bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mathematical Modelling and Computer Simulation of Linear Polymer Degradation: Simple Scissions
Authors: Bose Sonia M. , Git Yoav 
Published: May 2004

AbstractSummary: Degradation of a polymer in a reactor by the degrading agent(s) follows a distinct pattern, primarily influenced by structural integrity and reactor environment. This distinct pattern is recorded in the changes in the evolved molecular weight distribution (MWD) or polymer chain length distribution (PCLD) curve characteristics from the initial intact state. Modern size exclusion chromatography (SEC) is the best laboratory‐based method that can clearly provide these plots in the form of chromatogram; however, detailed molecular information is not available. The nature of molecular destruction can be well‐characterised if the distinct MWD shift patterns can be simulated to fingerprint the different chain scission dynamics. This is investigated by our current research using the power of computer simulation techniques to gain insight into the polymer ageing processes. One such technique for studying simple decay processes is presented here, and the results are compared with experimental findings. The concept of a binary tree scission model is introduced to show chain rupture as a sequence of probabilistic events and as a non‐linear function of time. Two new mathematical algorithms, an iterative Monte Carlo structured probability scheme and a semi‐iterative algebraic exact statistical formulation method, are investigated to implement this model and simulate the evolution of resultant temporal MW distribution. The latter, an innovative approach to mathematical modelling, has the potential to generate a statistically perfect instant MWD decay curve. A statistical comparison of the product yield is presented from the data obtained using a wide variety of simulated scission regimes to determine the sources of variability.Simulated MWD lateral shift for percent cut scission model showing deviation from the initial MWD (red) over degradation time zones Tj(0 ≥ j ≤ 9) with bimodal and curve broadening effect due to accumulation of varied percent cut range 5–30%.imageSimulated MWD lateral shift for percent cut scission model showing deviation from the initial MWD (red) over degradation time zones Tj(0 ≥ j ≤ 9) with bimodal and curve broadening effect due to accumulation of varied percent cut range 5–30%.
Urotensin‐II receptor peptide agonists
Authors: Carotenuto Alfonso , Grieco Paolo , Novellino Ettore , Rovero Paolo 
Published: May 2004

AbstractUrotensin II (U‐II) has been known for over 30 years as an important teleost fish hormone, but only recently has it been recognized as the endogenous ligand of a new human G‐protein‐coupled receptor (GPCR) homologous to the GPR14 orphan receptor from rat. Human U‐II was found to be a potent vasoconstrictor, widely distributed in human tissues, possibly contributing to several human cardiovascular diseases. It thus has become a major target of medicinal chemistry research. The common structural feature of U‐II peptides from different species is the C‐terminal portion, characterized by the disulfide bridged cyclic hexapeptide Cys‐Phe‐Trp‐Lys‐Tyr‐Cys. The few structure–activity relationship studies reported to date attributed a critical role to this portion, with the Trp‐Lys‐Tyr motif appearing as the key determinant of U‐II bioactivity. Consequently, this shorter cyclic peptide was used as a template for the development of several synthetic analogues, among which a superagonist, termed P5U: H‐Asp‐cyclo(Pen‐Phe‐Trp‐Lys‐Tyr‐Cys)‐Val‐OH. Conformational studies confirmed the important role of hU‐II C‐terminal cyclic portion, enabling the development of 3D pharmacophore models. These findings should lead to the design of new, potent and selective analogues, acting as agonist or antagonist at the human U‐II receptor, finally contributing to a deeper comprehension of the (patho)physiological significance of this peptide. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 5, 577–588, 2004
A conservative integral for bimaterial notches subjected to thermal stresses
Authors: Banks‐Sills Leslie , Ishbir Chaim 
Published: May 2004

AbstractIn this investigation, a conservative integral based on the Betti reciprocal principle is developed to obtain stress intensity factors for a bimaterial notch in which the body is subjected to a thermal load. The bonded materials are linear elastic, isotropic and homogeneous. According to the linear theory of elasticity, stresses in the neighbourhood of the notch tip are generally singular as a result of the mismatch of the elastic constants. Eigenvalues and eigenfunctions depend upon the mechanical properties and wedge angles. They may be real, complex or power‐logarithmic. Real and complex eigenvalues are considered in this study. The stress intensity factor represents the amplitude of the stress singularity and depends upon material properties, geometry and load or temperature. Because of the highly singular behaviour of one of the integrals that is part of the conservative integral, the former is carried out by a hybrid analytical/numerical scheme.The finite element method is employed to obtain displacements caused by the temperature distribution in the body. The conservative integral is applied to several problems appearing in the literature. Both good agreement between those results and the ones obtained here, as well as path stability for all problems is attained. A wide range of material parameters is also studied. Copyright © 2004 John Wiley & Sons, Ltd.
A stabilized volume‐averaging finite element method for flow in porous media and binary alloy solidification processes
Authors: Zabaras Nicholas , Samanta Deep 
Published: May 2004

AbstractA stabilized equal‐order velocity–pressure finite element algorithm is presented for the analysis of flow in porous media and in the solidification of binary alloys. The adopted governing macroscopic conservation equations of momentum, energy and species transport are derived from their microscopic counterparts using the volume‐averaging method. The analysis is performed in a single domain with a fixed numerical grid. The fluid flow scheme developed includes SUPG (streamline‐upwind/Petrov–Galerkin), PSPG (pressure stabilizing/Petrov–Galerkin) and DSPG (Darcy stabilizing/Petrov–Galerkin) stabilization terms in a variable porosity medium. For the energy and species equations a classical SUPG‐based finite element method is employed. The developed algorithms were tested extensively with bilinear elements and were shown to perform stably and with nearly quadratic convergence in high Rayleigh number flows in varying porosity media. Examples are shown in natural and double diffusive convection in porous media and in the directional solidification of a binary‐alloy. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of the polymer of a dipyrrolyl monomer by pyrolysis mass spectrometry
Authors: Ertas Merve , Hacaloglu Jale , Toppare Levent 
Published: May 2004

AbstractIn this work, characterization of a homopolymer of succinic acid bis(4‐pyrrol‐1‐ylphenyl) ester prepared by galvonastatic polymerization was carried out by direct pyrolysis mass spectrometry. Although decomposition of the monomer yielding mainly butadionic acid and pyrrole occurred under the galvonastatic polymerization conditions, growth of the polymer through the pyrrole moieties was also achieved, yielding a ladder‐type polymer film. The polypyrrole chains contained both quinoid and aromatic units as in the case of polypyrrole, yet the extent of network structure was significantly diminished. A three‐step mechanism is proposed for the thermal decomposition process. The first step involves the cleavage of C4H4NC6H4O end groups. In the second step, decomposition of phenyl ester units and polypyrrole chains having quinoid structure takes place. The final stage of thermal degradation was attributed to decomposition of polypyrrole chains having aromatic structure. Copyright © 2004 Society of Chemical Industry
Robust linear anti‐windup synthesis for recovery of unconstrained performance
Authors: Grimm Gene , Teel Andrew R. , Zaccarian Luca 
Published: May 2004

AbstractFixed order anti‐windup augmentation is addressed by considering the dynamics of the mismatch between the constrained and unconstrained responses. The method utilizes LMIs, and the result parallels other recent LMI‐based anti‐windup synthesis methods. Robustness is directly addressed—which is not done in previous LMI work on anti‐windup. An optimal LMI‐based synthesis procedure is provided for static and plant‐order linear anti‐windup augmentation and the performance of the resulting design strategy is shown via a simulation example. Copyright © 2004 John Wiley & Sons, Ltd.
Control of manipulators in a constrained workspace by means of linked invariant sets
Authors: Blanchini Franco , Pellegrino Felice Andrea , Visentini Luca 
Published: May 2004

AbstractWe propose a new technique for controlling manipulators in constrained environments. Based on recent developments on constrained control theory, our approach basically consists in covering the admissible region of the configuration space by partially overlapping convex polyhedra arbitrarily fixed and forming a connected family. Each of these polyhedra, defined in the configuration space, is suitably extended in the state‐space (i.e. configuration‐plus‐velocity space) in order to maintain all the original connections among regions and to be a tracking domain of attraction for the system, i.e. a set of initial states from which a reference signal can be asymptotically approached without constraints violation during the transient. The connection path is not generated a priori, but it is automatically produced on‐line by a hierarchical feedback controller. A high‐level controller selects the confining polyhedron, to which the current state has to be transferred, which is the closest to the one containing the target reference. A low‐level controller solves the problem of locally tracking a suitable crossing point to the desired new region under constraints. The robustness of the scheme as well as the control effort constraints are also taken into account. Copyright © 2004 John Wiley & Sons, Ltd.
An SVD based strategy for receding horizon control of input constrained linear systems
Authors: Rojas Osvaldo J. , Goodwin Graham C. , Serón María M. , Feuer Arie 
Published: May 2004

AbstractA sub‐optimal receding horizon control strategy for input constrained linear systems is presented. The strategy is based on a singular value decomposition (SVD) of the Hessian of the quadratic performance index generally considered in model predictive control (MPC). The singular vectors are employed to generate a basis function expansion of the unconstrained solution to the finite horizon optimal control problem. At each sampling time, a feasible control sequence is determined by selecting a variable subset of the basis representation. No solution to the associated quadratic program is needed. For cases in which the Hessian is poorly conditioned, the proposed strategy can provide a sub‐optimal solution with minimal performance degradation. Properties of the singular values of the Hessian are also studied: it is shown that, for sufficiently long prediction horizons, the singular values are arbitrarily close to the magnitude of the energy density spectrum of the system seen by the performance index. Copyright © 2004 John Wiley & Sons, Ltd.
Extended anti‐windup control schemes for LTI and LFT systems with actuator saturations
Authors: Wu Fen , Soto Marco 
Published: May 2004

AbstractIn this paper, the popular anti‐windup control scheme will be extended in two important directions. The first scenario is the control of LTI systems subject to actuators with both magnitude and rate constraints. The second case of extension is LFT systems with input saturations. Based on the extended Circle criterion, we will develop convex anti‐windup control synthesis conditions in the form of LMIs for each class of systems. The explicit anti‐windup controller formula are also provided to facilitate compensator construction. The effectiveness of proposed anti‐windup control schemes will be demonstrated using a flight control example. Copyright © 2004 John Wiley & Sons, Ltd.
Rheological Properties of Pastes Obtained from Starches Derived from Immature Cereal Kernels
Authors: Gambuś Halina , Gumul Dorota , Juszczak Lesław 
Published: May 2004

AbstractThe results presented in this work concern the starches of three basic varieties of cereal cultivated in Poland – wheat, rye and barley – harvested at different stages of maturity in 1997 and 1998. Starches from these kernels were isolated by a laboratory method. The flow curves and thixotropic properties of 5% starch pastes at 50°C and controlled shear rates between 0 and 600 s−1 were obtained. All the investigated starch pastes were non‐Newtonian, plastic and thixotropic fluids, that differed in their values of yield stress. The pastes from immature cereal starches were characterised by a higher plasticity because they needed a higher shear stress (τ) to achieve the yield stress (τ01) in comparison with the pastes from the mature cereal starches. At applied shear stress the pastes from the “immature” starches had a higher thixotropy in comparison with the “mature” ones. Pastes from immature starch were more susceptible towards shearing forces but at the same time they exhibited a better ability to rebuild their structure. The description of the flow curves by the Ostwald‐de Waele equation allows the conclusion that pastes from the immature starches have a higher structural viscosity. In addition, the application of the Casson model allows to describe the flow curves and determine the yield stress and the plasticity properties of the investigated pastes. However, the viscosity values calculated from the Casson model do not reflect differences in viscosity among the samples.
Chlamydia pneumoniae and newly diagnosed asthma: a case‐control study in 1 to 6‐year‐old children
Authors: KORPPI Matti , PALDANIUS Mika , HYVÄRINEN Anne , NEVALAINEN Aino , HUSMAN Tuula 
Published: May 2004

Objective:  The aim of the study was to evaluate the association between antibodies to Chlamydia pneumoniae and the onset of asthma in children.Methodology:  In 1996–2000, 122 children aged 1–6 years, who were treated for new asthma as inpatients or outpatients in our hospital, were recruited. For each patient, two controls, matched by age, sex and municipality, were randomly selected from the same population. In 2000, 104 serum samples were available from patients (85%) and 120 from controls (49%) for microimmunofluorescence (MIF) assay for C. pneumoniae and C. trachomatis antibodies, and for enzyme immunoassay (EIA) for C. pneumoniae antibodies.Results:  In EIA, the median IgG concentrations were 20 EIU (EIA units) in the patients, and 16 EIU in the controls. IgG was positive (> 30 EIU) in 37 (36%) patients and in 36 (31%) controls. IgA was positive (> 12 EIU) in four (4%) patients and in eight (7%) controls. In MIF, four (4%) patients and seven (6%) controls were IgG positive, and seven were also IgA positive. IgM antibodies were detected in four children by EIA, and in none by MIF.Conclusion:  IgG antibodies to C. pneumoniae, though common in 1 to 6‐year‐old children as detected by EIA, did not differ between newly diagnosed asthma patients and controls in this case‐control study.
Polymorphism of the promoter region of prostacyclin synthase gene in chronic thromboembolic pulmonary hypertension
Authors: AMANO Shinya , TATSUMI Koichiro , TANABE Nobuhiro , KASAHARA Yasunori , KUROSU Katsushi , TAKIGUCHI Yuichi , KASUYA Yoshitoshi , KIMURA Sadao , KURIYAMA Takayuki 
Published: May 2004

Objective:  Decreased expression of prostacyclin synthase (PGIS) is observed in the lung vasculature of patients with pulmonary arterial hypertension and the biosynthesis of prostacyclin (PGI2) may be impaired in chronic thromboembolic pulmonary hypertension (CTEPH). Whether it is genetically determined or develops as the disease progresses is unclear. A variable‐number tandem repeat (VNTR) polymorphism has been detected in the 5′‐upstream promoter region of the PGIS gene. It has been demonstrated that the alleles vary in size from three to seven repeats of nine base pairs, and transcriptional activity increased with the number of repeats. The purpose of the present study was to elucidate the association between the VNTR polymorphisms of the PGIS gene and CTEPH in Japanese subjects.Methodology:  Ninety patients with CTEPH and 144 control subjects were investigated for the presence of VNTR polymorphisms. Sixty‐two blood samples were obtained from CTEPH patients and the plasma concentrations of prostacyclin and thromboxane A2 metabolites were measured.Results:  VNTR polymorphisms in the prostacyclin synthase gene were grouped into L alleles (five, six and seven repeats) and S alleles (three and four repeats). The overall distribution of the alleles and genotypes were not significantly different between CTEPH patients and the control subjects. The patients with the LL genotype had higher plasma concentrations of 6‐keto‐prostaglandin F1α than patients with the LS and SS genotypes.Conclusions:  Our results suggested that the specific VNTR polymorphism in the 5′‐upstream promoter region of the PGIS gene regulated prostacyclin production, but did not seem to be associated with the development of CTEPH in this patient population.
Dorsal buccal mucosal graft urethroplasty by a ventral sagittal urethrotomy and minimal‐access perineal approach for anterior urethral stricture
Authors: Gupta N.P. , Ansari M.S. , Dogra P.N. , Tandon S. 
Published: May 2004

In the mini‐review section of this issue, the use of buccal mucosal grafts in urethroplasty is described and the authors raise the point that it may now be the ‘reference’ standard. In this section, authors from New Dehli describe these technique of anterior urethral reconstruction for long strictures using buccal mucosal grafts. Their rather novel approach is of interest, and they report good results with up to 16 months of follow‐up.OBJECTIVETo present the technique of dorsal buccal mucosal graft urethroplasty through a ventral sagittal urethrotomy and minimal access perineal approach for anterior urethral stricture.PATIENTS AND METHODSFrom July 2001 to December 2002, 12 patients with a long anterior urethral stricture had the anterior urethra reconstructed, using a one‐stage urethroplasty with a dorsal onlay buccal mucosal graft through a ventral sagittal urethrotomy. The urethra was approached via a small perineal incision irrespective of the site and length of the stricture. The penis was everted through the perineal wound. No urethral dissection was used on laterally or dorsally, so as not to jeopardize the blood supply.RESULTSThe mean (range) length of the stricture was 5 (3–16) cm and the follow‐up 12 (10–16) months. The results were good in 11 of the 12 patients. One patient developed a stricture at the proximal anastomotic site and required optical internal urethrotomy.CONCLUSIONDorsal buccal mucosal graft urethroplasty via a minimal access perineal approach is a simple technique with a good surgical outcome; it does not require urethral dissection and mobilization and hence preserves the blood supply.
Nocturia and depression
Authors: Asplund R. , Henriksson S. , Johansson S. , Isacsson G. 
Published: May 2004

OBJECTIVETo assess the possible relationship between major depression (MD) and nocturia.SUBJECTS AND METHODSAn unselected group of adult men and women, living in the city of Östersund, Sweden, were sent a postal questionnaire containing questions on somatic and mental health, sleep, sleepiness and nocturia. For depression diagnostics the Major Depression Inventory (MDI) was used.RESULTSThe mean (sd) ages of the men and women were 48.0 (18.2) and 50.1 (19.1) years, respectively. Two or more nocturnal micturition episodes occurred in 15.6% of the men and 16.5% of the women. In a multiple logistic regression analysis independent correlates (with 95% confidence intervals) for ≥ 2 nocturnal voids in men were: MD 6.5 (2.6–15.6); health, fair vs good, 1.8 (1.0–3.9); health, poor vs good, 2.7 (1.1–4.8); age, 60–74 vs 18–29, 3.6 (1.5–8.4) and age ≥ 75 vs 18–29 6.7 (2.6–17.4); and in women: MD 2.8 (1.3–6.3); health, fair vs good, 1.9 (1.1–3.2); health, poor vs good, 4.3 (2.6–8.2); age, 60–74 vs 18–29, 3.8 (1.8–7.8), and age ≥ 75 vs 18–29, 8.6 (4.0–18.6). Age < 60 years was deleted by the logistic model in both sexes.CONCLUSIONMD is associated with a six‐fold increase in nocturia in men and a three‐fold increase in women, after accounting for age and health. Possible pathogenetic mechanisms of this relationship may involve both increased nocturnal diuresis via a disturbed 24‐h rhythm of antidiuretic hormone secretion, and a decrease in nocturnal bladder capacity through a central and/or peripheral serotonergic effect.
Concurrent radical retropubic prostatectomy and inguinal hernia repair through a modified Pfannenstiel incision
Authors: Manoharan M. , Gomez P. , Soloway M.S. 
Published: May 2004

Authors from Miami describe their technique of concurrent radical retropubic prostatectomy and inguinal hernia repair through a modified Pfannenstiel incision. They found this approach to be ideal for performing both operations at the same time, allowing a tension‐free mesh hernia repair with excellent exposure of the pelvic structures.An interesting paper from authors in New York reviews patients who had both bladder and lung cancer. Their findings are important in terms of a potential guideline to urologists who have patients with these conditions, and are, for example, faced with the decision as to whether they should operate on someone who has a history of lung cancer but now has bladder cancer.In another paper from the New York area, authors describe the effect on morbidity and mortality of bone metastasis in patients with RCC. They found the effect to be considerable, and suggest a possible role for bisphosphonates.OBJECTIVETo describe a technique for concurrent radical retropubic prostatectomy (RRP) and inguinal hernioplasty, using a modified Pfannenstiel incision.PATIENTS AND METHODSRRP is usually done through a midline lower abdominal incision but some patients with localized prostate cancer have an inguinal hernia. Concurrent inguinal hernia repair at the time of RRP with the usual method is only possible by either a preperitoneal mesh repair or formal hernioplasty, requiring an additional incision(s). A 10–12 cm Pfannenstiel incision is made along the pubic hairline centred over the pubic symphysis, and a ‘Y’‐shaped incision in the rectus sheath. The rectus muscle is split vertically along the midline, followed by RRP. After removing the prostate and completing the anastomosis, the surgeon identifies the inguinal canal along the inferior and lateral aspect of the transverse incision and uses a formal tension‐free hernioplasty with a 3 × 5 cm polypropylene mesh. We used this technique in fifteen concurrent inguinal hernioplasties (two bilateral hernias and thirteen unilateral) at the time of RRP, with no additional incisions, using the formal tension‐free Lichtenstein technique. One patient with bilateral hernias had a right indirect inguinal hernia, and all the remaining men had a direct inguinal hernia.RESULTSAll patients were discharged 2 days after surgery, with no complications associated with the procedure and no recurrences; however, the follow‐up was short (mean 5.5 months).CONCLUSIONA modified Pfannenstiel incision is ideal for concurrent RRP and inguinal hernioplasty, providing excellent exposure of the pelvic structures and allowing the surgeon to use a formal tension‐free mesh hernioplasty through the same incision. Wound healing and cosmetic results are excellent.