bluuebunny/crossref_metadata_2025 huggingface dataset:
An examination of the effects of the criterion functional on optimal fire‐support policies
Authors: Taylor James G. , Brown Gerald G.
Published: May 2007

This paper examines the dependence of the structure of optimal time‐sequential fire‐support policies on the quantification of military objectives by considering four specific problems, each corresponding to a different quantification of objectives (i.e. criterion functional). We consider the optimal time‐sequential allocation of supporting fires during the “approach to contact” of friendly infantry against enemy defensive positions. The combat dynamics are modelled by deterministic Lanchester‐type equations of warfare, and the optimal fire‐support policy for each one‐sided combat optimization problem is developed via optimal control theory. The problems are all nonconvex, and local optima are a particular difficulty in one of them. For the same combat dynamics, the splitting of supporting fires between two enemy forces in any optimal policy (i.e. the optimality of singular subarcs) is shown to depend only on whether the terminal payoff reflects the objective of attaining an “overall” military advantage or a “local” one. Additionally, switching times for changes in the ranking of target priorities are shown to be different (sometimes significantly) when the decision criterion is the difference and the ratio of the military worths (computed according to linear utilities) of total infantry survivors and also the difference and the ratio of the military worths (computed according to linear utilities) of total infantry survivors and also the difference and the ratio of the military worths of the combatants' total infantry losses. Thus, the optimal fire‐support policy for this attack scenario is shown to be significantly influenced by the quantification of military objectives.
An algorithm for a class of loading problems
Authors: Hung Ming S. , Brown J. Randall
Published: May 2007

The loading problem we consinder is to assign a set of discrete objects, each having a weight, to a set of boxes, each of which has a capacity limit, in such a way that every object is assigned to a box and the number of boxes used is minimized.

A characterization of the assignments is offered and used to develop a set of rules for generating nonredundant assignments. The rules are incorporated into an implicit enumeration algorithm. The algorithm is tested against a very good heuristic. Computational experience shows that the algorithm is highly efficient, solving problems of up to 3600 0‐1 variables in a CPU second.
Pseudo‐monotonic interval programming
Authors: Bector C. R. , Bhatt S. K.
Published: May 2007

A pseudo‐monotonic interval program is a problem of maximizing f(x) subject to x ε X = {x ε Rn | a < Ax < b, a, b ε Rm} where f is a pseudomonotonic function on X, the set defined by the linear interval constraints. In this paper, an algorithm to solve the above program is proposed. The algorithm is based on solving a finite number of linear interval programs whose solutions techniques are well known. These optimal solutions then yield an optimal solution of the proposed pseudo‐monotonic interval program.
Differential‐game examination of optimal time‐sequential fire‐support strategies
Authors: Taylor James G.
Published: May 2007

Optimal time‐sequential fire‐support strategies are studied through a two‐person zero‐sum deterministic differential game with closed‐loop (or feedback) strategies. Lanchester‐type equations of warfare are used in this work. In addition to the max‐min principle, the theory of singular extremals is required to solve this prescribed‐duration combat problem. The combat is between two heterogeneous forces, each composed of infantry and a supporting weapon system (artillery). In contrast to previous work reported in the literature, the attrition structure of the problem at hand leads to force‐level‐dependent optimal fire‐support strategies with the attacker's optimal fire‐support strategy requiring him to sometimes split his artillery fire between enemy infantry and artillery (counterbattery fire). A solution phenomnon not previously encountered in Lanchester‐type differential games is that the adjoint variables may be discontinuous across a manifold of discontinuity for both players' strategies. This makes the synthesis of optimal strategies particularly difficult. Numerical examples are given.
Some approximations in multi‐item, multi‐echelon inventory systems for recoverable items
Authors: Muckstadt John A.
Published: May 2007

The optimization problem as formulated in the METRIC model takes the form of minimizing the expected number of total system backorders in a two‐echelon inventory system subject to a budget constraint. The system contains recoverable items – items subject to repair when they fail. To solve this problem, one needs to find the optimal Lagrangian multiplier associated with the given budget constraint.

For any large‐scale inventory system, this task is computationally not trivial. Fox and Landi proposed one method that was a significant improvement over the original METRIC algorithm. In this report we first develop a method for estimating the value of the optimal Lagrangian multiplier used in the Fox‐Landi algorithm, present alternative ways for determining stock levels, and compare these proposed approaches with the Fox‐Landi algorithm, using two hypothetical inventory systems – one having 3 bases and 75 items, the other 5 bases and 125 items. The comparison shows that the computational time can be reduced by nearly 50 percent.

Another factor that contributes to the higher requirement for computational time in obtaining the solution to two‐echelon inventory systems is that it has to allocate stock optimally to the depot as well as to bases for a given total‐system stock level. This essentially requires the evaluation of every possible combination of depot and base stock levels – a time‐consuming process for many practical inventory problems with a sizable system stock level. This report also suggests a simple approximation method for estimating the optimal depot stock level. When this method was applied to the same two hypotetical inventory systems indicated above, it was found that the estimate of optimal depot stock is quite close to the optimal value in all cases. Furthermore, the increase in expected system backorders using the estimated depot stock levels rather than the optimal levels is generally small.
An inventory depletion problem with random and age‐dependent lifetimes
Authors: Thorburn Daniel
Published: May 2007

The following problem is studied. The units of an inventory are used one by one until all have failed. Their lifetimes decrease with their ages, when they are taken out of the inventory. An item of age a is supposed to have a lifetime Y exp(‐a), where Y is a random variable which does not depend on a. It is shown that in order to maximize the total lifetime the items should be taken according to the LIFO principle. This is shown for a certain class of distributions of Y. This class includes the exponential and the Pareto distributions.
All‐integer linear programming — a new approach via dynamic programming
Authors: Cooper Leon , Cooper Mary W.
Published: May 2007

An exact method for solving all‐integer linear‐programming problems is presented. Dynamic‐programming methodology is used to search efficiently candidate hyperplanes for the optimal feasible integer solution. The explosive storage requirements for high‐dimensional dynamic programming are avoided by the development of an analytic representation of the optimal allocation at each stage. Computational results for problems of small to moderate size are also presented.
Maximizing the sum of certain quasiconcave functions using generalized benders decomposition
Authors: Cabot A. Victor
Published: May 2007

In this paper we consider the problem of maximizing the sum of certain quasi‐concave functions over a convex set. The functions considered belong to the classes of functions which are known as nonlinear fractional and binonlinear functions. Each individual function is quasi‐concave but the sum is not. We show that this nonconvex programming problem can be solved using Generalized Benders Decomposition as developed by Geoffrion.
High b‐value q‐space diffusion MRS of nerves: structural information and comparison with histological evidence
Authors: Bar‐Shir Amnon , Cohen Yoram
Published: May 2007

High b‐value q‐space diffusion MRS was used to study the diffusion characteristics of formalin‐fixed swine optic and sciatic nerves over a large range of diffusion times (3.7–99.3 ms). The very short diffusion time range was studied with a 1 ms resolution. The displacement distribution profiles obtained were fitted to a bi‐Gaussian function, and structural parameters were extracted from the q‐space diffusion MRS data. This structural information was correlated with axon sizes obtained by histological examination. It was found that high b‐value q‐space diffusion MRS can easily distinguish between the two nerve types. The root mean square displacements (rmsds) of both the slow and fast diffusing components of the optic nerves were found to be smaller than those of the sciatic nerves. When the rmsd was plotted against the square root of the diffusion time (t), it was found that all four components showed an increase in rmsd; this increase was significantly smaller than expected from the Einstein equation. However, the most restricted component is the slow diffusing component of the optic nerve. This is also the only diffusing component that shows a large change in the slope (i.e. a ‘breaking point’) of the plot of rmsd as a function of t. This rmsd is very similar to the mean axon size of these optic nerves determined histologically. Such a change in slope was less apparent for the slow diffusing component of sciatic nerves, which showed a wider distribution of axon size in histological images. The fast diffusing components of both nerve types showed only a small gradual change in the slope of rmsd plotted against t. These findings are discussed in the context of component assignment, origin of restriction, and relationships between the structural information extracted from q‐space diffusion MRS and histological examination. Copyright © 2007 John Wiley & Sons, Ltd.
Structure–property relationships in glass reinforced polyamide, part 2: The effects of average fiber diameter and diameter distribution
Authors: Thomason J. L.
Published: May 2007

We present the results of an extensive study of the influence of average fiber diameter and the width of the diameter distribution on the performance of injection‐molded glass‐fiber reinforced polyamide 6,6. In the average fiber diameter range from 9 to 18 μm, dry‐as‐molded (DaM) composite unnotched impact and tensile strength decreased significantly. The composite notched impact performance and tensile modulus showed little dependence on fiber diameter. The influence of broadening the fiber diameter distribution by blending glass fiber samples of different average diameter was found to be particularly negative on the level of composite unnotched impact when compared at equal number average diameter. After hydrolysis treatment, the composite tensile strength and modulus exhibited a large drop compared to the DaM results. In contrast, the unnotched impact results became insensitive to fiber diameter after hydrolysis. The average level of unnotched impact after hydrolysis was sufficiently high to show an increase over DaM when the fiber diameter was above 14 μm. Residual fiber length correlated significantly with fiber diameter with a lower average length for thinner fibers. The interfacial shear strength was found to be in the range of 26–34 MPa for DaM composites. There was a highly significant inverse correlation between the DaM interfacial strength and the average fiber diameter. It is shown that results from both tensile and unnotched impact measurements can be brought back to single trend lines by using a Z average value for the average fiber diameter, which is more heavily weighted to the thicker fibers in the distribution. POLYM. COMPOS., 28:331–343, 2007. © 2007 Society of Plastics Engineers
Measurement of low velocity and quasi‐static failure modes in PMMA
Authors: Pearson J.D. , Zikry M.A. , Prabhugoud M. , Peters K.
Published: May 2007

An investigation of the low velocity impact and quasi‐static failure of polymethylmethacrylate (PMMA) based on global and local strain measurements was conducted. Local strains were obtained from surface‐mounted fiber Bragg grating (FBG) sensors, and they were combined with global measurements from quasi‐static indentation and low‐velocity impact experiments to obtain detailed maps of how failure evolves. For both loading regimes, the interactions between the host PMMA specimens and the sensors played a crucial role in the evolution of residual strains. A mapping of the strains clearly shows that strains decrease radially, from high values near the point of impact to far‐field values. Sensors located in critical locations had the highest residual strains prior to PMMA fracture. Furthermore, it was determined that strain transfer to the sensor is strongly influenced by the bonding conditions at the specimen's surface. Because of the debonding of the sensor and the frictional effects associated with the bonding agent, compressive residual strains occurred on the rear‐surface. Hence, a detailed understanding of how strain evolves due to sensor–host interactions and catastrophic fracture can be obtained, which can potentially be used to mitigate damage in PMMA for a range of strain rates. POLYM. COMPOS., 28:381–391, 2007. © 2007 Society of Plastics Engineers
Role of cationic gemini surfactants toward enhanced ninhydrin–tryptophan reaction
Authors: Kabir‐ud‐Din  , Fatma Waseefa
Published: May 2007

In this paper we report the effect of dicationic ‘gemini’ surfactants (CH3)2C16H33N+ (CH2)mN+C16H33(CH3)2, 2Br−(wherem = 4, 5, 6) on the reaction of ninhydrin withDL‐tryptophan. The gemini surfactant micellar media are comparatively more effective than their conventional monomeric counterpart cetyltrimethylammonium bromide (CTAB) micelles. Also, whereas typical rate constant (kψ) increase and leveling‐off regions, just like CTAB, are observed with geminis, the latter produce a third region of increasingkψat higher concentrations. These subsequent increases are ascribed to changes in micellar morphologies, consistent with changes in1H NMR line widths. Quantitative kinetic analysis of the rate constant–[surfactant] data has been performed on the basis of modified pseudophase model. Copyright © 2007 John Wiley & Sons, Ltd.
Reactivities of acridine compounds in hydride transfer reactions
Authors: Lee In‐Sook Han , Kil Hyun Joo , Ji Young Ran
Published: May 2007

Reactivities of acridine derivatives (10‐benzylacridinium ion, 1a+, 10‐methylacridinium ion, 1b+, and 10‐methyl‐9‐phenylacridinium ion, 1c+) have been compared quantitatively for hydride transfer reactions with 1,3‐dimethyl‐2‐substituted phenylbenzimidazoline compounds, 2Ha–h. Reactions were monitored spectrophotometrically in a solvent consisting of four parts of 2‐propanol to one part of water by volume at 25 ± 0.1 °C. Reduction potentials have been estimated for acridine derivatives by assuming that the equilibrium constants for the reductions of 1a+–c+ by 2Hb would be the same in aqueous solution and accepting −361 mV as the reduction potential of the 1‐benzyl‐3‐carbamoylpyridinium ion. The resulting reduction potentials, E, are −47 mV for 1a+, −79 mV for 1b+, and −86 mV for 1c+. Each of acridine derivatives gives a linear Brønsted plot for hydride transfer reactions. The experimental slopes were compared with those obtained by Marcus theory. This comparison shows that the kinetic data are consistent with a one‐step mechanism involving no high‐energy intermediates. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of graft copolymers containing poly(p‐phenylene) main chains and mesogen‐jacketed liquid‐crystalline polystyrene side chains
Authors: Sun Li‐Mei , Fan Xing‐He , Chen Xiao‐Fang , Liu Xiang‐Feng , Zhou Qi‐Feng
Published: May 2007

A series of novel comblike mesogen‐jacketed liquid‐crystalline graft copolymers, poly(p‐phenylene)‐g‐poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (PPP‐g‐PMPCS) copolymers, have been designed and successfully synthesized by a Yamamoto coupling reaction and subsequent atom transfer radical polymerization (ATRP). 1H NMR spectroscopy, ultraviolet–visible spectra, and gel permeation chromatography (GPC) have been used to confirm the molecular structure of the macroinitiator and the copolymers. A study of the polymerization kinetics of ATRP has shown that the molecular weight of the copolymer increases linearly with the conversion of the monomer, whereas the polydispersity remains narrow (≤1.28), indicating that the ATRP of 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene is well controlled. Thermogravimetric analysis and differential scanning calorimetry (DSC) measurements have indicated that the PPP‐g‐PMPCS copolymers have better thermal stabilities than the macroinitiator, and their thermal stabilities increase with increasing molecular weight. The liquid‐crystalline behavior has been examined with polarized optical microscopy, DSC, one‐dimensional wide‐angle X‐ray diffraction (1D WAXD), and two‐dimensional wide‐angle X‐ray diffraction (2D WAXD). The results show that all the comblike copolymers exhibit obvious liquid‐crystalline behaviors, even though the GPC molecular weight of the segments of poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (PMPCS) have been determined to be far less than the critical value of linear PMPCS. Moreover, 1D WAXD measurements show that the temperature at which the comblike mesogen‐jacketed liquid‐crystalline copolymers can transform into a liquid‐crystalline phase is low; about 20 °C in comparison with the linear ones. 2D WAXD analysis has revealed that these comblike copolymers should be assigned to a hexatic columnar nematic (ΦHN) phase. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2543–2555, 2007
End‐functional poly(methyl methacrylate)s via group transfer polymerization
Authors: Gnaneshwar Rudhramyna , Sivaram Swaminathan
Published: May 2007

Hydroxyl‐, amine‐, and lactone‐end‐functional poly(methyl methacrylate)s (PMMA) were prepared with controlled molecular weights and Mw/Mn = 1.06–1.19 via group transfer polymerization. This was achieved by the electrophilic termination of silyl ketene acetal ended PMMAs with benzaldehyde, N‐trimethylsilyl benzaldimine, and 5,6‐dihydro‐2H‐pyran‐2‐one, respectively. The number‐average degree of functionalization, as determined by NMR/SEC, was in the range of 0.70–0.85. A Lewis acid was used for terminating silyl ketene acetal ended PMMA with N‐trimethylsilyl benzaldimine, whereas tetra‐n‐butyl ammonium bibenzoate was used in the case of benzaldehyde and 5,6‐dihydro‐2H‐pyran‐2‐one. MALDI‐TOF MS analysis of the end‐functional polymers indicated the competing formation of cyclic end groups due to a back‐biting reaction along with end‐functional PMMAs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2514–2531, 2007
Quantitative approaches to particle cavitation, shear yielding, and crazing in rubber‐toughened polymers
Authors: Bucknall C. B.
Published: May 2007

Models for rubber particle cavitation, shear yielding, and crazing are reviewed, and their ability to predict the large‐strain deformation behavior of toughened polymers is discussed. An existing model for void initiation and expansion in rubber particles correctly predicts the observed trends: cavitation resistance increases when either the shear modulus or the surface energy of the rubber is increased, or the particle size is reduced. However, further work is needed to improve quantitative modeling of the thermally‐ and stress‐activated void nucleation step. Shear yielding, which is also a rate process, is much better understood; here, the main problems in modeling relate to the formation and evolution of porous shear bands. Craze growth and failure are also reasonably well understood, but previous attempts at modeling have been hampered by uncertainties about craze initiation. To overcome these difficulties, a new theory of crazing is proposed, which treats initiation as a fracture process, and defines a new materials property, Gnasc, the energy required to form unit area of nascent craze. Because nascent crazes are ∼20 nm thick, Gnasc is low: calculations give values <0.5 J m−2 for polystyrene. A new criterion incorporating a plasticity factor fits the data of Sternstein and coworkers on crazing under biaxial loading. In combination with theories of particle cavitation and shear yielding, the fracture mechanics model explains why the balance between crazing and shear yielding is governed by particle size, for example in ABS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1399–1409, 2007
The effect of oxytocin on cell proliferation in the human prostate is modulated by gonadal steroids: implications for benign prostatic hyperplasia and carcinoma of the prostate
Authors: Whittington Kate , Connors Belinda , King Keith , Assinder Steve , Hogarth Karole , Nicholson Helen
Published: May 2007

BACKGROUND

Oxytocin (OT) is implicated in regulating prostate growth. OT concentrations are increased in benign, and decreased in malignant prostate disease. This study investigated whether the altered concentrations of OT present in prostate disease affect the proliferation of malignant and non‐malignant human prostate cells.

METHODS

The effects of varying concentrations of OT and gonadal steroids on cell proliferation of non‐malignant prostatic epithelial (PrEC) and stromal (PrSC) cells and androgen dependent (LNCaP) and independent (PC‐3) malignant cell lines were assessed.

RESULTS

OT (>0.5 nmol · L−1) had no effect on PrEC proliferation when cells were cultured alone. When co‐cultured with PrSC and gonadal steroids, OT inhibited epithelial cell proliferation. OT inhibited PrSC proliferation, when cells were cultured alone. When PrSC were co‐cultured in the presence of estrogen physiological concentrations of OT were inhibitory. No effect on cell proliferation was observed with higher concentrations of OT. OT did not affect the proliferation of malignant cell lines in the absence of androgens but, in the presence of testosterone, low concentrations of OT (<1 nmol · L−1) stimulated proliferation of PC‐3 cells. Disruption of caveolae in the plasma membrane removed the inhibitory effect of OT on PrSC proliferation but did not affect the stimulatory effect of OT on PC‐3 cells cultured in the presence of androgens.

CONCLUSIONS

Changes in prostatic concentrations of OT that occur with aging and malignant disease may act to facilitate cell proliferation. The localization of the OT receptor within the plasma membrane modulates OT's proliferative response in the prostate. Prostate 67: 1132–1142, 2007. © 2007 Wiley‐Liss, Inc.
Molecular properties of two proteins homologous to PduO‐type ATP:cob(I)alamin adenosyltransferase from Sulfolobus tokodaii
Authors: Tanaka Yoshikazu , Sasaki Takashi , Kumagai Izumi , Yasutake Yoshiaki , Yao Min , Tanaka Isao , Tsumoto Kouhei
Published: May 2007

In the thermophilic archaeon Sulfolobus tokodaii, there are two genes homologous to PduO‐type ATP:cob(I)alamin adenosyltransferase, ST1454 and ST2180. To address the structure and function of these two sequence‐related proteins from one organism, we prepared them by using the Escherichia coli expression system and analyzed them by immunoblotting, matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectroscopy, circular dichroism spectrometry, ATP:cobalamin adenosyltransferase assay, and X‐ray crystallography. Immunoblotting and matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectroscopy analyses showed that both these proteins are expressed in S. tokodaii cells as soluble proteins and are spontaneously digested at the N‐terminal region. ATP:cob(I)alamin adenosyltransferase activity was detected for ST1454 but not for ST2180. ST2180 reduced the concentration of cob(I)alamin, suggesting that ST2180 might recognize cob(I)alamin as a ligand. The secondary structure of ST1454 was retained even in 7 M guanidine hydrochroride, whereas that of ST2180 was melted in 4.5 M guanidine hydrochloride. The X‐ray crystal structural analysis revealed that the proteins shared a common structure: a trimer of five‐helix bundles with a clockwise kink. There is a pocket surrounded by highly conserved residues, in which a polypropylene glycol 400 in the crystal structure of ST1454 was captured, suggesting that it is an active site. Structural comparison between these two proteins showed the difference in the number of ion pairs around the proposed active site. On the basis of these results, we propose that ST1454 and ST2180 have related but distinct functions. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Second‐order sliding mode control of underactuated mechanical systems I: Local stabilization with application to an inverted pendulum
Authors: Riachy Samer , Orlov Yuri , Floquet Thierry , Santiesteban Raul , Richard Jean‐Pierre
Published: May 2007

Second‐order sliding mode control synthesis is developed for underactuated mechanical systems, operating under uncertainty conditions. In order to locally stabilize an underactuated system around an unstable equilibrium, an output is specified in such a way that the corresponding zero dynamics is locally asymptotically stable. Then, the desired stability property of the closed‐loop system is provided by applying a quasihomogeneous second‐order sliding mode controller, driving the system to the zero dynamics manifold in finite time. Although the present synthesis exhibits an infinite number of switches on a finite time interval, it does not rely on the generation of first‐order sliding modes, while providing robustness features similar to those possessed by their standard sliding mode counterparts. A second‐order sliding mode appears on the zero dynamics manifold which is of co‐dimension greater than the control space dimension. Performance issues of the proposed synthesis are illustrated in numerical and experimental studies of a cart–pendulum system. Copyright © 2007 John Wiley & Sons, Ltd.
Decentralized MPC of nonlinear systems: An input‐to‐state stability approach
Authors: Raimondo D.M. , Magni L. , Scattolini R.
Published: May 2007

This paper presents stabilizing decentralized model predictive control (MPC) algorithms for discrete‐time nonlinear systems. The overall system under control is composed by a number of subsystems, each one locally controlled with an MPC algorithm guaranteeing the input‐to‐state stability (ISS) property. Then, the main stability result is derived by considering the effect of interconnections as perturbation terms and by showing that also the overall system is ISS. Both open‐loop and closed‐loop min–max formulations of robust MPC are considered. Copyright © 2007 John Wiley & Sons, Ltd.
Simultaneous ℋ︁2/ℋ︁∞ control of uncertain jump systems with functional time‐delays
Authors: Mahmoud Magdi S. , Shi Peng , Boukas El Kebir , Jain Lakhim
Published: May 2007

This paper presents new results pertaining to the control design of a class of linear uncertain systems with Markovian jump parameters. An integral part of the system dynamics is a delayed state in which the time‐delays are mode dependent. The jumping parameters are modelled as a continuous‐time, discrete‐state Markov process and the uncertainties are norm‐bounded. We construct an appropriate Lyapunov–Krasovskii functional and design a simultaneous ℋ︁2/ℋ︁∞ controller which minimizes a quadratic ℋ︁2 performance measure while satisfying a prescribed ℋ︁∞‐norm bound on the closed‐loop system. It is established that sufficient conditions for the existence of the simultaneous ℋ︁2/ℋ︁∞ controller and the associated performance upper bound are cast in the form of linear matrix inequalities. Simulation results are provided and extension to the case where the jumping rates are subject to uncertainties is presented. Copyright © 2007 John Wiley & Sons, Ltd.
Biomimetic Models of the Actin Cytoskeleton
Authors: Mohrdieck Camilla , Dalmas Florent , Arzt Eduard , Tharmann Rainer , Claessens Mireille M. A. E. , Bausch Andreas R. , Roth Alexander , Sackmann Erich , Schmitz Christian H. J. , Curtis Jennifer , Roos Wouter , Schulz Simon , Uhrig Kai , Spatz Joachim P.
Published: May 2007

The cytoskeleton is a complex polymer network that plays an essential role in the functionality of eukaryotic cells. It endows cells with mechanical stability, adaptability, and motility. To identify and understand the mechanisms underlying this large variety of capabilities and to possibly transfer them to engineered networks makes it necessary to have in vitro and in silico model systems of the cytoskeleton. These models must be realistic representatives of the cellular network and at the same time be controllable and reproducible. Here, an approach to design complementary experimental and numerical model systems of the actin cytoskeleton is presented and some of their properties discussed.
Install or invoke?: The optimal trade‐off between performance and cost in the design of multi‐standard reconfigurable radios
Authors: Rodriguez Virgilio , Moy Christophe , Palicot Jacques
Published: May 2007

We approach the design of multi‐standard reconfigurable radio as a choice between two extremes: (a) installing complex, self‐contained dedicated components that provide high performance at a high cost (‘Velcro approach’), versus (b) supporting all targeted standards through primitive lower level components, which reduces cost but maximises latency. To find the optimal trade‐off between performance and cost, we build a mathematical model, in which we represent the design choices through a graph of progressively simpler functional modules. We illustrate our approach through a simple but realistic design example. Additionally, we show that this optimisation can be reformulated as a version of the well‐known network‐design problem, which opens the door to a wealth of results, algorithms and experience, already available in the scientific literature. We identify some specific algorithms that can help us find the optimal design and discuss limitations and future directions of our research program. Copyright © 2007 John Wiley & Sons, Ltd.
On channel adaptive energy management with available bandwidth estimation in wireless sensor networks
Authors: Lin Xiao‐Hui , Kwok Yu‐Kwong , Wang Hui
Published: May 2007

To enhance the lifetime of a sensor network which consists of hundreds or even thousands of resource‐limited devices, energy efficient communication is mandatory. Despite that a plethora of work has been done in designing energy efficient protocols for sensor networks, the time‐varying nature of wireless channel is largely unexplored. Indeed, we believe that a cross‐layer design on power aware communication is necessary to further optimize energy usage. In this paper, we propose a new channel adaptive power aware protocol, called CAEM, which works by dynamically adjusting the data throughput under different channel conditions with the help of an adaptive channel coding and modulation facility. Each sensor device judiciously accesses the wireless medium in that communication activity is reduced for devices under poor channel conditions. Simulation results indicate that the proposed CAEM protocol can lead to energy conservation by as much as 30 per cent. Furthermore, CAEM is also efficient in channel utilization as it generates a higher data throughput even under heavy traffic load. Copyright © 2007 John Wiley & Sons, Ltd.
When are ant‐attractant devices a worthwhile investment?Vicia fabaextrafloral nectaries andLasius nigerants
Authors: Oliver Thomas H. , Cook James M. , Leather Simon R.
Published: May 2007

Most studies aiming to determine the beneficial effect of ants on plants simply consider the effects of the presence or exclusion of ants on plant yield. This approach is often inadequate, however, as ants interact with both non‐tended herbivores and tended Homoptera. Moreover, the interaction with these groups of organisms is dependent on ant density, and these functional relationships are likely to be non‐linear. A model is presented here that segregates plant herbivores into two categories depending on the sign of their numerical response to ants (myrmecophiles increase with ants, non‐tended herbivores decline). The changes in these two components of herbivores with increasing ant density and the resulting implications for ant‐plant mutualisms are considered. It emerges that a wide range of ant densities needs to be considered as the interaction sign (mutualism or parasitism) and strength is likely to change with ant density. The model is used to interpret the results of an experimental study that varied levels ofAphis fabaeinfestation andLasius nigerant attendance onVicia fababean plants. Increasing ant density consistently reduced plant fitness and thus, in this location, the interaction between the ants and the plant can be considered parasitic. In theVicia fabasystem, these costs of ants are unlikely to be offset by other beneficial agents (e.g., parasitoids), which also visit extrafloral nectaries.
Omitted Variables in Multilevel Models
Authors: Kim Jee-Seon , Frees Edward W.
Published: May 2007

Statistical methodology for handling omitted variables is presented in a multilevel modeling framework. In many nonexperimental studies, the analyst may not have access to all requisite variables, and this omission may lead to biased estimates of model parameters. By exploiting the hierarchical nature of multilevel data, a battery of statistical tools are developed to test various forms of model misspecification as well as to obtain estimators that are robust to the presence of omitted variables. The methodology allows for tests of omitted effects at single and multiple levels. The paper also introduces intermediate-level tests; these are tests for omitted effects at a single level, regardless of the presence of omitted effects at a higher level. A simulation study shows, not surprisingly, that the omission of variables yields bias in both regression coefficients and variance components; it also suggests that omitted effects at lower levels may cause more severe bias than at higher levels. Important factors resulting in bias were found to be the level of an omitted variable, its effect size, and sample size. A real data study illustrates that an omitted variable at one level may yield biased estimators at any level and, in this study, one cannot obtain reliable estimates for school-level variables when omitted child effects exist. However, robust estimators may provide unbiased estimates for effects of interest even when the efficient estimators fail, and the one-degree-of-freedom test helps one to understand where the problem is located. It is argued that multilevel data typically contain rich information to deal with omitted variables, offering yet another appealing reason for the use of multilevel models in the social sciences.
Comparing Subcutaneous Adipose Tissue in Beef and Muskox with Emphasis on trans 18:1 and Conjugated Linoleic Acids
Authors: Dugan Michael E. R. , Kramer John K. G. , Robertson Wayne M. , Meadus William J. , Aldai Noelia , Rolland David C.
Published: May 2007

Muskox (Ovibos moschatus) are ruminant animals native to the far north and little is known about their fatty acid composition. Subcutaneous adipose tissue (backfat) from 16 wild muskox was analyzed and compared to backfat from 16 barley fed beef cattle. Muskox backfat composition differed substantially from beef and the most striking difference was a high content of 18:0 (26.8 vs. 9.77%). This was accompanied by higher levels of most other saturated fatty acids except beef had more 16:0. Muskox backfat also had a lower level of cis‐18:1 and this was related to a lower expression of steroyl‐CoA desaturase mRNA. Beef backfat had a higher level of total trans‐18:1 (4.25 vs. 2.67%). The most prominent trans‐18:1 isomers in beef backfat were 10t‐18:1 (2.13%) and 11t‐18:1 (0.77%) whereas the most prominent isomers in muskox backfat were 11t‐18:1 (1.41%), 13t/14t‐ (0.27%) and 16t‐18:1 (0.23%). The total conjugated linoleic acid (CLA) content was higher in beef backfat than muskox (0.67 vs. 0.50%) with 9c,11t‐18:2 as the most abundant CLA isomer. The second most abundant CLA isomer in beef backfat was 7t,9c‐18:2 (0.10%) whereas in muskox it was 11t13c‐18:2 (0.04%). Muskox backfat had a higher content of 18:3n‐3 and its elongation and desaturation products 20:5n‐3, 22:5n‐3 and 22:6n‐3 and a lower n‐6/n‐3 ratio. Overall, the high forage diet of muskox seemed to produce a healthier fatty acid profile and highlighted the need to develop feeding strategies for intensively raising beef that will not negatively impacting fatty acid composition.
Identifying estrogen receptor target genes
Authors: Welboren Willem-Jan , Stunnenberg Henk G. , Sweep Fred C.G.J. , Span Paul N.
Published: May 2007

The estrogen receptor (ER) is a ligand inducible transcription factor that regulates a large number of target genes. These targets are particularly relevant in breast cancer, where the sensitivity of the tumor to estrogens determines whether the patients can be treated with endocrine therapy such as tamoxifen. Identifying genomic ER targets is a daunting task. Quantifying expression levels of suspected target genes after estradiol stimulation or, more recently, using expression microarrays to this effect will reveal which genes are regulated by estradiol, however, without discriminating between direct and indirect targets. The identification of the palindromic sequence that defines the estrogen responsive element (ERE) allows for the in silico discovery of putative ER targets in the genome. However the ER can also bind imperfect EREs and half sites, and can bind indirectly via other factors. Chromatin immunoprecipitation (ChIP) can yield all ER genomic target sites. Coupling of ChIP with genome‐wide tiling arrays allows for the genome‐wide unbiased identification of direct ER target sequences.
WITCHCRAFT, POLITICS, AND MEMORY IN SEVENTEENTH-CENTURY ENGLAND
Authors: GASKILL MALCOLM
Published: May 2007

This article weaves together two episodes separated by a generation. The inciting event is the trial in 1653 of Anne Bodenham, an elderly cunning woman in Salisbury, who found herself embroiled in a feud in a gentry household, set against the turbulent backdrop of a divided city. Her arrest and examination evoked painful memories of an earlier scandal, the fateful association of the duke of Buckingham with Dr John Lambe, a sorcerer whom Bodenham claimed to have served in the 1620s. These tales, in turn, echoed an even older awareness of the perils of the diabolic, most prominently the pact of Dr Faustus. Together these narrative strands demonstrate how feelings of public disgust at Stuart corruption were revived in the commonwealth era and used as a polemical device by puritan activists. Both stories are rich in gossip, rumour, rhymes, libels, anonymous notes, and the practical uses of printed works, not to mention spells and curses, visions and dreams. As such, this article also shows just how complex a witch-trial could be, and serves as a reminder of the sophistication, ingenuity, and ebullience of seventeenth-century communications and consciousness across the social order.
Huguenot Immigrants and the Formation of National IDENTITIES, 1548–1787
Authors: LACHENICHT SUSANNE
Published: May 2007

This article addresses the extent to which Protestant states in Europe and North America depicted the French Protestants who had found refuge in these states, as having contributed to the process of nation building and the formation of national identity. It is shown that the arrival of Huguenots was portrayed positively as the historians of these nations could contend that Huguenots had been absorbed readily into the host society because their virtues of frugality and industry corresponded admirably with the ethic of their hosts. The article demonstrates that, in no case, did this depiction correspond with reality. It shows that within those countries of refuge, Huguenots fostered a distinctive French Protestant identity that enabled them to remain aloof from the culture of their host society. In all cases Huguenots asserted themselves as a self-confident minority, convinced of the superiority of their language and culture who believed themselves to be privileged in this world as in the next. When national histories came to be composed, this dimension to the Huguenot minorities came to be expunged from historical memory as was also the fact that the Huguenots were but one of several minorities whose distinctiveness had contributed largely to the shaping of the state, culture, and society of the emerging nation-states.
NAPOLEON AND THE ‘CITY OF SMUGGLERS’, 1810–1814
Authors: DALY GAVIN
Published: May 2007

In the final years of the Napoleonic Wars, Napoleon allowed English smugglers entry into the French ports of Dunkirk and Gravelines, encouraging them to run contraband back and forth across the Channel. Gravelines catered for up to 300 English smugglers, housed in a specially constructed compound known as the ‘city of smugglers’. Napoleon used the smugglers in the war against Britain. The smugglers arrived on the French coast with escaped French prisoners of war, gold guineas, and English newspapers; and returned to England laden with French textiles, brandy, and gin. Smuggling remains a neglected historical subject, and this episode in particular – the relationship between English smugglers and the Napoleonic state between 1810 and 1814 – has attracted little scholarly interest. Yet it provides a rich historical source, illuminating not only the history of Anglo-French Channel smuggling during the early nineteenth century, but offering insights into the economic, social, and maritime history of the Napoleonic Wars.
THE ‘OLD’ BRITISH HISTORIES?
Authors: OHLMEYER JANE H.
Published: May 2007

Protestant war: the ‘British’ of Ireland and the wars of the three kingdoms. By Robert Armstrong. Manchester: Manchester University Press, 2005. Pp. viii+261. ISBN 0-7190-6983-1. £55.00.

The origins of sectarianism in early modern Ireland. Edited by Alan Ford and John McCafferty. Cambridge: Cambridge University Press, 2005. Pp. ix+249. ISBN 0-521-83755-3. £50.00.

Scottish communities abroad in the early modern period. Edited by Alexia Grosjean and Steve Murdoch. Leiden: Brill Academic Press, 2005. Pp. xxi+417. ISBN 90-04-14306-8. €147.00.

Lord Broghill and the Cromwellian union with Ireland and Scotland. By Patrick Little. Woodbridge: Boydell Press, 2004. Pp. xvi+270. ISBN 184383099X. £50.00.

The British revolution, 1629–1660. By Allan Macinnes. Houndsmills: Palgrave Macmillan, 2005. Pp. xi+337. ISBN 0-333-59749-4. £59.50.

1659: the crisis of the Commonwealth. By Ruth E. Mayers. Woodbridge: Boydell Press, 2004. Pp. xii+306. ISBN 0861932684. £45.00.

The English Atlantic in an age of revolution, 1640–1661. By Carla Gardina Pestana. Cambridge, MA: Harvard University Press, 2004. Pp. xiii+342. ISBN 0-674-01502-9. £32.95.

Politics and war in the three Stuart kingdoms, 1637–1649. By David Scott. Houndsmills: Palgrave Macmillan, 2004. Pp. xiv+233. ISBN 0-333-65873-6. £52.50.

The Irish and British wars, 1637–1654: triumph, tragedy, and failure. By Scott Wheeler. London: Routledge, London, 2002. Pp. x+272. ISBN 0415221315. £32.50.

Britain in revolution, 1625–1660. By Austin Woolrych. Oxford: Oxford University Press, 2002. Pp. xi+814. ISBN 0-19-820081-1. £25.00.
Introduction
Authors: Walker Clive
Published: May 2007

This issue of Microscopy and Microanalysis contains papers
from the Seventh Regional Workshop of the European Microbeam Analysis
Society (EMAS) on Electron Probe Microanalysis of Materials
Today—Practical Aspects that took place May 13–16, 2006 in
Karlsruhe, Germany. The meeting was organized in collaboration with the
Institute for Transuranium Elements (ITU) of the Joint Research Centre of
the European Commission.
The Use of SIMS and SEM for the Characterization of Individual Particles with a Matrix Originating from a Nuclear Weapon
Authors: Ranebo Ylva , Eriksson Mats , Tamborini Gabriele , Niagolova Nedialka , Bildstein Olivier , Betti Maria
Published: May 2007

The application of scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) for characterization of mixed plutonium and uranium particles from nuclear weapons material is presented. The particles originated from the so-called Thule accident in Greenland in 1968. Morphological properties have been studied by SEM and two groups were identified: a “popcorn” structure and a spongy structure. The same technique, coupled with an energy-dispersive X-ray (EDX) spectrometer, showed a heterogeneous composition of Pu and U in the surface layers of the particles. The SIMS depth profiles revealed a varying isotopic composition indicating a heterogeneous mixture of Pu and U in the original nuclear weapons material itself. The depth distributions agree with synchrotron-radiation-based μ-XRF (X-ray fluorescence microprobe) measurements on the particle (Eriksson, M., Wegryzynek, D., Simon, R., & Chinea-Cano, E., in prep.) when a SIMS relative sensitivity factor for Pu to U of 6 is assumed. Different SIMS identified isotopic ratio groups are presented, and the influence of interferences in the Pu and U mass range are estimated. The study found that the materials are a mixture of highly enriched235U (235U:238U ratio from 0.96 to 1.4) and so-called weapons grade Pu (240Pu:239Pu ratio from 0.028 to 0.059) and confirms earlier work reported in the literature.
Construction and Establishment of a New Environmental Chamber to Study Real-Time Cardiac Development
Authors: Orhan Gülay , Baron Stephan , Norozi Kambiz , Männer Jörg , Hornung Oliver , Blume Holger , Misske Judith , Heimann Bodo , Wessel Armin , Yelbuz T. Mesud
Published: May 2007

Heart development, especially the critical phase of cardiac looping, is a complex and intricate process that has not yet been visualized “live” over long periods of time. We have constructed and established a new environmental incubator chamber that provides stable conditions for embryonic development with regard to temperature, humidity, and oxygen levels. We have integrated a video microscope in the chamber to visualize the developing heart in real time and present the first “live” recordings of a chick embryo in shell-less culture acquired over a period of 2 days. The time-lapse images we show depict a significant time window that covers the most critical and typical morphogenetic events during normal cardiac looping. Our system is of interest to researchers in the field of embryogenesis, as it can be adapted to a variety of animal models for organogenesis studies including heart and limb development.