bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of pH on Inactivation of Escherichia coli K12 by Sonication, Manosonication, Thermosonication, and Manothermosonication
Authors: Lee H. , Zhou B. , Feng H. , Martin S.E.
Published: April 2009

ABSTRACT:  The effect of pH on inactivation of Escherichia coli K12 by sonication at 100 kPa/40 °C, manosonication (MS) at 400 kPa/40 °C, thermosonication (TS) at 100 kPa/61 °C, and manothermosonication (MTS) at 400 kPa/61 °C at acoustic energy density of 3 W/mL and 6 W/mL was investigated. Five linear and nonlinear kinetic models were used to examine the inactivation kinetics. At all pH levels, the inactivation rates of E. coli K12 in a buffer by TS and MTS were significantly higher than those by sonication and MS. A 5 log reduction of E. coli K12 population by TS and MTS was achieved in 0.5 and 0.25 min, respectively. With an initial count of 108 CFU/mL, no colonies were detected at pH 3 after a 0.25‐min MTS treatment. The lethal effect of MTS was enhanced at low pH (pHs 3 and 4), whereas at nonlethal temperature of 40 °C, no increased killing was observed. Regardless of pH, the treatment by MTS, TS, and MS exhibited a rapid initial reduction followed by tailing‐off on the inactivation curves. The biphasic linear, log‐logistic, and modified Gompertz kinetic models allowed better fitting of the inactivation data for MTS, TS, and MS treatments than the 1st‐order and Weibull models. The survival counts of sonication‐treated E. coli K12 at all pH levels fitted well to a 1st‐order kinetic model.
Quantification of Almond Skin Polyphenols by Liquid Chromatography‐Mass Spectrometry
Authors: Bolling Bradley W. , Dolnikowski Gregory , Blumberg Jeffrey B. , Oliver Chen C.Y.
Published: April 2009

ABSTRACT:  Reverse phase HPLC coupled to negative mode electrospray ionization (ESI) mass spectrometry (MS) was used to quantify 16 flavonoids and 2 phenolic acids from almond skin extracts. Calibration curves of standard compounds were run daily and daidzein was used as an internal standard. The inter‐day relative standard deviation (RSD) of standard curve slopes ranged from 13% to 25% of the mean. On column (OC) limits of detection (LOD) for polyphenols ranged from 0.013 to 1.4 pmol, and flavonoid glycosides had a 7‐fold greater sensitivity than aglycones. Limits of quantification were 0.043 to 2.7 pmol OC, with a mean of 0.58 pmol flavonoid OC. Mean inter‐day RSD of polyphenols in almond skin extract was 6.8% with a range of 4% to 11%, and intra‐day RSD was 2.4%. Liquid nitrogen (LN2) or hot water (HW) blanching was used to facilitate removal of the almond skins prior to extraction using assisted solvent extraction (ASE) or steeping with acidified aqueous methanol. Recovery of polyphenols was greatest in HW blanched almond extracts with a mean value of 2.1 mg/g skin. ASE and steeping extracted equivalent polyphenols, although ASE of LN2 blanched skins yielded 52% more aglycones and 23% less flavonoid glycosides. However, the extraction methods did not alter flavonoid profile of HW blanched almond skins. The recovery of polyphenolic components that were spiked into almond skins before the steeping extraction was 97% on a mass basis. This LC‐MS method presents a reliable means of quantifying almond polyphenols.
Purification and Use of Glycomacropeptide for Nutritional Management of Phenylketonuria
Authors: LaClair Caitlin E. , Ney Denise M. , MacLeod Erin L. , Etzel Mark R.
Published: April 2009

ABSTRACT:  Individuals with phenylketonuria (PKU) cannot metabolize phenylalanine (Phe) and must adhere to a low‐Phe diet in which most dietary protein is provided by a Phe‐free amino acid formula. Glycomacropeptide (GMP) is the only naturally occurring protein that does not contain Phe, and is of interest as a source of protein for dietary management of PKU. However, commercially available GMP contains too much Phe from residual whey proteins and does not contain adequate levels of all the indispensable amino acids to provide a nutritionally complete protein. The aim of this study was to increase purity of GMP and develop a mass balance calculation for indispensable amino acid supplementation of GMP foods. Cation exchange chromatography, ultrafiltration/diafiltration, and lyophilization were used at the pilot plant scale to decrease Phe. Enough purified GMP (5 kg) was manufactured to provide 15 PKU subjects with a 4‐d diet in which the majority of protein was from GMP foods. A mass balance was used to supplement GMP foods so that all indispensable amino acids met or exceeded the daily recommended intake. GMP foods were tested in a human clinical trial as a replacement for the traditional amino acid formula. Nutritionally complete GMP foods created with high purity GMP provide individuals with PKU with more options to manage PKU, which may lead to improved compliance and quality of life.
Fed State Protein Turnover in Healthy Older Persons under a Usual Protein‐Rich Diet
Authors: Pfrimer Karina , Marchini Julio Sergio , Moriguti Julio Cesar , Ferriolli Eduardo
Published: April 2009

ABSTRACT:  The objective of this study was to verify the protein turnover rates of healthy older persons under a usual protein‐rich diet and to compare values to those described in the literature. This cross‐sectional study was conducted at Metabolism Unit, Univ. Hospital of the School of Medicine of Ribeirao Preto, Univ. of Sao Paulo, Brazil. In this study, 7 healthy older persons aged 65.4 ± 2.8 y, with BMI 22.7 ± 2.4 kg/m2 and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9‐h whole‐body 15N‐glycine single‐dose study was performed after an overnight fast. During the study, each subject received 6 isoenergetic, isonitrogenous meals at 2‐h intervals based on their average intake. Ammonium, urea, and total nitrogen were quantified and analyzed by mass spectrometry, with the determination of total protein turnover rates by the 15N‐glycine method. The results show that total nitrogen output was 3.2 ± 0.96 g/N and intake 7.7 ± 1 g/N, 15N nitrogen flux was 30.6 ± 6.3 g/9 h. Endogenous nitrogen balance was positive (4.5 g ± 1 g/N in 9 h). In conclusion, the protein turnover of healthy older persons under a usual protein‐rich diet is positive during the fed state and has synthesis and degradation rates similar to those previously described in studies involving diet adaptation periods.
Isolation and Identification of Antihypertensive Peptides from Antarctic Krill Tail Meat Hydrolysate
Authors: Hatanaka Akimasa , Miyahara Hiroko , Suzuki Ken Ichi , Sato Seizo
Published: April 2009

ABSTRACT:  Antarctic krill (Euphausia superba) obtained from the huge biomass in Antarctic waters is an important food product in Japan. Antarctic krill peptide powder (AKPP) prepared from the tail meat by enzymatic hydrolysis significantly decreased the systolic blood pressure in spontaneously hypertensive rats by a single oral administration (1, 10, or 100 mg). Presumably, the effect of AKPP was through inhibition of the conversion of angiotensin, which mediates blood pressure elevation, from its inactive propeptide to the mature angiotensin. Two potent angiotensin I‐converting enzyme (ACE) inhibitory peptides were isolated from AKPP by high‐performance liquid chromatography (HPLC) and identified as Val‐Trp (IC50= 2.75 μg/mL; 12.9 μM) and Leu‐Lys‐Tyr (IC50= 4.26 μg/mL; 10.1 μM). Val‐Trp and Leu‐Lys‐Tyr comprised 0.025%± 0.0023% (w/w) and 0.018%± 0.0023% (w/w) of AKPP, respectively, as measured by electrospray ionization mass spectrometry (ESI‐MS). The contributions of Val‐Trp and Leu‐Lys‐Tyr to the ACE inhibitor activity of AKPP were 17.7%± 1.60% and 8.04%± 1.03%, respectively, suggesting that these 2 peptides constitute a substantial portion of the overall ACE inhibitor potential of AKPP.
Synergistic Effect of Electrolyzed Water and Citric Acid Against Bacillus Cereus Cells and Spores on Cereal Grains
Authors: Park Young Bae , Guo Jin Yong , Rahman S.M.E. , Ahn Juhee , Oh Deog‐Hwan
Published: April 2009

ABSTRACT:  The effects of acidic electrolyzed water (AcEW), alkaline electrolyzed water (AlEW), 100 ppm sodium hypochlorite (NaClO), and 1% citric acid (CA) alone, and combinations of AcEW with 1% CA (AcEW + CA) and AlEW with 1% CA (AlEW + CA) against Bacillus cereus vegetative cells and spores was evaluated as a function of temperature (25, 30, 40, 50, or 60 °C) and dipping time (3 or 6 h). A 3‐strain cocktail of Bacillus cereus cells or spores of approximately 107 CFU/g was inoculated in various cereal grains (brown rice, Job's tear rice, glutinous rice, and barley rice). B. cereus vegetative cells and spores were more rapidly inactivated at 40 °C than at 25 °C. Regardless of the dipping time, all treatments reduced the numbers of B. cereus vegetative cells and spore by more than 1 log CFU/g, except the deionized water (DIW), which showed approximately 0.7 log reduction. The reductions of B. cereus cells increased with increasing dipping temperature (25 to 60 °C). B. cereus vegetative cells were much more sensitive to the combined treatments than spores. The effectiveness of the combined electrolyzed water (EW) and 1% CA was considerable in inhibiting B. cereus on cereal grains. The application of combined EW and CA for controlling B. cereus cells and spores on cereal grains has not been previously reported. Therefore, the synergistic effect of EW and CA may provide a valuable insight on reducing foodborne pathogens on fruits, vegetables, and cereal grains.
Rheological and Microstructural Properties of Porcine Myofibrillar Protein–Lipid Emulsion Composite Gels
Authors: Wu Mangang , Xiong Youling L. , Chen Jie , Tang Xueyan , Zhou Guanghong
Published: April 2009

ABSTRACT:  The objective of the study was to investigate the role of emulsified fat (lard) and oil (peanut oil) in the rheology and microstructure of porcine myofibrillar protein (MP) gels. Heat‐induced composite gels were prepared from 2% MP with 0% to 15% pre‐emulsified lipids at 0.6 M NaCl, pH 6.2. Dynamic rheological testing upon temperature sweeping (20 to 80 °C at 2 °C/min) showed substantial increases in G′ (an elastic modulus) of MP sols/gels with the addition of emulsions. Gel hardness was markedly enhanced (P < 0.05) by incorporating ≥10% emulsions, and the composite gel with 15% lard was 33% more rigid (P < 0.05) than that with 15% peanut oil. Incorporation of both emulsions at 10% or higher levels improved the water holding capacity of the gels by 28% to 44% (P < 0.05). Light microscopy revealed a compact gel structure filled with protein‐coated fat/oil globules that interacted with the protein matrix via disulfide bonds. The results indicated that both physical and chemical forces contributed to the enhancements in the rheology, moisture retention, and lipid stabilization in the MP–emulsion composite gels.
Irradiation Treatments to Improve the Shelf Life of Fresh Black Truffles (Truffles Preservation by Gamma‐Rays)
Authors: Reale Anna , Sorrentino Elena , Iacumin Lucilla , Tremonte Patrizio , Manzano Marisa , Maiuro Lucia , Comi Giuseppe , Coppola Raffaele , Succi Mariantonietta
Published: April 2009

ABSTRACT:  The aim of this study was to individuate a method to improve the shelf life of fresh truffles, hypogeous fungi highly prized but very perishable as well. Microbial ecology of fresh products was investigated and the effect of irradiation at different doses on microbial and sensorial parameters was assayed. Data showed that fresh truffles are strongly contaminated from different groups of microorganisms. Irradiation was able to influence their growth, determining an impressive reduction. Treatments at 5 and 10 kGy doses produced the highest microbial decontamination but negatively influenced sensorial parameters. Irradiation at a 1.5 kGy dose was the best solution to improve the shelf life of truffles.
Persistent Organic Pollutants in Fish Oil Supplements on the Canadian Market: Polychlorinated Dibenzo‐p‐Dioxins, Dibenzofurans, and Polybrominated Diphenyl Ethers
Authors: Rawn D.F.K. , Breakell K. , Verigin V. , Nicolidakis H. , Sit D. , Feeley M. , Ryan J.J.
Published: April 2009

ABSTRACT:  Canadians are interested in improving their diet through the consumption of fish oil food supplements, which are marketed to be rich in omega‐3 fatty acids. Convenience samples of omega‐3 enriched dietary supplements (n = 30) were collected in Vancouver, Canada, between 2005 and 2007. All of the omega‐3 supplements were analyzed for polychlorinated dibenzo‐p‐dioxins/furans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs) and, although every sample was found to contain detectable residues of PBDEs, only 24 samples were found to have PCDD/F concentrations above the level of detection. PCDD/F concentrations ranged from 0.05 pg TEQ/g lipid to 45.7 pg TEQ/g lipid in salmon and shark oils, respectively. Maximum PBDE concentrations similarly were observed in shark oil (113 μg/kg lipid), however, most supplements had concentrations below 5 μg/kg lipid. Average PCDD/F and PBDE intake estimates, based on consumption of maximum supplement dose following product label recommendations, were 4.32 pg TEQ/d and 25.1 ng/d lipid, respectively.
The Pursuit of Postsecondary Education: A Comparison of First Nations, African, Asian, and European Canadian Youth*
Authors: THIESSEN VICTOR
Published: April 2009

Utilisant l'Enquête auprès des jeunes en transition (EJET), sondage longitudinal nationalement représentatif, l'auteur examine l'argument voulant que les résultats éducationnels inférieurs de diverses minorités visibles et d'immigrants seraient attribués à leurs désavantages socioéconomiques, tandis que les résultats supérieurs des autres minorités visibles auraient pour cause leur soutien culturel. Les analyses rapportent des inégalités non négligeables dans le parcours pédagogique des Premières nations, des minorités visibles et des immigrants. Cependant, ni leur emplacement structurel ni leurs attributs culturels (ni les deux ensemble) n'expliquent entièrement les différences de leur parcours pédagogique ni ne peuvent être réduits à un simple modèle dans lequel les désavantages structurels détermineraient les résultats inférieurs et les facteurs culturels les supérieurs.

Using the nationally representative longitudinal Youth in Transition Survey, this paper examines the argument that inferior educational outcomes of various visible minorities and immigrants can be attributed to their socio‐economic disadvantages, while superior outcomes of other visible minorities is due to their cultural supports. The analyses document sizeable inequalities in educational pathways of First Nations, visible minorities, and immigrants. However, neither structural location nor cultural attributes (nor both in conjunction) totally account for differences in their educational pathways nor can they be reduced to a simple pattern whereby structural disadvantages account for inferior pathways and cultural factors for superior ones.
Optimal Ordering Policies for Stochastic Inventory Problems with Observed Information Delays
Authors: Bensoussan Alain , Çakanyιldιrιm Metin , Feng Qi , Sethi Suresh P.
Published: April 2009

Information delays exist in an inventory system when it takes time to collect, process, validate, and transmit inventory/demand data. A general framework is developed in this paper to describe information flows in an inventory system with information delays. We characterize the sufficient statistics for making optimal decisions. When the ordering cost is linear, the optimality of a state‐dependent base‐stock policy is established even when information flows are allowed to cross over time. Additional insights into the problem are obtained via a comparison between our models and the models with stochastic order lead times. We also show that inventory can substitute for information and vice versa.
Optimal Pricing and Rebate Strategies in a Two‐Level Supply Chain
Authors: Cho Soo‐Haeng , McCardle Kevin F. , Tang Christopher S.
Published: April 2009

For many product categories, manufacturers and retailers often offer rebates to stimulate sales. Due to certain adverse effects, however, some manufacturers and retailers are contemplating the elimination of their rebate programs. This paper sheds light on the debate about the value of rebate programs by presenting a model for evaluating the conditions under which a firm should offer rebates in a competitive environment. Specifically, we consider a two‐level supply chain comprising one manufacturer and one retailer. Each firm makes three decisions: the regular (wholesale or retail) price, whether or not to offer rebates, and the rebate value should the firm decide to launch a rebate program. We determine the equilibrium of a vertical competition game between the manufacturer (leader) and the retailer (follower), and we provide insights about how competition affects the conditions under which a firm should offer rebates in equilibrium.
Channel Strategies for Durable Goods: Coexistence of Selling and Leasing to Individual and Corporate Consumers
Authors: Tilson Vera , Wang Yunzeng , Yang Wei
Published: April 2009

In durable goods markets, such as those for automobiles or computers, the coexistence of selling and leasing is common as is the existence of both corporate and individual consumers. Leases to corporate consumers affect the price of used goods on the second‐hand market which in turn affect the buying and leasing behavior of individual consumers. The setting of prices (or volumes) for sale and lease to individual and corporate consumers is a complicated problem for manufacturers. We consider a manufacturer who concurrently sells and leases a finitely durable good to both individual and corporate consumers. The interaction between the manufacturer and consumers is modeled as a dynamic sequential game, where each player seeks to maximize its own payoff over an infinite horizon. We study how the corporate channel substitutability of new goods and used goods and transaction costs in the second‐hand market affect the manufacturer's pricing decisions, consumer behavior, and social welfare in the retail market. Making a number of simplifying assumptions, including two‐period lifetime for the finitely durable goods, we consider Markov Perfect Equilibrium as the solution concept. We show that the manufacturer can maximize her profit by segmenting consumers according to their willingness to pay. Selling and leasing are the mechanisms used for price discrimination in the retail market. We show that as she leases a larger share of her production to the corporate consumer, (1) the manufacturer does not necessarily have to adjust the optimal selling price of new goods to individual consumers, and the volume of sales of new goods to individual consumers can stay the same; (2) the manufacturer does increase the retail lease price, and the number of individual leases decreases; (3) the net supply of used goods on the market increases, leading to a lower market price for used goods; and (4) more individual consumers are able to participate in the market, and their collective welfare or net utility improves. We also show that as production costs increase the manufacturer increases prices, reducing volumes across all channels. When transaction costs increase, the manufacturer reduces leasing in both corporate and retail channels.
How Plant Managers' Experiences and Attitudes Toward Sustainability Relate to Operational Performance
Authors: Pagell Mark , Gobeli David
Published: April 2009

Managers are increasingly faced with pressure to think not just about profits, but also about their organization's environmental and social performance. This research provides a first examination of operational managers' experiences with and attitudes about employee well‐being and environmental issues, how these factors impact employee well‐being and environmental performance, and how the three performance measures interrelate. We use violations of Occupational Safety and Health Administration regulations and Toxic Release Inventory reports of emissions as proxies for employee well‐being and environmental performance. Our findings suggest that operational managers do not (yet) think in sustainability terms. However, employee well‐being and environmental performance do interact in a significant way with operational performance. Hence, operational managers would benefit from a more complete understanding of the relationships among the elements of the triple bottom line.
Mechanics and Computational Models for Laminated Piezoelectric Beams, Plates, and Shells
Authors: Saravanos Dimitris A. , Heyliger Paul R.
Published: April 2009

A considerable number of laminate theories, analytical approaches, numerical solutions and computational models have been reported for the analysis of laminates and structures with piezoelectric actuators or sensors. This article provides a review of published work in this area of mechanics. The reported laminate theories and structural mechanics are classified based on fundamental assumptions, the approximation of the through-the-thickness variation of the electromechanical state variables, the method of representation of piezoelectric layers, and their capability to model curvilinear geometries and thermal effects. The performance, advantages and limitations of the various categories of laminate theories are subsequently assessed by correlating results obtained by representative average models. The capability of each theory to model global structural response, local through-the-thickness variations of electromechanical variables, stresses, and piezoelectric laminates of high thickness is also quantified. This review article includes 103 references.
Review of Nonlinear Panel Flutter at Supersonic and Hypersonic Speeds
Authors: Mei Chuh , Abdel-Motagaly K. , Chen R.
Published: April 2009

A review of various analytical methods and experimental results of supersonic and hypersonic panel flutter is presented. The analytical methods are categorized into two main methods. The first category is the classical methods, which include Galerkin in conjunction with numerical integration, harmonic balance and perturbation methods. The second category is the finite element methods in either the frequency domain (eigensolution) or the time domain (numerical integration). A review of the experimental literature is given. The effects of different parameters on the flutter behavior are described. The parameters considered include inplane forces, thermal loading, flow direction, and initial curvature. Active control of composite panels at supersonic speeds and elevated temperatures is also considered. This review article cites 84 references.
Composite Materials and Structures: Science, Technology and Applications - A Compendium of Books, Review Papers, and Other Sources of Information
Authors: Bogdanovich Alexander E. , Sierakowski Robert L.
Published: April 2009

A fast growing volume of literature in various fields of composite materials and structures has inspired the authors to attempt to assemble all major books and review papers in a concise compendium presented here. This could give researchers, engineers, designers, and graduate students a rapid access to the vast volume of references on any specific topic in the field of composites and thereby satisfy their research requirements. The compendium includes encyclopedias, handbooks, design guides, textbooks, reference books, review papers and also a few collections of papers. The topics span theory, modeling and analysis of composite materials, processing and manufacturing, properties and characterization, theory and analysis of composite structures, joints and connections, designing with composites, and composites applications. The compendium includes over 400 references, which are arranged in alphabetical order within each topic under consideration. Additionally, the reader can find, in this compendium, the lists of major conferences, journals, and ASTM STP publications on composites. The major objective of this work is not critically reviewing or discussing specific research approaches and results. The authors have rather intended to provide extensive bibliographic information that may help the reader to get familiar with the primary literature and, if necessary, undertake further literature search on any particular problem of interest.
Review of Dual Boundary Element Methods With Emphasis on Hypersingular Integrals and Divergent Series
Authors: Chen J. T. , Hong H.-K.
Published: April 2009

This article provides a perspective on the current status of the formulations of dual boundary element methods with emphasis on the regularizations of hypersingular integrals and divergent series. A simple example is given to show the dual integral representation and the dual series representation for a discontinuous function and its derivative and thereby to illustrate the regularization problems encountered in dual boundary element methods. Hypersingularity and the theory of divergent series are put under the framework of the dual representations, their relation and regularization techniques being examined. Applications of the dual boundary element methods using hypersingularity and divergent series are explored. This review article contains 249 references.
Interaction of Waves in Solid Mixtures
Authors: Rushchitsky J. J.
Published: April 2009

The focus of this review article is on analytical procedures and physical effects which are characteristic of the theory of nonlinear and simple waves in materials. Waves are supposed to propagate in composite materials, which are modeled as solid two-phase mixtures. It is shown how procedures of wave interaction investigations in nonlinear acoustics, optics and radiophysics are applied to nonlinear mechanics of materials with a microstructure. Main effects of the interactions of waves in composite materials: new harmonics generation, self-generation, evolution and distortion, synchronization, breakdown instability, etc are commented upon. This article is proposed not only for specialists in wave theories; therefore it contains some facts which are obvious for researchers working in the field of waves. Many portions of this review are described in more detail in a book (Rushchitsky and Tsurpal (1998), 377 pages). This review article contains 286 references.
Multidimensional Modeling of Impinging Sprays on the Wall in Diesel Engines
Authors: Senda J. , Fujimoto H. G.
Published: April 2009

This article summarizes model analysis of the dispersion process of a Diesel spray on the wall surface in order to simulate the spray-wall interaction process in Diesel engines. The mixture formation process near the wall of the piston cavity affects the combustion process and the hydrocarbon or soot formation process through the quenching of the mixture and flame at the wall surface. In particular, mixture burning occurs mainly near the cavity wall through the whole combustion period in the case of high pressure fuel injection. In this article, representative modeling approaches on spray-wall interaction process including the film flow formation are summarized briefly. Then, our models of spray impingement for low/high-temperature models including the process of fuel film formation, film breakup, wall-drop/film heat transfer, and droplet breakup owing to the solid-liquid interface boiling are introduced with the comparison of experimental results. This review article includes 83 references.
Optimization of Structures in Unilateral Contact
Authors: Hilding D. , Klarbring A. , Petersson J.
Published: April 2009

This article gives a review of optimization of structures in mechanical contact. Emphasis is put on linear elastic structures in frictionless contact. In particular, for optimization problems where an energy objective is used, a unified framework is given in parallel with the review. Papers related to optimal control of variational inequalities or dealing with pure sensitivity analysis are treated in less detail. Problems involving friction are also reviewed at a less detailed level. It is explained why structural optimization problems involving contact cannot be treated within classical smooth optimization theory and how they relate to modern fields such as nonsmooth optimization and mathematical programs with equilibrium constraints (MPECs). Throughout the article, discrete and continuous problems are treated in parallel. This review article includes 106 references.
Progress in Structural Dynamics With Stochastic Parameter Variations: 1987-1998
Authors: Manohar C. S. , Ibrahim R. A.
Published: April 2009

This article is an update of an earlier paper by Ibrahim (1987) and is aimed at reviewing the work published during the last decade in the area of vibration of structures with parameter uncertainties. Different types of uncertainty modeling are described in terms of material and geometric properties. These models are considered in terms of Gaussian or non-Gaussian distributions. Computational stochastic algorithms including stochastic finite element methods and Monte Carlo simulation are dominating a major part of current activities. Recent analytical developments of the random eigenvalue problem are reviewed with reference to typical structural elements. These developments include the implementation of statistical energy analysis, stochastic boundary element methods, and interval algebra. Other topics include forced vibration of single- and multi-degree-of-freedom systems including nonlinear systems, localization in disordered periodic structures, and experimental results. Computational stochastic mechanics has found several industrial applications including aerospace, automotive and composite structural elements. The review also covers developments in the areas of statistical modeling of high frequency vibrations. There are 183 references.
Influence of Loading Rate on the Interlaminar Fracture Properties of High Performance Composites - A Review
Authors: Cantwell W. J. , Blyton M.
Published: April 2009

A number of workers have investigated the effect of varying loading rate on the interlaminar fracture properties of fibre reinforced composite materials. In spite of such efforts, a study of the published literature indicates that considerable disagreement still exists and a clear understanding of this highly important issue has yet to be achieved. This review article summarises many of the reported findings and attempts to explain some of the anomalies reported in the literature. This review article contains 58 references.
On the Dynamics of Elastic Multibody Systems
Authors: Bremer Hartmut
Published: April 2009

Due to the highly complex structure of the equations of motion, there exists a basic demand for procedures with minimum effort. This is achieved by the projection method applied to systems consisting of rigid and elastic bodies which undergo fast rigid body motions with superimposed small elastic deflections. The outlined method leads to different left and right Jacobians for the partial differential equations along with simple operators for determination of corresponding boundary conditions. When a Ritz series expansion is used for approximate solution, the left and right Jacobians become identical. The procedure is demonstrated for plate vibrations without rigid body motion and then applied to a single moving beam and finally augmented to multi beam systems. Special attention is hereby given to the effects of dynamical coupling which influence bending stiffness and connect bending with torsion. This review article has 55 references.
Mass versus relativistic and rest masses
Authors: Okun L. B.
Published: April 2009

The concept of relativistic mass, which increases with velocity, is not compatible with the standard language of relativity theory and impedes the understanding and learning of the theory by beginners. The same difficulty occurs with the term rest mass. To get rid of relativistic mass and rest mass it is appropriate to replace the equation E=mc2 by the true Einstein’s equation E0=mc2, where E0 is the rest energy and m is the mass.
Momentum-energy change in elastic relativistic binary collisions
Authors: Menon V. J. , Dubey R. K. , Mishra M. , Patra B. K.
Published: April 2009

We consider a relativistic elastic collision between a projectile of momentum p with a target atom of momentum k in a general inertial frame. We employ one space plus one time Minkowski geometry and calculate the momentum transfer vector qμ suffered by the projectile calculated via a Lorentz transformation to the barycentric frame and then eliminate k. The resulting expression for qμ reproduces several known cases, its algebraic behavior can be interpreted physically, and it leads to a simple understanding of the relativistic equipartition law.
Three-vector and scalar field identities and uniqueness theorems in Euclidean and Minkowski spaces
Authors: Woodside Dale A.
Published: April 2009

Euclidean three-space and Minkowski four-space identities and uniqueness theorems are reviewed and extended. A Helmholtz identity is used to prove two three-vector uniqueness theorems in Euclidean three-space. The first theorem specifies the divergence and curl of the vector, and the second is a Helmholtz type theorem that sums the irrotational and solenoidal parts of the vector. The second theorem is shown to be valid for three-vector fields that are time dependent. A time-dependent extension of the Helmholtz identity is also derived. However, only the three-vector and scalar components of a Minkowski space four-vector identity are shown to yield two identities that lead to a uniqueness theorem of the first or source type. Also, the field equations of this latter theorem appear to be sufficiently general such that the field equations naturally divide into two distinct classes, a four-solenoidal electromagnetic type class in a relativistic transverse gauge and a four-irrotational class in a relativistic longitudinal gauge.
Momentum due to pressure: A simple model
Authors: Jagannathan Kannan
Published: April 2009

In relativistic fluid dynamics the momentum density of a fluid element consists of two terms—one that depends on the proper density and velocity of the element and another that depends on its proper pressure and velocity. The usual way in which this result is displayed as a second rank tensor does not yield much insight into the origin of the pressure term and is not likely to be of pedagogical value in most undergraduate physics courses. I present a minimal model that offers some insight into the origin of the pressure term in the momentum density.
Nonequilibrium statistical mechanics: A solvable model
Authors: Mazilu I. , Williams H. T.
Published: April 2009

A two-temperature linear spin model is presented as an introduction to nonequilibrium statistical physics. The model involves the concepts that are typical of more realistic nonequilibrium models, but has straightforward steady state solutions and, for small systems, development of the full time dependence for configuration probabilities. The model is accessible to upper-level undergraduates and provides a good check of computer models for larger systems.
Physics of attosecond pulses produced via high harmonic generation
Authors: Varjú Katalin , Johnsson Per , Mauritsson Johan , L’Huillier Anne , López-Martens Rodrigo
Published: April 2009

The physics of extreme ultraviolet attosecond pulse trains generated during the interaction between an intense laser pulse and a gas medium is presented, including a simple model based on the solution of the classical equations of motion of an electron in an oscillating laser field. The reconstruction of attosecond beating by the interference of a two-photon transition is described and used to determine the pulse duration of the emitted attosecond pulses. This application is the basis of a laboratory practical for a graduate atomic physics course.
Exploring the transition from special to general relativity
Authors: Semon Mark D. , Malin Shimon , Wortel Stephanie
Published: April 2009

In a previous paper we discussed two examples of circular motion which are especially useful in relativity courses because they lead to predictions verified by experiments with macroscopic objects. We analyzed these examples by considering motion around an N-gon and then taking the limit as N→∞ and the N-gon becomes a circle. In this paper we use the same approach to illustrate how generalizing special relativity to a theory that includes non-inertial frames can lead to a non-Euclidean geometry. We also derive two properties of clocks at rest in a reference frame traveling on a circular path.
Conceptual development about motion and force in elementary and middle school students
Authors: Dykstra Dewey I. , Sweet Dale R.
Published: April 2009

Methods of physics education research were applied to find what kinds of changes in 4th, 6th, and 8th grade student understanding of motion can occur and at what age. Such findings are necessary for the physics community to effectively discharge its role in advising and assisting pre-college physics education. Prior to and after instruction the students were asked to carefully describe several demonstrated accelerated motions. Most pre-instruction descriptions were of the direction of motion only. After instruction, many more of the students gave descriptions of the motion as continuously changing. Student responses to the diagnostic and to the activity materials revealed the presence of a third “snapshot” view of motion not discussed in the literature. The 4th and 6th grade students gave similar pre-instructional descriptions of the motion, but the 4th grade students did not exhibit the same degree of change in descriptions after instruction. Our findings suggest that students as early as 6th grade can develop changes in ideas about motion needed to construct Newtonian-like ideas about force. Students’ conceptions about motion change little under traditional physics instruction from these grade levels through college level.
Analyzing spike trains with circular statistics
Authors: Takeshita Daisuke , Gale John T. , Montgomery Erwin B. , Bahar Sonya , Moss Frank
Published: April 2009

In neuroscience, specifically electrophysiology, it is common to replace a measured sequence of action potentials or spike trains with delta functions prior to analysis. We apply a method called circular statistics to a time series of delta functions and show that the method is equivalent to the power spectrum. This technique allows us to easily visualize the idea of the power spectrum of spike trains and easily reveals oscillatory and stochastic behavior. We provide several illustrations of the method and an example suitable for students, and suggest that the method might be useful for courses in introductory biophysics and neuroscience.
The fundamental parameter space of controlled thermonuclear fusion
Authors: Lindemuth Irvin R. , Siemon Richard E.
Published: April 2009

We apply a few simple first-principles equations to identify the parameter space in which controlled fusion might be possible. Fundamental physical parameters such as minimum size, energy, and power as well as cost are estimated. We explain why the fusion fuel density in inertial confinement fusion is more than 1011 times larger than the fuel density in magnetic confinement fusion. We introduce magnetized target fusion as one possible way of accessing a density regime that is intermediate between the two extremes of inertial confinement fusion and magnetic confinement fusion and is potentially lower cost than either of these two.
Motion of a hexagonal pencil on an inclined plane
Authors: Rezaeezadeh Amin
Published: April 2009

This article discusses a hexagonal prism rolling down an inclined plane, which is easy to realize experimentally and yields results that are consistent with a simple theory. This investigation would make an excellent undergraduate project.
On the stability of electrostatic orbits
Authors: Banerjee Shubho , Taylor Bradford , Banerjee Anand
Published: April 2009

We analyze the stability of two charged conducting spheres orbiting each other. Due to charge polarization, the electrostatic force between the two spheres deviates significantly from 1∕r2 as they come close to each other. As a consequence, there exists a critical angular momentum, Lc, with a corresponding critical radius rc. For L>Lc two circular orbits are possible: one at r>rc that is stable and the other at r<rc that is unstable. This critical behavior is analyzed as a function of the charge and the size ratios of the two spheres.
Impacts of Dosing Frequency of the Combination Rifampin-Streptomycin on Its Bactericidal and Sterilizing Activities against
Mycobacterium ulcerans
in Mice
Authors: Ji Baohong , Chauffour Aurélie , Aubry Alexandra , Robert Jérome , Ibrahim Murad , Jarlier Vincent
Published: April 2009

Because of operational limitations, a significant proportion of the health centers at the peripheral level are able to provide treatment to Buruli ulcer patients with the combination rifampin (rifampicin)-streptomycin (RIF-STR) only five times weekly (5/7) instead of seven times weekly (7/7), as recommended. The objective of this experiment is to assess the impacts of various dosing frequencies of the combination on its bactericidal and sterilizing activities against
Mycobacterium ulcerans
in mice. The results demonstrate that the bactericidal activities did not differ significantly among five dosing frequencies of the combination, ranging from seven times to twice weekly, whereas the sterilizing activities differed widely. RIF-STR 7/7 was the only regimen that was able to sterilize the infection after 4 to 8 weeks of treatment; the sterilizing activities associated with reduced dosing frequencies were significantly diminished, and 8 weeks of 5/7 administration yielded a relapse rate greater than the generally accepted level of 5%. We recommend that the duration of treatment with 5/7 administration be prolonged beyond 8 weeks and that additional experiments with mice be carried out, with sufficient statistical power to compare the relapse rates of
M. ulcerans
infection between 8 weeks of 7/7 administration and 10 and 12 weeks of 5/7 administration of RIF-STR.
Molecular Characteristics of Travel-Related Extended-Spectrum-β-Lactamase-Producing
Escherichia coli
Isolates from the Calgary Health Region
Authors: Pitout Johann D. D. , Campbell Lorraine , Church Deirdre L. , Gregson Daniel B. , Laupland Kevin B.
Published: April 2009

Extended-spectrum-β-lactamase (ESBL)-producing
Escherichia coli
has recently emerged as a major risk factor for community-acquired, travel-related infections in the Calgary Health Region. Molecular characterization was done on isolates associated with infections in returning travelers using isoelectric focusing, PCR, and sequencing for
bla
CTX-M
s,
bla
TEM
s,
bla
SHV
s,
bla
OXA
s, and plasmid-mediated quinolone resistance determinants. Genetic relatedness was determined with pulsed-field gel electrophoresis using XbaI and multilocus sequence typing (MLST). A total of 105 residents were identified; 6/105 (6%) presented with hospital-acquired infections, 9/105 (9%) with health care-associated community-onset infections, and 90/105 (86%) with community-acquired infections. Seventy-seven of 105 (73%) of the ESBL-producing
E. coli
isolates were positive for
bla
CTX-M
genes; 55 (58%) produced CTX-M-15, 13 (14%) CTX-M-14, six (6%) CTX-M-24, one (1%) CTX-M-2, one (1%) CTX-M-3, and one (1%) CTX-M-27, while 10 (10%) produced TEM-52, three (3%) TEM-26, 11 (11%) SHV-2, and four (4%) produced SHV-12. Thirty-one (30%) of the ESBL-producing
E. coli
isolates were positive for
aac
(
6
′)-
Ib
-
cr
, and one (1%) was positive for
qnrS
. The majority of the ESBL-producing isolates (
n
= 95 [90%]) were recovered from urine samples, and 83 (87%) were resistant to ciprofloxacin. The isolation of CTX-M-15 producers belonging to clone ST131 was associated with travel to the Indian subcontinent (India, Pakistan), Africa, the Middle East, and Europe, while clonally unrelated strains of CTX-M-14 and -24 were associated with travel to Asia. Our study suggested that clone ST131 coproducing CTX-M-15, OXA-1, TEM-1, and AAC(6′)-Ib-cr and clonally unrelated CTX-M-14 producers have emerged as important causes of community-acquired, travel-related infections.
Carriage of CTX-M-15-Producing
Escherichia coli
Isolates among Children Living in a Remote Village in Senegal
Authors: Ruppé Etienne , Woerther Paul-Louis , Diop Abdoulaye , Sene Anne-Marie , Da Costa Annaelle , Arlet Guillaume , Andremont Antoine , Rouveix Bernard
Published: April 2009

Two out of 20 children with no known antibiotic exposure, living in a very remote Senegalese village, were found to be fecal carriers of a multiresistant
Escherichia coli
clone that produced CTX-M-15. This highlights the current massive spread of extended-spectrum β-lactamases, even in isolated communities.
Stable Extended Human Immunodeficiency Virus Type 1 gp41 Coiled Coil as an Effective Target in an Assay for High-Affinity Fusion Inhibitors
Authors: Cai Lifeng , Balogh Edina , Gochin Miriam
Published: April 2009

The human immunodeficiency virus type 1 (HIV-1) gp41 coiled-coil domain is an important target for fusion inhibitors, including the peptide T20, which has been approved as a drug against HIV-1. Research into nonpeptide fusion inhibitors has focused primarily on a hydrophobic pocket located within the coiled coil and has so far yielded compounds with relatively weak fusion inhibitory activity. Here, we describe metal ion-assisted stabilization of an extended 39-residue construct of gp41, which includes residues of the hydrophobic pocket and also of an extended groove N terminal to the hydrophobic pocket. We show that the presence of a metal ion and the high-affinity interaction between the receptor construct and cognate C-peptides result in a simple and highly selective assay for fusion inhibitors that may be used to scan large compound libraries. The long construct presents multiple potential binding sites along the extended coiled-coil groove. We demonstrate the modular use of assay probes to detect whether compounds bind in the hydrophobic pocket or elsewhere along the groove. Rapid detection and quantitation of hits can lead to the discovery of compounds binding to different sites along the groove and provide structure-activity relationship data for optimization. Compounds binding to adjacent sites could be linked to form more potent fusion inhibitors.
Prediction of the Pharmacodynamically Linked Variable of Oseltamivir Carboxylate for Influenza A Virus Using an In Vitro Hollow-Fiber Infection Model System
Authors: McSharry James J. , Weng Qingmei , Brown Ashley , Kulawy Robert , Drusano George L.
Published: April 2009

MDCK cells transfected with the human β-galactoside α-2,6-sialyltransferase 1 gene (AX-4 cells) were used to determine the drug susceptibility and pharmacodynamically linked variable of oseltamivir for influenza virus. For dose-ranging studies, five hollow-fiber units were charged with 10
2
A/Sydney/5/97 (H3N2) influenza virus-infected AX-4 cells and 10
8
uninfected AX-4 cells. Each unit was treated continuously with different oseltamivir carboxylate concentrations in virus growth medium for 6 days. For dose fractionation studies, one hollow-fiber unit received no drug, one unit received a 1× 50% effective concentration (EC
50
) exposure to oseltamivir by continuous infusion, one unit received the same AUC
0-24
(area under the concentration-time curve from 0 to 24 h) by 1-h infusion every 24 h, one unit received the same total exposure in two equal fractions every 12 h, and one unit received the same total exposure in three equal fractions every 8 h. Each infusion dose was followed by a no-drug washout, producing the appropriate half-life for this drug. The effect of the drug on virus replication was determined by sampling the units daily, measuring the amount of released virus by plaque assay, and performing a hemagglutination assay. The drug concentration in the hollow-fiber infection model systems was determined at various times by liquid chromatography-tandem mass spectrometry. The dose-ranging study showed that the EC
50
s for oseltamivir carboxylate for the A/Sydney/5/97 strain of influenza virus was about 1.0 ng/ml. The dose fractionation study showed that all treatment arms suppressed virus replication to the same extent, indicating that the pharmacodynamically linked variable was the AUC
0-24
/EC
50
ratio. This implies that it may be possible to treat influenza virus infection once daily with a dose of 150 mg/day.