bluuebunny/crossref_metadata_2025 huggingface dataset:
Laplacian and vibrational spectra for homogeneous graphs
Authors: Chung Fan R. K. , Sternberg Shlomo
Published: June 2007

A homogeneous graph is a graph togerther with a group that acts transitively on vertices as symmertries of the graph. We consider Laplacians of homogeneous graphs and generalizations of Laplacians whose eigenvalues can be associated with various equilibria of forces in molecules (such as vibrational modes of buckyballs). Methods are given for calculating such eigenvalues by combining concepts and techniques in group representation theory, gauge theory and graph theory.
Total chromatic number of complete r‐partite graphs
Authors: Chew K. H. , Yap H. P.
Published: June 2007

Rosenfeld (1971) proved that the Total Colouring Conjecture holds for balanced complete r‐partite graphs. Bermond (1974) determined the exact total chromatic number of every balanced complete r‐partite graph. Rosenfeld's result had been generalized recently to complete r‐partite graphs by Yap (1989). The main result of this paper is to prove that the total chromatic number of every complete r‐partite graph G of odd order is Δ (G) + 1. This result gives a partial generalization of Bermond's theorem.
On the stability number of AH‐free graphs
Authors: Hertz A. , de Werra D.
Published: June 2007

We describe a new class of graphs for which the stability number can be obtained in polynomial time. The algorithm is based on an iterative procedure that, at each step, builds from a graph G a new graph Gl that has fewer nodes and has the property that α(Gl) = α(G) − 1.

This new class of graphs is different from the known classes for which the stability number can be computed in polynomial time. © 1993 John Wiley & Sons, Inc.
A note on graphs and sphere orders
Authors: Scheinerman Edward R.
Published: June 2007

A partially ordered set P is called a k‐sphere order if one can assign to each element a ∈ P a ball Ba in Rk so that a < b iff Ba ⊂ Bb. To a graph G = (V,E) associate a poset P(G) whose elements are the vertices and edges of G. We have v < e in P(G) exactly when v ∈ V, e ∈ E, and v is an end point of e. We show that P(G) is a 3‐sphere order for any graph G. It follows from E. R. Scheinerman [“A Note on Planar Graphs and Circle Orders,” SIAM Journal of Discrete Mathematics, Vol. 4 (1991), pp. 448–451] that the least k for which G embeds in Rk equals the least k for which P(G) is a k‐sphere order. For a simplicial complex K one can define P(K) by analogy to P(G) (namely, the face containment order). We prove that for each 2‐dimensional simplicial complex K, there exists a k so that P(K) is a k‐sphere order. © 1993 John Wiley & Sons, Inc.
A characterization of the smallest eigenvalue of a graph
Authors: Desai Madhav , Rao Vasant
Published: June 2007

It is well known that the smallest eigenvalue of the adjacency matrix of a connected d‐regular graph is at least − d and is strictly greater than − d if the graph is not bipartite. More generally, for any connected graph G = (V, E), consider the matrix Q = D + A where D is the diagonal matrix of degrees in the graph G and A is the adjacency matrix of G. Then Q is positive semidefinite, and the smallest eigenvalue of Q is 0 if and only if G is bipartite. We will study the separation of this eigenvalue from 0 in terms of the following measure of nonbipartiteness of G. For any S ⊆ V, we denote by emin(S) the minimum number of edges that need to be removed from the induced subgraph on S to make it bipartite. Also, we denote by cut(S) the set of edges with one end in S and the other in V − S. We define the parameter Ψ as.

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The parameter Ψ is a measure of the nonbipartiteness of the graph G. We will show that the smallest eigenvalue of Q is bounded above and below by functions of Ψ. For d‐regular graphs, this characterizes the separation of the smallest eigenvalue of the adjacency matrix from −d. These results can be easily extended to weighted graphs.
Bounds for the harmonious chromatic number of a graph
Authors: Krasikov I. , Roditty Y.
Published: June 2007

The upper bound for the harmonious chromatic number of a graph given by Zhikang Lu and by C. McDiarmid and Luo Xinhua, independently (Journal of Graph Theory, 1991, pp. 345–347 and 629–636) and the lower bound given by D. G. Beane, N. L. Biggs, and B. J. Wilson (Journal of Graph Theory, 1989, pp. 291–298) are improved.
Quasi‐median graphs and algebras
Authors: Bandelt Hans‐Jürgen , Mulder Henry Martyn , Wilkeit Elke
Published: June 2007

Scattered through the literature various structures occur that generalize median graphs and median algebras: quasi‐median graphs, retracts of Hamming graphs, graphs of finite windex, isotropic media, subdirect products of simplex algebras, certain ternary algebras, and so on. We connect them all up, provide some new generalizations of quasi‐median graphs, some new sets of axioms for quasi‐median algebras, and some shorter proofs as well.
The ramsey number r(k1 + c4, k5 − e)
Authors: Yuansheng Yang , Hendry G. R. T.
Published: June 2007

The graph K5 ‐ e is obtained from the complete graph K5 by deleting one edge, while K1 + C4 is obtained from K5 by deleting two independent edges. With the help of a computer it is shown that r(K1 + C4, K5 ‐ e) = 17. © 1995 John Wiley & Sons, Inc.
Squares, clique graphs, and chordality
Authors: Wallis W. D. , Wu Julin
Published: June 2007

We study the squares and the clique graphs of chordal graphs and various special classes of chordal graphs. Chordality conditions for squares and clique graphs are given. Several theorems concering chordal graphs are generalized. © 1996 John Wiley & Sons, Inc.
Insertible vertices, neighborhood intersections, and hamiltonicity
Authors: Ainouche A. , Schiermeyer I.
Published: June 2007

Let G be a simple undirected graph of order n. For an independent set S ⊂ V(G) of k vertices, we define the k neighborhood intersections Si = {v ϵ V(G)\S|N(v) ∩ S| = i}, 1 ≦ i ≦ k, with si = |Si|. Using the concept of insertible vertices and the concept of neighborhood intersections, we prove the following theorem.
Pseudo‐Interval Graphs
Authors: Brauner Erik O. , Brauldi Richard A. , Sneyd Elizabeth S. N.
Published: June 2007

We study a class of perfect graphs which, because they generalize interval graphs, we call pseudo‐interval graphs. Like interval graphs, their vertices correspond to intervals of a linearly ordered set, but a modified definition of intersection is used in order to determine edges. The complements of pseudo‐interval graphs are comparability graphs but unlike interval graphs, pseudo‐interval graphs are only weakly triangulated. We characterize trees and complements of trees which are pseudo‐interval graphs. Finally we determine all minimal non‐pseudointerval graphs on eight or fewer vertices whose complements are comparability graphs and which are weakly triangulated. © 1995 John Wiley & Sons; Inc.
Biclosure and bistability in a balanced bipartite graph
Authors: Amar Denise , Favaron Odile , Mago Pedro , Ordaz Oscar
Published: June 2007

The k‐biclosure of a balanced bipartite graph wiht color classes A and B is the graph obtained from G by recursively joining pairs of nonadjacent vertices respectively taken in A and B whose degree sum is at least k, until no such pair remains. A property P defined on all the balanced bipartite graphs of order 2n is k‐bistable if whenever G + ab has property P and dG(b) ≧ k then G itself has property P.

We present a synthesis of results involving, for some properties, P, the bistability of P, the k‐biclosure of G, the number of edges and the minimum degree. © 1995 John Wiley & Sons, Inc.
Measurement of brain microglial proliferation rates in vivo in response to neuroinflammatory stimuli: Application to drug discovery
Authors: Shankaran Mahalakshmi , Marino Michael E. , Busch Robert , Keim Carole , King Chelsea , Lee Jean , Killion Salena , Awada Mohamad , Hellerstein Marc K.
Published: June 2007

Microglial activation is emerging as an important etiologic factor and therapeutic target in neurodegenerative and neuroinflammatory diseases. Techniques have been lacking, however, for measuring the different components of microglial activation independently in vivo. We describe a method for measuring microglial proliferation rates in vivo using heavy water (2H2O) labeling, and its application in screening for drugs that suppress neuro‐inflammation. Brain microglia were isolated by flow cytometry as F4/80+, CD11b+, CD45low cells, and 2H enrichment in DNA was analyzed by gas chromatography/mass spectrometry. Basal proliferation rate was ∼1%/week and systemic administration of bacterial lipopolysaccharide (LPS) markedly increased this rate in a dose‐dependent manner. Induction of experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice by MOG35–55 peptide stimulated proliferation of CD45low microglia, which could be distinguished from the proliferation of CD45high infiltrating monocytes. Minocycline (45 mg/kg/day, i.p.) inhibited resident microglial proliferation in both the LPS and EAE models. Thirteen drugs were then screened for their ability to inhibit LPS‐stimulated microglia proliferation. Female C57BL/6 mice were given LPS (1 mg/kg), and concomitant drug treatment while receiving 2H2O label for 7 days. Among the drugs screened, treatment with isotretinoin dose‐dependently reduced LPS‐induced microglial proliferation, representing an action of retinoids unknown previously. Follow‐up studies in the EAE model confirmed that isotretinoin not only inhibited proliferation of microglia but also delayed the onset of clinical symptoms. In conclusion, 2H2O labeling represents a relatively high‐throughput, quantitative, and highly reproducible technique for measuring microglial proliferation, and is useful for screening and discovering novel anti‐neuroinflammatory drugs. © 2007 Wiley‐Liss, Inc.
Coherent anti‐stokes Raman scattering imaging of myelin degradation reveals a calcium‐dependent pathway in lyso‐PtdCho‐induced demyelination
Authors: Fu Yan , Wang Haifeng , Huff Terry B. , Shi Riyi , Cheng Ji‐Xin
Published: June 2007

Coherent anti‐Stokes Raman scattering (CARS) microscopy, which allows vibrational imaging of myelin sheath in its natural state, was applied to characterize lysophosphatidylcholine (lyso‐PtdCho)‐induced myelin degradation in tissues and in vivo. After the injection of lyso‐PtdCho into ex vivo spinal tissues or in vivo mouse sciatic nerves, myelin swelling characterized by the decrease of CARS intensity and loss of excitation polarization dependence was extensively observed. The swelling corresponds to myelin vesiculation and splitting observed by electron microscopy. The demyelination dynamics were quantified by the increase of g ratio measured from the CARS images. Treating spinal tissues with Ca2+ionophore A23187 resulted in the same kind of myelin degradation as lyso‐PtdCho. Moreover, the demyelination lesion size was significantly reduced upon preincubation of the spinal tissue with Ca2+free Krebs' solution or a cytosolic phospholipase A2(cPLA2) inhibitor or a calpain inhibitor. In accordance with the imaging results, removal of Ca2+or addition of cPLA2inhibitor or calpain inhibitor in the Krebs' solution remarkably increased the mean compound action potential amplitude in lyso‐PtdCho treated spinal tissues. Our results suggest that lyso‐PtdCho induces myelin degradation via Ca2+influx into myelin and subsequent activation of cPLA2and calpain, which break down the myelin lipids and proteins. The current work also shows that CARS microscopy is a potentially powerful tool for the study of demyelination. © 2007 Wiley‐Liss, Inc.
Thermoplastic Soy Protein Nanocomposites Reinforced by Carbon Nanotubes
Authors: Zheng Hua , Ai Fujin , Wei Ming , Huang Jin , Chang Peter R.
Published: June 2007

MWNTs of various sizes were compounded into SPI matrix by solution mixing and then compression‐molded into nanocomposite sheets, which were characterized by XRD, SEM, TEM, and tensile and water uptake testing. The resultant nanocomposites showed improved mechanical performance and higher water resistance depending on MWNT size and content. This work details a strategy to achieve improved performance, especially in terms of mechanical properties, using MWNTs of various sizes to regulate the entanglement and penetration between SPI and MWNTs.

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Combining Steric and Electrostatic Stabilization Using Hydrophilic MacroRAFT Agents in an Ab Initio Emulsion Polymerization of Styrene
Authors: dos Santos Amilton Martins , Pohn Jordan , Lansalot Muriel , D'Agosto Franck
Published: June 2007

Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)‐block‐poly(dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electrosterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H+Cl−)‐RAFT and PEO‐RAFT failed to give satisfactory results, PEO‐RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

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New visions in public recreation
Authors: Bellamy George A.
Published: June 2007

A review of the new utterances of various recreational experts, and the stimulating possibilities disclosed by the experience of the War Camp Community Service.
A landlord's encounter with the underworld
Authors: Reynolds James Bronson
Published: June 2007

The author, a leading social worker, was in 1898 on Governor Roosevelt's Tenement‐House Commission which drafted laws defining and extending the responsibilities of landlords in relation to prostitution in tenement houses. He was a member of the staff of the District Attorney of New York County and special counsel to the so‐colled “White Slave Grand Jury,” which returned 26 indictments followed by convictions of offenders against the laws penalizing commercialized vice. He has since been an active leader in the fight against the social evil.
Electric voting in the wisconsin legislature
Authors: Rodriguez Eulogio B.
Published: June 2007

Mr. Rodriguez is one of four graduates of the University of the Philippines who recently were sent to this country for training in legislative and municipal reference library work.
Thermodynamic stability of polyacrylamide and poly(N,N‐dimethyl acrylamide)
Authors: Reber Arthur C. , Khanna Shiv N. , Ottenbrite Raphael
Published: June 2007

Based on theoretical thermodynamic principles, the possibility of environmental degradation of polyacrylamide to its starting monomer was investigated. Theoretical electronic structure studies on the geometry and fragmentation energy of acrylamide and N,N‐dimethyl acrylamide tetramer models were carried out using a first principles gradient corrected density functional approach. Thermal degradation to form a radical would require the cleavage of carbon–carbon bonds in the polymer chain; the energy needed for this cleavage was found to depend on the structure of the repeat unit which ranged from low of 72.5 kcal for a rare head‐to‐head construct to 86.2 kcal for a normal head‐to‐tail polymer construct (therefore, for the cleavage of a normal head‐to‐tail repeat unit, temperatures of approximately 450°C would be required). The thermodynamics of the unzipping, disproportionation, and back‐biting reactions in the resulting radical fragments were also investigated; the back‐biting process was found to require the least energy and provided the most stable radical fragment with a low probability for disproportionation or releasing of monomer to occur. The effect of solvation on the hydrogen‐bonding network in the acrylamide tetramer was studied by adding explicit molecules of water to the tetramer models. The addition of water had a significant effect on the stability of the model polymer slightly stabilizing the head‐to‐head polymer, and slightly destabilizing the head to tail polymer. Copyright © 2007 John Wiley & Sons, Ltd.
Employment status among adult survivors in the Childhood Cancer Survivor Study
Authors: Pang Jenny W.Y. , Friedman Debra L. , Whitton John A. , Stovall Marilyn , Mertens Ann C. , Robison Leslie L. , Weiss Noel S.
Published: June 2007

Background

With increased cure, childhood cancer survivors are reaching adulthood and seeking employment. Host, disease and treatment risk factors may contribute to inability to attain or maintain employment.

Procedure

The prevalence and risk factors for unemployment were evaluated using self‐reported employment history in 10,399 childhood cancer survivors and 3,083 siblings ≥ age 18 in the Childhood Cancer Survivor Study (CCSS).

Results

Among survivors, 5.6% reported unemployment, compared with 1.2% of siblings (odds ratio [OR] 3.7; 95% confidence interval [CI] 2.6, 5.1). Increased risks were observed within all cancer diagnoses. In multivariate analysis, diagnosis of central nervous system (CNS) tumor (OR 1.5; 95% CI 1.1, 2.1), bone cancer (OR 1.5; 95% CI 1.0, 2.1), treatment with ≥30 Gy cranial radiotherapy (OR 4.0; 95% CI 2.9, 5.5), female gender (OR 1.4; 95% CI 1.2, 1.7) and age < 4 years at diagnosis (OR 1.4; 95% CI 1.1, 1.8) increased risk. Diagnosis of CNS or bone tumor or cranial radiotherapy ≥30 Gy remained significant after adjusting for treatment, medical late effects, age and gender. Risk of unemployment decreased with attained age (OR(year) 0.89; 95% CI 0.87, 0.91).

Conclusions

Compared to siblings, adult childhood cancer survivors are at increased risk for unemployment with highest risk defined by diagnosis, treatment and demographic factors. Pediatr Blood Cancer 2008;50:104–110. © 2007 Wiley‐Liss, Inc.
Antidepressant use and off‐label prescribing in children and adolescents in Dutch general practice (2001–2005)
Authors: Volkers Anita C. , Heerdink Eibert R. , van Dijk Liset
Published: June 2007

Purpose

To study the use of antidepressants in children and adolescents in Dutch general practice in 2001 and 2005 and to determine off‐label prescribing.

Methods

Data were obtained from the Netherlands Information Network of General Practice (LINH) that comprised 97 practices in 2001 and 73 practices in 2005. General practitioners (GPs) recorded prescriptions with their indication in the medical records of the patients during one calendar year. We selected boys and girls aged 0–17 years (n = 83 442 in 2001; n = 62 969 in 2005) and identified those who got prescribed antidepressants (N06A). Prevalence of use, indications and percentage of off‐label prescriptions were compared between 2001 and 2005.

Results

The prevalence of selective serotonin reuptake inhibitor (SSRI) use decreased from 1.2 to 1.1 per 1000 children and adolescents between 2001 and 2005. The use of tricyclic antidepressants (TCAs) and other antidepressants also decreased (0.8 to 0.7 and 0.3 to 0.2, respectively). TCAs were often prescribed for nocturnal enuresis, but in patients aged 12–17 years hyperactivity was the leading indication in both years. GPs continued to prescribe SSRIs for depression (about half of the prescriptions) after the safety warnings, while venlafaxine prescribed for depression decreased in favour of anxiety. Off‐label prescribing of SSRIs increased from 16.7% to 34.4% and that of venlafaxine from 22.2% to 58.3%. All SSRI and venlafaxine prescriptions were unlicensed for age.

Conclusions

The decreased use of SSRIs and venlafaxine suggests an impact of the safety warnings. A point of concern is the enlarged off‐label prescribing and insight in the underlying reasons and its appropriateness is needed. Copyright © 2007 John Wiley & Sons, Ltd.
Coronary heart disease outcomes in patients receiving antidiabetic agents
Authors: McAfee Andrew T. , Koro Carol , Landon Joan , Ziyadeh Najat , Walker Alexander M.
Published: June 2007

Background

There is conflicting evidence on the reduction of cardiovascular risk in diabetic patients treated with oral antidiabetic agents.

Objectives

To compare the risk of myocardial infarction (MI) and coronary revascularization (CR) in type 2 diabetic patients treated with rosiglitazone, metformin, or sulfonylurea.

Methods

Using data from a large US insurer, we created propensity‐matched cohorts. We identified hospitalizations for MI or CR. We calculated incidence rates and 95% confidence intervals for the outcomes and estimated risks from Cox proportional hazards models.

Results

We identified 26,931 initiators of monotherapy, 4,086 initiators of dual‐therapy, and 2,346 initiators of combination with insulin therapy. There was no difference between the risk of the composite outcome with rosiglitazone monotherapy compared to metformin monotherapy (HR 1.07, 95% CI: 0.85, 1.34), and similarly with rosiglitazone monotherapy compared to sulfonylurea monotherapy (HR 0.82, 95% CI: 0.67, 1.02). There was no difference in the risk of outcome with rosiglitazone in combination with insulin therapy compared to other oral antidiabetic agents in combination with insulin (HR 0.88, 95% CI: 0.59, 1.32). Overall, there was little difference in the risk of the composite outcome or of the individual outcomes of MI and CR comparing rosiglitazone therapies to non‐rosiglitazone therapies (HR for composite outcome 0.93, 95% CI: 0.80, 1.10).

Conclusions

The results from the monotherapy and the dual‐therapy comparisons, though not individually significant, are consistent in suggesting that the risk of cardiovascular outcome events in patients using rosiglitazone may lie between the risks associated with sulfonylureas (higher incidence) and metformin (lower incidence). Copyright © 2007 John Wiley & Sons, Ltd.
Polymerization of carboxylic ester functionalized norbornenes catalyzed by (η3‐allyl)palladium complexes bearing N‐heterocyclic carbene ligands
Authors: Jung Il Gu , Seo Junhyeok , Chung Young Keun , Shin Dong Mok , Chun Sung‐Ho , Son Seung Uk
Published: June 2007

An in situ generated cationic allylpalladium complex bearing N‐heterocyclic carbene (NHC) ligands, derived from the reaction of [(η3‐C3H5)Pd(NHC)Cl] with AgX (X = BF4 or SbF6), is an active catalyst for the addition polymerization of norbornene and norbornene derivatives [5‐norbornene‐2‐carboxylic acid methyl ester (b) and 5‐norbornene‐2‐carboxylic acid n‐butyl ester (c)] with an ester group containing a large portion of endo‐isomers. The catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polynorbornenes were investigated under various reaction conditions: the catalytic activity was highly dependent on the counteranion, the reaction solvent, and the reaction temperature. For b, as the portion of an endo‐isomer increased, the activity of 13(SbF) was much higher than those of 14 and 15, and for c (exo/endo = 95:5), the maximum turn over number (TON) was observed with 15(SbF). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3042–3052, 2007
Linear viscoelastic behavior of chitosan films as influenced by changes in the biopolymer structure
Authors: da Silva J. A. Lopes , Santos Carla A. N. S.
Published: June 2007

Films were prepared via solvent casting from different deacetylated and depolymerized chitosans obtained from β‐chitin. The linear viscoelastic behavior of the chitosan films was studied with uniaxial tensile stress–relaxation tests. All stress–relaxation profiles exhibited an asymptotically decaying trend, with a residual value different from zero, thus pointing out a solid‐like, viscoelastic behavior. The decay of the tensile modulus with time was phenomenologically described by a generalized Maxwell model consisting of three exponential functions and an equilibrium elastic modulus. Films prepared from chitosans with higher molecular weights showed higher residual elastic moduli and longer relaxation times. Within the range of the degrees of acetylation analyzed (0–27%), chitosans with the lowest and highest degrees of acetylation exhibited more pronounced solid‐like character. This behavior is explained on the basis of a complex balance between steric effects, types of intermolecular interactions, and aggregation of the chitosan samples. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1907–1915, 2007
The effect of nanoparticle shape on polymer‐nanocomposite rheology and tensile strength
Authors: Knauert Scott T. , Douglas Jack F. , Starr Francis W.
Published: June 2007

Nanoparticles can influence the properties of polymer materials by a variety of mechanisms. With fullerene, carbon nanotube, and clay or graphene sheet nanocomposites in mind, we investigate how particle shape influences the melt shear viscosity η and the tensile strength τ, which we determine via molecular dynamics simulations. Our simulations of compact (icosahedral), tube or rod‐like, and sheet‐like model nanoparticles, all at a volume fraction ϕ ≈ 0.05, indicate an order of magnitude increase in the viscosity η relative to the pure melt. This finding evidently can not be explained by continuum hydrodynamics and we provide evidence that the η increase in our model nanocomposites has its origin in chain bridging between the nanoparticles. We find that this increase is the largest for the rod‐like nanoparticles and least for the sheet‐like nanoparticles. Curiously, the enhancements of η and τ exhibit opposite trends with increasing chain length N and with particle shape anisotropy. Evidently, the concept of bridging chains alone cannot account for the increase in τ and we suggest that the deformability or flexibility of the sheet nanoparticles contributes to nanocomposite strength and toughness by reducing the relative value of the Poisson ratio of the composite. The molecular dynamics simulations in the present work focus on the reference case where the modification of the melt structure associated with glass‐formation and entanglement interactions should not be an issue. Since many applications require good particle dispersion, we also focus on the case where the polymer‐particle interactions favor nanoparticle dispersion. Our simulations point to a substantial contribution of nanoparticle shape to both mechanical and processing properties of polymer nanocomposites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1882–1897, 2007
Phase equilibria of polymer dispersed liquid crystal systems in the presence of an external electrical field
Authors: Chen Tao , Zhang Liangshun , Li Tao , Lin Jiaping , Lin Shaoliang
Published: June 2007

The effect of an external electrical field on phase behaviors is reported for polymer dispersed liquid crystal films of 4′‐pentyl‐4‐biphenylcarbonitrile/poly(methyl methacrylate) binary mixtures with various polymer molecular weights. The experimental results show that increasing the molecular weight of the polymer or the electrical field intensity can give rise to an increase in the phase‐transition temperature and a widening of the binary phase region. The lattice theory, regarding a binary system consisting of a rigid nematic liquid crystal and a random polymer, has been extended to the case in which an external electrical field is present. A comparison of the theoretical predictions with the experimental results has been carried out, and satisfactory agreement has been found. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1898–1906, 2007
Molecular modeling of cellulose in amorphous state. III. An innovative elastomeric crosslink system
Authors: Chen Wei , Wang Tao , Lickfield Gary C.
Published: June 2007

The flexibility of molecular structures of rubber materials was evaluated using molecular modeling techniques to develop new crosslink agents which improve deformation recovery of cellulose without significant loss of the mechanical strength. Among the studied structures Poly(propylene oxide) (PPO) pentamer appears to be the most flexible and coiled one. Our calculation results showed that, cellulose crosslinked with PPO pentamers had similar deformation recovery to that crosslinked with DMDHEU. No conformation transitions were observed in these crosslinks when cellulose models were extended to 15% strain, which is consistent with the previous result that conformation transitions in crosslinks should be avoided upon extension to achieve a good recovery on crosslinked cellulose. In addition, PPO crosslinks did not significantly affect the breaking strain of cellulose based upon the cavity volume calculations, and they helped to remove the stress concentration among cellulose chains as suggested by the results of hydrogen bonding analysis. Thus, breaking strength of cellulose might not be significantly affected by PPO crosslinks as well. The preliminary experimental results confirmed above observations. Therefore, PPO pentamer appears to be a promising elastomeric backbone structure of crosslinking agents. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1821–1833, 2007
New classification of supersecondary structures of sandwich‐like proteins uncovers strict patterns of strand assemblage
Authors: Chiang Yih‐Shien , Gelfand Tatiana I. , Kister Alexander E. , Gelfand Israel M.
Published: June 2007

To describe the supersecondary structure (SSS) of β sandwich‐like proteins (SPs), we introduce a structural unit called the “strandon.” A strandon is defined as a set of sequentially consecutive strands connected by hydrogen bonds in 3D structures. Representing β‐proteins as the assembly of strandons exposes the underlying similarities in their SSS and enables us to construct a novel classification scheme of SPs. Classification of all known SPs is based on shared supersecondary structural features and is presented in the SSS database (http://binfs.umdnj.edu/sssdb/). Analysis of the SSS reveals two common specific patterns. The first pattern defines the arrangement of strandons and was found in 95% of all examined SPs. The second pattern establishes the ordering of strands in the protein domain and was observed in 82% of the analyzed SPs. Knowledge of these two patterns that uncover the spatial arrangement of strands will likely prove useful in protein structure prediction. Proteins 2007. © 2007 Wiley‐Liss, Inc.
A tetrapeptide fragment‐based design method results in highly stable artificial proteins
Authors: Dallüge Roman , Oschmann Jan , Birkenmeier Olaf , Lücke Christian , Lilie Hauke , Rudolph Rainer , Lange Christian
Published: June 2007

Computational protein design has progressed rapidly over the last years. A number of design methods have been proposed and tested. In this paper, we report the successful application of a fragment‐based method for protein design. The method uses statistical information on tetrapeptide backbone conformations. The previously published artificial fold of TOP 7 (Kuhlman et al., Science, 2003; 302:1364–1368) was chosen as template. A series of polypeptide sequences were created that were predicted to fold into this target structure. Two of the designed proteins, M5 and M7, were expressed and characterized by fluorescence spectroscopy, circular dichroism and NMR. They showed the hallmarks of well‐ordered tertiary structure as well as cooperative folding/unfolding transitions. Furthermore, the two novel proteins were found to be highly stable against temperature and denaturant‐induced unfolding. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Using layer of protection analysis to define safety integrity level requirements
Authors: Freeman Raymond
Published: June 2007

The recent publication of ANSI/ISA standard S84.01 – 2004 defines the life safety cycle for the design and installation of safety instrumented functions (SIFs) using safety instrumented systems (SISs). However, the determination of the required safety integrity level (SIL) is an activity that the process designers need to complete prior to detailed design. This article outlines an approach for the determination of the required SIL using the layer of protection analysis (LOPA) method. An example is presented along with a suggested format for documenting the LOPA, SIL, and SIF requirements in a manner that can be transferred to the detailed design team for implementation. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2007
Transport of a tripeptide, Gly‐Pro‐Hyp, across the porcine intestinal brush‐border membrane
Authors: Aito‐Inoue Misako , Lackeyram Dale , Fan Ming Z. , Sato Kenji , Mine Yoshinori
Published: June 2007

The transcellular transport of oligopeptides across intestinal epithelial cells has attracted considerable interest in investigations into how biologically active peptides express diverse physiological functions in the body. It has been postulated that the tripeptide, Gly‐Pro‐Hyp, which is frequently found in collagen sequences, exhibits bioactivity. However, the mechanism of uptake of dietary di‐ and tripeptides by intestinal epithelial cells is not well understood. In this study, we used porcine brush‐border membrane (BBM) vesicles to assess Gly‐Pro‐Hyp uptake, because these vesicles can structurally and functionally mimicin vivoconditions of human intestinal apical membranes. The present study demonstrated the time‐dependent degradation of this tripeptide into the free‐form Gly and a dipeptide, Pro‐Hyp, on the apical side of the BBM vesicles. In parallel with the hydrolysis of the tripeptide, the dipeptide Pro‐Hyp was identified in the BBM intravesicular space environment. We found that the transcellular transport of Pro‐Hyp across the BBM was inhibited by the addition of a competitive substrate (Gly‐Pro) for peptide transporter (PEPT1) and was pH‐dependent. These results indicate that Gly‐Pro‐Hyp can be partially hydrolyzed by the brush‐border membrane‐bound aminopeptidase N to remove Gly, and that the resulting Pro‐Hyp is, in part, transported into the small intestinal epithelial cells via the H+‐coupled PEPT1. Gly‐Pro‐Hyp cannot cross the epithelial apical membrane in an intact form, and Pro‐Hyp is highly resistant to hydrolysis by intestinal mucosal apical proteases. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Enumeration of carbohydrate hydroxyl groups by silylation and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Adeuya Anthony , Price Neil P. J.
Published: June 2007

A method for enumerating hydroxyl groups in analytes is described and applied to various carbohydrates. The analytes were derivatized in solution by using trimethylsilylimidazole (TMSI) and the products were analyzed without chromatography by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). The mass spectra revealed consecutive product ion peaks that are separated by 72 m/z units. This 72 m/z unit separation is a result of displacement of a hydroxyl hydrogen atom by a trimethylsilyl group. The number of the observed ions was used to confirm the number of hydroxyl groups in each analyte. This method was utilized in the analysis of single and multi‐component analytes. Published in 2007 by John Wiley & Sons, Ltd.
Nonminimum‐phase output tracking in causal systems using higher‐order sliding modes
Authors: Baev S. , Shtessel Y. , Shkolnikov I.
Published: June 2007

Asymptotic output tracking in a class of causal nonminimum‐phase uncertain nonlinear systems is addressedviahigher‐order sliding modes (HOSMs). Local asymptotic stability of the output‐tracking error dynamics is provided. An output reference profile and an external disturbance forcing the internal dynamics are defined by an unknown linear exosystem. Its characteristic polynomial (which is used in the output‐tracking control algorithm) is identified online by using a HOSM parameter observer. A numerical example illustrates efficiency of the developed HOSM control algorithm. Copyright © 2007 John Wiley & Sons, Ltd.
Residual vibration suppression using Hankel iterative learning control
Authors: van de Wijdeven Jeroen , Bosgra Okko
Published: June 2007

In this paper, we present a new approach for suppression of residual vibrations in point‐to‐point motions based on lifted iterative learning control (ILC). The approach is to add a signal to the command input during the point‐to‐point motion in order to compensate for residual vibrations. A special form of ILC with separate actuation and observation time windows is shown to converge to the required signal. Subsequently, we present ILC control strategies for residual vibration suppression in which convergence and performance specifications can be designed separately. Additionally, the designed controllers have the capability to constrain the amplitude of the command signal. The presented strategies are demonstrated on a flexible system and shown to be successful in the suppression of residual vibration while minimizing the maximum amplitude of the command signal. Copyright © 2007 John Wiley & Sons, Ltd.
A new algorithm for high‐order sliding mode control
Authors: Plestan F. , Glumineau A. , Laghrouche S.
Published: June 2007

A new robust high‐order sliding mode controller for a class of uncertain minimum‐phase single‐input–single‐output (SISO) nonlinear systems is designed. The high‐order sliding mode problem is formulated in input–output term and is viewed in uncertain linear context by considering uncertain nonlinear functions as bounded non‐structured parametric uncertainties. A sliding manifold is designed in order to ensure finite‐time convergence of sliding variable and its high‐order time derivatives. The control law allows the establishment of an rth‐order sliding mode. This result is extended to multi‐input–multi‐output (MIMO) systems. Copyright © 2007 John Wiley & Sons, Ltd.
On the Convergence of Fourier's Method for Nonlinear Wave‐Envelope Equations
Authors: Gajewski Herbert , Zacharias Klaus
Published: June 2007

We consider the initial value problem for a system of nonlinear wave‐envelope equations (Zakharov's system) of one‐dimensional plasma physics in the case of spatially periodic boundary conditions. A regularity property of the solution is shown which allows to prove the convergence of the Fourier approximation method.
Der Satz von Budan ‐ Fourier für allgemeine polynomiale Monosplines
Authors: Stieglitz Michael
Published: June 2007

Ist E = (eϱ) eine Inzidenzmatrix aus 0 und 1 und X eine feste Menge von Knoten χϱ, so gehört zu (E, X) die Menge der allgemeinen polynomialen Monosplines M vom Grad n, M(x):= \documentclass{article}\pagestyle{empty}\begin{document}$ M\left({x} \right)\,: = \frac{{x^n}}{{n!}} + \sum\limits_{v = 0}^{n - 1} {a_v x^v} + \sum\limits_{e_{\rho v} = 1} {a_{\rho v} \left({x - \xi _\rho} \right)_ + ^{n - 1 - v}} $\end{document}. Es wird zunächst eine obere Schranke für die Nullstellen von M im Intervall (0, 1) angegeben. Anwendungen betreffen dann solche Monosplines M, die aus Quadraturformeln entstehen, welche für Polynome vom Höchstgrad n—1 exakt sind. In diesem Fall muß eine zu E gehörige Matrix Ẽ der Pólya‐Bedingung genügen, und M hat im Intervall (0, 1) keine Nullstellen.
Anisotropic Hardening of Initially Orthotropic Materials
Authors: Dafalias Yannis F.
Published: June 2007

A hardening model for an orthotropic material is proposed. The corresponding anisotropic parameters are the components of a fourth order tensor function of the plastic strain, entering a quadratic equation for the yield surface. Assuming polynomial dependence on the plastic strain, the most general form of a polynomial fourth order orthotropic tensor function of a second order symmetric tensor is constructed. This is obtained by imposing on the anisotropic parameters form‐invariance conditions under the orthogonal group of coordinate transformations associated with orthotropic symmetries. This yields the appropriate form of polynomial dependence of these parameters on the corresponding integrity basis. An interesting conclusion is that in addition to the initial orthotropic parameters, new anisotropic parameters appear with plastic strain. Kinematic hardening is also considered. The form‐invariance of the rate constitutive equations is discussed.
Quasioptimalität der Finite‐Elemente‐Methode bei nichtlinearen elliptischen Differentialgleichungen
Authors: Louis A.
Published: June 2007

Quasioptimale Lp‐Fehlerabschätzungen im Sinne von Nitsche [10] werden angegeben für Galerkin‐Lösungen quasilinearer, elliptischer Differentialgleichungen 2m‐ter Ordnung in n Dimensionen. Die approximierenden Teilräume sind Finite‐Elemente‐Räume.
Response of a Single‐mass Vibroimpact System to White‐noise Random Excitation
Authors: Dimentberg M. F. , Menyailov A. I.
Published: June 2007

A simple linear single‐mass oscillator with one or two rigid barriers is considered for the cases of external or parametric white‐noise random excitation. This problem is treated by using a certain piecewise‐differentiable transform of the dependent variable. For the special case of external and elastic impact the solution of the corresponding Fokker‐Planck‐Kolmogorov equation is straightforward, leading to Gaussian and truncated Gaussian stationary distributions of the velocity and displacement respectively. The general case is treated in “quasiconservative” approximation by averaging energy. This leads to a first‐oder stochastic equation for the energy and to a closed‐form solution for the stationary probability density p(E). In the case of parametric excitation necessary and sufficient conditions for the existence of p(E) are obtained.
Über ein System linearer Funktional‐Differentialgleichungen
Authors: Vogl F.
Published: June 2007

In der Arbeit werden Systeme linearer Funktional‐Differentialgleichungen der Form y′ (x) = Ay(λx), 0 < λ < 1, unter‐sucht. Die Elemente ajk der Matrix A sind komplexe Konstante, während die Variable x reell oder komplex sein kann. Vorerst wird die Struktur aller ganzen Lösungen angegeben. Anschließend wird für x ≠ 0 ein System spezieller analytischer Lösungen konstruiert, mit dessen Hilfe alle weiteren Lösungen dargestellt werden können. Außerdem werden die asymptotischen Eigenschaften (für x → ∞) aller Lösungen diskutiert, und es wird gezeigt, daß jeweils genau eine Lösung mit einem bestimmten, geeignet vorgegebenen asymptotischen Verhalten existiert.
Geschwindigkeits‐ und Temperaturverteilung in Hamelscher Spiralströmung
Authors: Schobeiri M. Taher
Published: June 2007

Für die Hamelsche Spiralströmung wurde die Temperaturverteilung angegeben. Nach der Ermittlung der Geschwindigkeitsverteilung konnte die partielle Differentialgleichung der Energie mittels eines Separationsansatzes in eine gewöhnliche Differentialgleichung überführt werden. Für alle Sonderfälle dieser Differentialgleichung konnten numerische Lösungen angegeben werden.
Numerische Auswertung von Berechnungsformeln für Überschreitenswahrscheinlichkeiten stochastisch beanspruchter mechanischer Systeme
Authors: Friedrich H. , Hennig K.
Published: June 2007

Bei der Behandlung von stochastisch beanspruchten Konstruktionen hat die Berechnung der Überschreitenswahrscheinlichkeit – das ist die Wahrscheinlichkeit dafür, daß ein betrachteter stochastischer Prozeß in einem bestimmten Zeitintervall ein vorgegebenes Sicherheitsniveau mindestens einmal überschreitet – große praktische Bedeutung. Es wird auf die numerische Auswertung früher hergeleiteter Berechnungsformeln und einige Anwendungsbeispiele ein‐gegangen.
Modale und integrale Kovarianzanalyse hybrider Systeme
Authors: Wedig W.
Published: June 2007

Am Beispiel einer vorgespannten Saite unter sowohl örtlich als auch zeitlich unkorrelierter Zufallserregung werden modale und integrale Kovarianzanalysen bei sogenannten hybriden Systemen erklärt. Diese Systeme können zwar noch selbstadjungiert sein; sie besitzen aber infolge der in den Randbedingungen enthaltenen Zeitableitungen nicht mehr die klassische Orthogonalitätseigenschaft. Es wird gezeigt, daß die geschlossen angebbaren Kovarianzlösungen der Integralanalysis mit den Reihenentwicklungen einer verallgemeinerten Modalanalysis übereinstimmen.
Analytizitätseigenschaften der Lösungen nichtlinearer Operatorgleichungen vom Hammerstein‐Typ und rekursive Bestimmung ihrer Lösung
Authors: Marx B. , Vogel J.
Published: June 2007

In dieser Arbeit wird für den Verzweigungsfall bei Hammersteinschen Operatorgleichungen eine Variante zur Gewinnung eines der Ausgangsgleichung äquivalenten Gleichungssystems dargelegt. Zwei Sätze über die Auflösung der zum System gehörenden Operatorgleichung werden bewiesen, die unter Analytizitätsvoraussetzungen an den nichtlinearen Operator in der Ausgangsgleichung Analytizität der Lösung bringen. Außerdem wird eine Rekursionsformel für die Koeffizienten der Lösung der lokal eindeutig auflösbaren Operatorgleichung entwickelt. Diese Rekursion wird auf die Koeffizientenfunktionen des Systems der Verzweigungsgleichungen unter Berücksichtigung der Eigenschaften des nichtlinearen Operators übertragen.
Statistische Rißausbreitung in eindimensionalen Systemen ohne Wechselwirkung
Authors: Schultrich B. , Posselt M.
Published: June 2007

Die Bruchstatistik berücksichtigt den Einfluß der lokalen Festigkeitsschwankungen auf die Entwicklung der Vorschädigung und deren Übergang in den makroskopischen Bruch. Die hierzu gewöhnlich benutzte Einzelrißnäherung wird an einem eindimensionalen Modellsystem aus nicht miteinander wechselwirkenden Elementen getestet. Für die offene und die geschlossene Elementekette werden Mittelwert und Schwankung der Rißlängenverteilung sowie die makroskopische Bruchwahrscheinlichkeit berechnet. Die Näherungsbeziehungen lassen sich hieraus als asymptotischer Grenzfall für große Systeme gewinnen. Die Rolle der Randeffekte und der statistischen Korrelationen, in deren Vernachlässigung die Einzelrißnäherung besteht, wird genauer untersucht.
Free and Forced Vibrations of a Linear Non‐Conservative System with Multiple Eigenvalues
Authors: Kliem W.
Published: June 2007

The paper shows the derivation of the response of a linear system governed by the equation A\documentclass{article}\pagestyle{empty}\begin{document}$ \ddot q $\end{document} + Bq̇ + Cq = Q(t), in which the square matrices A, B and C are real and constant, but not necessary symmetric or positive definite. In addition the special case of multiple eigenvalues with an insufficient number of eigenvectors occurs. The theory is an extension of the work by Wahed and Bishop [1], which is limited to distinct eigenvalues.
Error Propagations in Implicit Discretized Viscous Flow Models
Authors: Dey S. K.
Published: June 2007

It has been claimed in general, that implicit finite difference solution of Navier‐Stokes' equations is unconditionally stable. A linearized stability analysis [1] showed that if finite difference representations of boundary conditions do not contain errors and if truncations errors are neglected, such a claim is justifiable. However, in most problems, boundary conditions are often approximated and hence errors originate from there. Furthermore, depending upon the flow conditions and input parameters (like time steps, mesh sizes), truncation errors may have significant contributions upon numerical solutions. In this paper these investigations have been made.
Convergence of Sequences of Linear Functionals
Authors: Jim Pozo M. A. Énez
Published: June 2007

The aim of this paper is to complete the theory of some qualitative and quantitative theorems of Korovkin's type in spaces of continuous functions when the limit linear functional (or operator) is not the identity and the considered linear functionals (or operators) are not necessarily positive.
Biological vs. Chemical evaluation of toxicity and protein quality of cottonseed meals
Authors: Eagle Edward , Blalek H. F. , Davies D. L. , Bremer J. W.
Published: June 2007

Toxicological evaluation of 68 cottonseed meals in rats failed to show a direct correlation between their toxicity and their free, total or combined gossypol content. The common practice of considering the free gossypol content of cottonseed meal as a yardstick for its toxicity is questioned.

There was poor correlation between biologically evaluated protein quality of cottonseed meals and their nitrogen solubility in 0.02N sodium hydroxide. Application of this chemical test for indicating the protein quality of cottonseed meals is likewise questioned on the basis of existing evidence.