of large repertoires of pigments, structural and defensive compounds, all derived from a phenylpropanoid backboneviathe plant‐specific phenylpropanoid pathway. These compounds are important in plant growth, development and responses to environmental stresses and thus can have large impacts on agricultural productivity. While plant‐based medicines containing phenylpropanoid‐derived active components have long been used by humans, the benefits of specific flavonoids and other phenylpropanoid‐derived compounds to human health and their potential for long‐term health benefits have been only recognized more recently. In this part of the review, we discuss the diversity and biosynthetic origins of phenylpropanoids and particularly of the flavonoid and stilbenoid natural products. We then review data pertaining to the modes of action and biological properties of these compounds, referring on their effects on human health and physiology and their roles as plant defense and antimicrobial compounds. This review continues in Part II discussing the use of biotechnological tools targeting the rational reconstruction of multienzyme pathways in order to modify the production of such compounds in plants and model microbial systems for the benefit of agriculture and forestry.
Algorithms for the surgical management of retrorectal tumours
Authors: Woodfield J C , Chalmers A G , Phillips N , Sagar P M
Published: October 2007

Background

Retrorectal tumours are uncommon and may present a surgical challenge. The aim of this study was to identify a surgical strategy based on information gained from the multidisciplinary management of retrorectal tumours.

Methods

This was a retrospective review of 27 patients who had resection of retrorectal tumours between 1998 and 2006.

Results

The tumours included ten cystic lesions, two mature teratomas, four chordomas, seven neurogenic tumours, two sarcomas, one angiomyxoma and one gastrointestinal stromal tumour. The diagnosis was suggested initially by non-specific clinical presentation and palpation of a retrorectal mass on examination (16 patients), pelvic imaging (six), obstructed labour (one), recurrent pilonidal sinus (one), recurrent perianal sepsis (one) and return of symptoms after resection (two). Magnetic resonance imaging (MRI) confirmed the diagnosis and enabled surgical planning. The operative approach was perineal (12 patients), abdominal (11) or combined (four). Factors that influenced the operative approach were tumour position, its neoplastic nature, involvement of the pelvic sidewall or pelvic viscera, and size. The retrorectal tumour recurred in three patients.

Conclusion

A successful multidisciplinary surgical strategy, based on preoperative localization by MRI, has been developed for the treatment of retrorectal tumours.
Long-term follow-up of a randomized clinical trial comparing Beger with pylorus-preserving Whipple procedure for chronic pancreatitis
Authors: Müller M W , Friess H , Martin D J , Hinz U , Dahmen R , Büchler M W
Published: October 2007

Background

Duodenum-preserving pancreatic head resection according to Beger and the pylorus-preserving Whipple (ppWhipple) procedure were compared in patients with chronic pancreatitis (CP) in a randomized clinical trial. Perioperative data and short-term outcome have been reported previously. The present study evaluated long-term follow-up.

Methods

Forty patients were enrolled originally, 20 in each group. Long-term follow-up included mortality, morbidity, pain status, occupational rehabilitation, quality of life (QoL), and endocrine and exocrine function at median follow-up of 7 and 14 years.

Results

One patient who had a ppWhipple procedure was lost to follow-up. There were five late deaths in each group. No differences were noted in pain status and exocrine pancreatic function. Loss of appetite was significantly worse in the ppWhipple group at 14 years' follow-up, but there were no other differences in QoL parameters examined. After 14 years, diabetes mellitus was present in seven of 15 patients who had the Beger procedure and 11 of 14 patients after ppWhipple resection (P = 0·128).

Conclusion

After long-term follow-up of up to 14 years early advantages of the Beger procedure were no longer present.
Effect of hospital volume on outcome of pancreaticoduodenectomy in Italy
Authors: Balzano G , Zerbi A , Capretti G , Rocchetti S , Capitanio V , Di Carlo V
Published: October 2007

Background

An inverse relationship between hospital volume and death following pancreatico duodenectomy (PD) has been reported from several countries. The aim of this study was to assess the volume–outcome effect of PD in Italy.

Methods

The study group comprised 1576 patients who underwent PD in 2003. Hospitals were allocated to four volume groups: low volume, five PDs or fewer; medium volume, six to 13 PDs; high volume, 14 to 51 PDs; and very high volume, two hospitals that performed 89 and 104 PDs.

Results

Some 221 hospitals performed at least one PD in 2003; hospital volume was low in 74·7 per cent, medium in 17·6 per cent, high in 6·8 per cent and very high in 0·9 per cent. The overall mortality rate was 8·1 per cent. Increasing hospital volume was associated with a significantly reduced mortality rate: 12·4 per cent (adjusted odds ratio (OR) 1·000) for low-volume, 7·8 per cent (OR 0·611) for medium-volume, 5·9 per cent (OR 0·466) for high-volume and 2·6 per cent (OR 0·208) for very high-volume hospitals. Length of postoperative stay was reduced in very high-volume hospitals (P < 0·001).

Conclusion

The outcome of PD in Italy is dependent on hospital volume and a policy of centralization may therefore be appropriate.
Identification of a Potent Inhibitor of Human Dual‐Specific Phosphatase, VHR, from Computer‐Aided and NMR‐Based Screening to Cellular Effects
Authors: Shi Zhe , Tabassum Sartaj , Jiang Wei , Zhang Jiahai , Mathur Suvigya , Wu Jihui , Shi Yunyu
Published: October 2007

Human vaccinia H1‐related phosphatase (VHR) is a dual‐specific phosphatase (DSPs) that plays an important role in the mitogen‐activated protein (MAP) kinase cascade regulation. It is also a potential drug target for diseases that are related to immune response. By combining a virtual and NMR‐based ligand‐screening strategy, we successfully identified four VHR inhibitors, of which GATPT ((glucosamine‐aminoethoxy)triphenyltin) can bind to VHR with a Ki value of 2.54 μM. The putative binding mode of GATPT was constructed by a molecular docking simulation to provide structural insights into the ligand‐binding mechanism. Furthermore, we found that this compound can significantly inhibit the dephosphorylation of the extracellular regulated kinases (ERKs), and c‐Jun N‐terminal kinases (JNKs) and block the G1–S phase transition in the cell cycle. Therefore, GATPT is a promising lead structure for designing more effective inhibitors of VHR.
Synthesis, Structure and Emission Properties of Spirocyclic Benzofuranones and Dihydroindolones: A Domino Insertion–Coupling–Isomerization– Diels–Alder Approach to Rigid Fluorophores
Authors: D'Souza Daniel M. , Kiel Alexander , Herten Dirk‐Peter , Rominger Frank , Müller Thomas J. J.
Published: October 2007

An alkynoyl ortho‐iodo phenolester or alkynoyl ortho‐iodo anilides and propargyl allyl ethers react under Sonogashira coupling conditions in the sense of an insertion–coupling–isomerization–Diels–Alder hetero domino reaction to furnish (tetrahydroisobenzofuran)‐spirobenzofuranones and ‐spirodihydroindolones in good yields. Many representatives can be crystallized and single crystal structure analyses display steric and electronic substituent effects on the torsional angles of the terminal (hetero)aryl groups and the central cis,trans‐butadiene fragment. DFT computations reveal that in the final pericyclic step the Diels–Alder termination is by far thermodynamically and kinetically favored over a possible Claisen rearrangement. Compounds of this new class of spirocyclic compounds possess large Stokes shifts and fluoresce intensively with blue over green to orange colors. As a consequence of the spirocyclic rigidity fluorescence lifetimes and quantum yields are rather high in some cases.
Determination of absolute configurations by X‐ray crystallography and 1H NMR anisotropy
Authors: Harada Nobuyuki
Published: October 2007

To determine the absolute configurations of chiral compounds, many spectroscopic and diffraction methods have been developed. Among them, X‐ray crystallographic Bijvoet method, CD exciton chirality method, and the combination of vibrational circular dichroism and quantum mechanical calculations are of nonempirical nature. On the other hand, X‐ray crystallography using a chiral internal reference, and 1H NMR spectroscopy using chiral anisotropy reagents are relative and/or empirical methods. In addition to absolute configurational determinations, preparations of enantiopure compounds are strongly desired. As chiral reagents useful for both the preparation of enantiopure compounds by HPLC separation and the simultaneous determination of their absolute configurations, we have developed camphorsultam dichlorophthalic acid (CSDP acid) for X‐ray crystallography and 2‐methoxy‐2‐(1‐naphthyl)propionic acid (MαNP acid) for 1H NMR spectroscopy. In this review, the principles and applications of these X‐ray and NMR methods are explained using mostly our own data. Chirality, 2008. © 2007 Wiley‐Liss, Inc.
Conformation and Interaction of a d,l‐Alternating Peptide with a Bilayer Membrane: X‐ray Reflectivity, CD, and FTIR Spectroscopy
Authors: Küsel Andrea , Khattari Ziad , Schneggenburger Philipp E. , Banerjee Arnab , Salditt Tim , Diederichsen Ulf
Published: October 2007

Peptides with alternating amino acid configuration provide helical secondary structures that are especially known from the membrane channel and pore‐forming gramicidin A. In analogy to this natural d,l‐alternating pentadecapeptide, the potential of d,l‐alternating peptides for membrane insertion is investigated using the model dodecamer peptide H‐(Phe‐Tyr)5‐Trp‐Trp‐OH. This aromatic peptide is introduced as a novel pore‐forming synthetic analogue of gramicidin A. It forms a well‐organized homodimer similar to one of the gramicidin A transmembrane motifs. X‐ray reflectivity measurements are performed on solid‐supported peptide–lipid complexes to obtain information about the influence of the artificial dodecamer peptide on the bilayer parameters. In addition, Fourier‐transform infrared (FTIR) and circular dichroism (CD) spectroscopic studies determine the conformational state of H‐(Phe‐Tyr)5‐Trp‐Trp‐OH within the model membrane. Site‐specific iodine labeling assists in determining the topology of the membrane‐embedded peptide by pinpointing the position of the iodine label within the bilayers.
Essential role of antigen‐presenting cell‐derived BAFF for antibody responses
Authors: Bergamin Fabio , Vincent Isabelle E. , Summerfield Artur , McCullough Kenneth C.
Published: October 2007

Antigen‐presenting cells (APC) are directly involved in survival, growth and differentiation of naive B cells and in immunoglobulin class switch recombination. Less is known about the contribution of APC to memory B cell responses. We employed an in vitro model to investigate the secondary humoral response against foot‐and‐mouth disease virus, with cells from a natural host of the virus – the pig. This response is T cell‐dependent. Under conditions of limited T cell help, defined as a low T‐to‐B cell ratio or by the replacement of T cells with interleukin‐2 only, the antibody response was dependent on APC. These included monocytes and monocyte‐derived DC, but not plasmacytoid DC. APC mediated their help through soluble factors, particularly soluble B cell‐activating factor belonging to the TNF family (BAFF). Our results suggest that the ‘ménage à trois‘ concept, saying that both APC and T cells have a direct effect in B cell activation, is also valid for secondary B cell responses, and imply an important role for BAFF under conditions that might be physiologically relevant in secondary lymphoid organs.
Pathogenic T cells in MOBP‐induced murine EAE are predominantly focused to recognition of MOBP21F and MOBP27P epitopic residues
Authors: Kaushansky Nathali , Zilkha‐Falb Rina , Hemo Reut , Lassman Hans , Eisenstein Miriam , Sas Aldema , Ben‐Nun Avraham
Published: October 2007

Myelin‐associated oligodendrocytic basic protein (MOBP) is a central nervous system (CNS)‐specific myelin constituent important in stabilizing the unique multi‐layered structure of the CNS‐myelin sheath. Although autoimmunity against MOBP has been associated with multiple sclerosis pathogenesis, anti‐MOBP pathogenic T cells have been poorly investigated as compared to T cells against other encephalitogenic myelin proteins. We have recently determined MOBP15–36 as the major encephalitogenic epitope of MOBP for SJL/J mice. In this study, epitope‐specificity was dissected to the level of residues crucial for activation/control of MOBP‐specific encephalitogenic T cells. Structural bioinformatic analysis of MOBP15–36/I‐As interaction and experimental data have determined MOBP21F and MOBP27P of I‐As‐binding nonameric core epitope (MOBP20–28) as TCR‐contact residues critical for functional activation of encephalitogenic MOBP‐specific T cells. Accordingly, the non‐encephalitogenic/nonstimulatory pMOBP16–21A27A‐33 inhibited encephalitogenic MOBP‐reactive T cells, shifted their cytokine secretion profile, and effectively suppressed pMOBP15–36‐induced EAE. Moreover, pMOBP16–21A27A‐33 fully reversed ongoing clinical EAE induced by whole MOBP as well as by pMOBP15–36. Data show that encephalitogenic MOBP‐reactive T cells are predominantly focused to recognition of MOBP21F and MOBP27P, and suggest that both their selection and control are governed by MOBP21F and MOBP27P epitopic residues. Such focused epitopic recognition may affect profoundly on peripheral self‐tolerance to MOBP and on potential altered peptide ligand‐mediated therapy of MOBP‐related autoimmune pathogenesis.
Critical role for Ipaf in Pseudomonas aeruginosa‐induced caspase‐1 activation
Authors: Franchi Luigi , Stoolman Joshua , Kanneganti Thirumala‐Devi , Verma Amrisha , Ramphal Reuben , Núñez Gabriel
Published: October 2007

Pseudomonas aeruginosa is an opportunistic Gram‐negative human pathogen that is responsible for a broad range of infections in individuals with a variety of predisposing conditions. After infection, P. aeruginosa induces a marked inflammatory response in the host. However the mechanisms involved in bacterium recognition and induction of immune responses are poorly understood. Here we report that the Nod‐like receptor family member Ipaf is required for optimal bacterial clearance in an in vivo model of P. aeruginosa lung infection. Further analysis showed that bacterial flagellin was essential for caspase‐1 and IL‐1β and this activity depended on Ipaf and the adaptor ASC but not TLR5. Notably, P. aeruginosa induced macrophage cell death and this event relied on flagellin and Ipaf but not on ASC. Analysis of Pseudomonas mutants revealed that different amino acid residues of flagellin were critical for sensing by Ipaf and TLR5. Finally, activation of caspase‐1 and IL‐1β secretion by P. aeruginosa required a functional type III secretion system, but not the effector molecules ExoS, ExoT and ExoY. These results provide new insight into the interaction of P. aeruginosa with host macrophages and suggest that distinct regions of flagellin are sensed by Ipaf and TLR5.
Non‐redundant role for IL‐7R signaling for the survival of CD8+ memory T cells
Authors: Carrio Roberto , Rolle Cleo E. , Malek Thomas R.
Published: October 2007

IL‐7 and IL‐15 are important cytokines for CD8 memory T cells. However, the extent that IL‐7 is essential for CD8 T cell memory remains unclear because blocking IL‐7 in vivo results in near complete inhibition of T cell development with the few mature T cells exhibiting functional abnormalities. To bypass this complication, CD8 memory development was examined utilizing a mouse model where transgenic IL‐7Rα was selectively expressed in the thymus of IL‐7Rα–/– mice. T cell development was corrected but the resulting peripheral T cells were essentially IL‐7 non‐responsive. Activation of IL‐7R‐defective OT‐I CD8+ T cells with OVA257–264 and IL‐2 readily yielded CTL. Upon further culture with IL‐15, these CTL expressed phenotypic and functional properties of central memory‐like cells. Thus, IL‐7R‐defective CD8+ T cells do not exhibit intrinsic defects in effector or memory development. When IL‐7R‐defective OT‐I CTL were adoptively transferred into normal or IL‐15–/– recipient mice in a non‐inflammatory setting, they converted into memory‐like cells, but did not persist, which was even more striking in IL‐15–/– recipients. This poor persistence was rescued after expression of transgenic Bcl‐2 in IL‐7R‐defective OT‐I T cells. Collectively, these data indicate that IL‐7 is non‐redundantly required for the survival of CD8 memory T cells.
Luminescent Organically Templated Lanthanide Oxalate–Selenate Hybrids
Authors: Feng Mei‐Ling , Mao Jiang‐Gao
Published: October 2007

Hydrothermal reactions of lanthanide nitrates with selenic acid, sodium oxalate, and organic amines led to two series of new organically templated lanthanide oxalate–selenate hybrids with 2D‐layer or 3D‐network structures, namely, Ln2(SeO4)2(C2O4)(H2O)4·pip (Ln = Eu 1; Tb 2; Dy 3; Er 4; Yb 5) (pip = piperazine) and [H2pip]2[Ln2(SeO4)2(C2O4)3]·H2O (Ln = Er 6; Yb 7; Lu 8; Y 9). Their structures were established by X‐ray single‐crystal diffraction. Isostructural compounds 1–5 feature a 2D inorganic–organic hybrid neutral layer of Ln2(SeO4)2(C2O4)(H2O)4. The neutral piperazine molecules are located at the interlayer spaces and interconnect with the inorganic skeleton through hydrogen bonds. Compounds 6–9 are isostructural and possess 3D pillared layered architectures composed of lanthanide oxalate layers bridged by selenate anions (the pillar). The template cations are located at the tunnels of the structure. Compounds 1, 2, and 3 display emission bands in the red‐, green‐, and pink‐light regions, respectively, and these compounds have lifetimes of 0.178, 0.962, and 0.276 ms, respectively. Compounds 6 and 7 both exhibit emission bands in the near‐IR region. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)