bluuebunny/crossref_metadata_2025 huggingface dataset:
The Wiener process between a reflecting and an absorbing barrier
Authors: Schwarz Wolfgang
Published: April 2006

We consider a Wiener process between a reflecting and an absorbing barrier and derive a series solution for the transition density of the process and for the density of the time to absorption. If the drift is towards the reflecting barrier, the variance is not too large, and the distance of the barriers is not too small, the leading term of the series derives from imaginary solutions of the basic eigenvalue equation of this problem. It is shown that these leading terms often make the dominant contribution to the complete series. Finally, we consider previous attempts by Fürth [3], Cox and Miller [1], and by Goel and Richter-Dyn [5] to solve the stated problem and point out, in some detail, why their solutions are wrong.
On the local limit theorem for non-uniformly ergodic Markov chains
Authors: Séva Marc
Published: April 2006

Using an approach similar to that of Guivarc'h and Hardy (1988), we show that the local limit theorem holds for a Markov chain on a countable state space, with non-uniform ergodicity, when the recurrence is fast enough. We present a detailed study of a typical example, the reflected random walk on the positive half-line with negative mean and finite exponential moment. The results can be extended to some random walks on ℕ.
Phase transitions of some non-linear stochastic models
Authors: Feng Shui
Published: April 2006

A class of non-linear stochastic models is introduced. Phase transitions, critical points and the domain of attraction are discussed in detail for some concrete examples. For one of the examples the explicit expression for the domain of attraction and the rates of convergence are obtained.
On effects of discretization on estimators of drift parameters for diffusion processes
Authors: Kloeden P. E. , Platen E. , Schurz H. , Sørensen M.
Published: April 2006

In this paper statistical properties of estimators of drift parameters for diffusion processes are studied by modern numerical methods for stochastic differential equations. This is a particularly useful method for discrete time samples, where estimators can be constructed by making discrete time approximations to the stochastic integrals appearing in the maximum likelihood estimators for continuously observed diffusions. A review is given of the necessary theory for parameter estimation for diffusion processes and for simulation of diffusion processes. Three examples are studied.
Optimal foraging of a reproducing animal as a discounted reward problem
Authors: Merad S. , McNamara J. M.
Published: April 2006

A model in which a foraging animal can reproduce if its energy reserves reach a critical level is presented. The animal's reserves are modelled as a finite-state Markov chain. The animal has the choice between foraging options which may have the same mean net gain but differ in their variances. In addition to starvation, animals are subject to death because of predation, bad weather, and so on. We focus on the case where the rate of mortality due to these sources is the same under all options. We investigate policies that maximise the expected lifetime reproductive success. It is found that the optimal value function is concave at low reserves (low-variance action region) and convex at high reserves (high-variance action region). The value function under the low-variance action has also the same shape and the same inflexion point. This result allows us to compute optimal policies just by looking at the low-variance value function. The result is also used to show that increasing the mortality rate increases the high-variance region under the optimal policy. The pattern of risk-sensitive behaviour predicted by this model is in contrast to that predicted by a similar model in which no reproduction occurs and the optimality criterion is to minimise the probability of death (McNamara (1990)).
A note on a model for restoring a destroyed region
Authors: Hüsler J.
Published: April 2006

We introduce a model for the healing process of a destroyed region and use some relations to the coverage models. The restoring model depends on the region which is hit n times at random. Each random part of the region which is destroyed is restored at a certain fixed speed, but the restoring process may start after a random delay. We focus mainly on the total healing time until the whole region is restored, and analyse its limit distribution as n tends to ∞. The dependence of this limit distribution on the different ingredients is of interest. We consider two cases with different geometrical influence. One case is restricted to a one-dimensional region, that means the circumference of a circle or the unit interval as region. The results follow from extreme value theory. We discuss also some particular cases and examples.
Generalized adaptive exponential smoothing procedures
Authors: Herkenrath Ulrich
Published: April 2006

The classical exponential smoothing procedure to be applied to a sequence of observations is modified into some adaptive variants and also generalized to the recursive scheme

This means that given the history of observations and smoothed values up to time n, the updated smoothed value Wn +1 is given by a function u of Wn and Xn, which satisfies only certain structural properties. We study these procedures within the framework of random systems with complete connections and exploit results from Markov process theory to study the sequence . A broad class of ‘smoothing functions' u, which induce sequences with nice statistical properties, is presented. A method to estimate the limit of the expected smoothed values is also developed.,
Variants of the Choquet–Deny theorem with applications
Authors: Fosam E. B. , Shanbhag D. N.
Published: April 2006

A characterization of the exponential distribution based on a relevation-type equation and its discrete version are extended to the case of multidimensional spaces via variants of the Choquet–Deny theorem. Comments on some recent results in the literature are made.
Simplified bounds on the tails of compound distributions
Authors: Willmot G. E. , Lin Xiaodong
Published: April 2006

Upper and lower bounds are derived for the tail probabilities of compound distributions using simple properties of the claim size distribution. General bounds are then obtained for various classes of claim size distributions. Some examples are given.
Stationary M/G/1 excursions in the presence of heavy tails
Authors: Asmussen Søren , Klüppelberg Claudia
Published: April 2006

It is shown that the stationary excursions above level x for the stationary M/G/1 queue with the service time distribution belonging to a certain class of subexponential distributions are asymptotically of two types as x →∞: either the excursion starts with a jump from a level which is O(1) and the initial excess over x converges to ∞, or it starts from a level of the form x – O(1) and the excess has a proper limit distribution. The two types occur with probabilities ρ, resp. 1 – ρ.
Replacement of train wheels: an application of dynamic reversal of a Markov process
Authors: Gates David , Westcott Mark
Published: April 2006

A problem of regrinding and recycling worn train wheels leads to a Markov population process with distinctive properties, including a product-form equilibrium distribution. A convenient framework for analyzing this process is via the notion of dynamic reversal, a natural extension of ordinary (time) reversal. The dynamically reversed process is of the same type as the original process, which allows a simple derivation of some important properties. The process seems not to belong to any class of Markov processes for which stationary distributions are known.
An interesting random walk on the non-negative integers
Authors: Neuts Marcel F.
Published: April 2006

A particular random walk on the integers leads to a new, tractable Markov chain. Of the stationary probabilities, we discuss the existence, some analytic properties and a factorization which leads to an algorithmic procedure for their numerical computation. We also consider the positive recurrence of some variants which each call for different mathematical arguments. Analogous results are derived for a continuous version on the positive reals.
Weak convergence of conditioned birth and death processes
Authors: Roberts G. O. , Jacka S. D.
Published: April 2006

We consider the problem of conditioning a non-explosive birth and death process to remain positive until time T, and consider weak convergence of this conditional process as T → ∞. By a suitable almost sure construction we prove weak convergence. The almost sure construction used is of independent interest but relies heavily on the strong monotonic properties of birth and death processes.
Distribution of the final extent of a rumour process
Authors: Lefevre Claude , Picard Philippe
Published: April 2006

A rumour model due to Maki and Thompson (1973) is slightly modified to incorporate a continuous-time random contact process and varying individual behaviours in front of the rumour. Two important measures of the final extent of the rumour are provided by the ultimate number of people who have heard the rumour, and the total personal time units during which the rumour is spread. Our purpose in this note is to derive the exact joint distribution of these two statistics. That will be done by constructing a family of martingales for the rumour process and then using a particular family of Gontcharoff polynomials.
On the identification of continuous-time Markov chains with a given invariant measure
Authors: Pollett P. K.
Published: April 2006

In [14] a necessary and sufficient condition was obtained for there to exist uniquely a Q-process with a specified invariant measure, under the assumption that Q is a stable, conservative, single-exit matrix. The purpose of this note is to demonstrate that, for an arbitrary stable and conservative q-matrix, the same condition suffices for the existence of a suitable Q-process, but that this process might not be unique. A range of examples is considered, including pure-birth processes, a birth process with catastrophes, birth-death processes and the Markov branching process with immigration.
Maximization of a survival probability and its application
Authors: Mi Jie
Published: April 2006

When a mission is assigned, it often is the case that the component used to perform the task is required to work properly during the period of the mission time. In other words, the probability of the event that this component does not fail within the allowable mission time should be as large as possible. This problem is considered for the case when the lifetime of a component has a bathtub-shaped failure rate function, and it is found that burn-in procedure is beneficial. An application of this result to the problem of minimizing the mean number of failures in a given period of mission time is also considered.
A note on the existence of regeneration times
Authors: Sigman Karl , Thorisson Hermann , Wolff Ronald W.
Published: April 2006

We rigorously prove that for a stochastic process, , the existence of a first regeneration time, R1, implies the existence of an infinite sequence of such times, {R1, R2, · ·· }, and hence that the definition of regenerative process need only demand the existence of a first regeneration time. Here we include very general processes up to and including processes where cycles are stationary but not necessarily independent and identically distributed.
Dynamic bandwidth allocation for ATM switches
Authors: Hsu Ivy , Walrand Jean
Published: April 2006

We explore a dynamic approach to the problems of call admission and resource allocation for communication networks with connections that are differentiated by their quality of service requirements. In a dynamic approach, the amount of spare resources is estimated on-line based on feedbacks from the network's quality of service monitoring mechanism. The schemes we propose remove the dependence on accurate traffic models and thus simplify the tasks of supplying traffic statistics required of network users. In this paper we present two dynamic algorithms. The objective of these algorithms is to find the minimum bandwidth necessary to satisfy a cell loss probability constraint at an asynchronous transfer mode (ATM) switch. We show that in both schemes the bandwidth chosen by the algorithm approaches the optimal value almost surely. Furthermore, in the second scheme, which determines the point closest to the optimal bandwidth from a finite number of choices, the expected learning time is finite.
Networks of queues with batch services and customer coalescence
Authors: Chao Xiuli , Pinedo Michael , Shaw Dequan
Published: April 2006

Consider a queueing network with batch services at each node. The service time of a batch is exponential and the batch size at each node is arbitrarily distributed. At a service completion the entire batch coalesces into a single unit, and it either leaves the system or goes to another node according to given routing probabilities. When the batch sizes are identical to one, the network reduces to a classical Jackson network. Our main result is that this network possesses a product form solution with a special type of traffic equations which depend on the batch size distribution at each node. The product form solution satisfies a particular type of partial balance equation. The result is further generalized to the non-ergodic case. For this case the bottleneck nodes and the maximal subnetwork that achieves steady state are determined. The existence of a unique solution is shown and stability conditions are established. Our results can be used, for example, in the analysis of production systems with assembly and subassembly processes.
A proof of the persistence criterion for a class of superprocesses
Authors: Wang Yong-Jin
Published: April 2006

Gorostiza and Wakolbinger (1991), and Dawson and Perkins (1991) established the same persistence criterion for a class of critical branching particle systems and for a class of superprocesses respectively. In this note we take another approach to the criterion and present a simpler proof of it.
Synthesis of Methylenebis(phosphonate) Analogs of Dinucleotide Pyrophosphates
Authors: Pankiewicz Krzysztof W. , Gao Guangyao , Patterson Steven E.
Published: April 2006

A facile method is described for preparation of nonsymmetrical P1,P2‐methylenebis(phosphonate) diesters based on the 31P‐NMR‐controlled reaction of methylenebis(phosphonate) monoesters with diisopropylcarbodiimide, resulting in the formation of the intermediate P1,P4‐disubstituted bicyclic trisanhydride. This intermediate, after treatment with an another nucleoside, carbohydrate, or alcohol followed by hydrolysis, is converted into the corresponding methylenebis(phosphonate) diester. An analog of a natural dinucleotide pyrophosphate can be obtained when a nucleoside 5′‐methylenebis(phosphonate) is coupled with another nucleoside. This method is suitable for preparation of metabolically stable (resistant to phosphodiesterase cleavage) analogs of NAD, FAD, and related natural pyrophosphates. The resulting compounds are useful for mechanistic studies of enzymes that use the natural pyrophosphates as cofactors or substrates, and in development of inhibitors that have potential applications as therapeutic agents.
Cover Picture: Fast and Reversible Surface Redox Reaction in Nanocrystalline Vanadium Nitride Supercapacitors (Adv. Mater. 9/2006)
Authors: Choi D. , Blomgren G. E. , Kumta P. N.
Published: April 2006

The cover shows a high magnification transmission electron microscopy image of VN nanoparticles that exhibit enhanced supercapacitor response. The high capacitance is due to V undergoing a series of highly reversible redox reactions. These involve a transition between II–IV oxidation states via hydroxyl bonding confined to a few atomic layers of vanadium oxides formed on the surface of the underlying nitride, as discussed by Kumta and co‐workers on p. 1178.
Electronegative low‐density lipoprotein subfraction from type 2 diabetic subjects is proatherogenic and unrelated to glycemic control
Authors: Benítez Sónia , Pérez Antonio , Sánchez‐Quesada José Luis , Wagner Ana María , Rigla Mercedes , Arcelus Rosa , Jorba Óscar , Ordóñez‐Llanos Jordi
Published: April 2006

Background

The physicochemical and biological characteristics of electronegative low‐density lipoprotein (LDL) (LDL(−)) from type 2 diabetic patients (DM2), before and after insulin therapy, were studied.

Methods

Total LDL was subfractionated in LDL(+) (native LDL) and LDL(−) by anion‐exchange chromatography.

Results

The proportion of LDL(−) was increased in plasma from DM2 patients compared to control subjects (13.8 ± 4.6% versus 6.1 ± 2.5, P < 0.05) and was not modified after glycemic optimization (14.0 ± 5.9%). LDL(−) from DM2 patients presented similar differential characteristics versus LDL(+) than LDL(−) from controls; that is, decreased apoB and oxidizability, and increased triglyceride, nonesterified fatty acids (NEFA), apoE, apoC‐III, platelet‐activating factor (PAF) acetylhydrolase activity and aggregability. No difference in particle size, antioxidants, malondialdehyde (MDA), fructosamine or glycated low‐density lipoprotein (gLDL) was observed between LDL subfractions. Concerning differences between LDL subfractions isolated from DM2 and from control subjects, the former showed increased MDA, fructosamine and gLDL proportion and decreased LDL size and antioxidant content. The only effect of glycemic optimization was a decrease in fructosamine and gLDL in LDL(+) from DM2 subjects. LDL(−) from DM2 patients presented low binding affinity to the low‐density lipoprotein receptor (LDLr) in cultured fibroblasts compared to LDL(+) and two‐ to threefold increased ability to release interleukin‐8 (IL‐8) and monocyte chemotactic protein 1 (MCP‐1) in endothelial cells.

Conclusion

These results suggest that, although nonenzymatic glycosylation and oxidation are increased in type 2 diabetes, these features would not be directly involved in the generation of LDL(−). Moreover, LDL(−) properties suggest that the high proportion observed in plasma could promote accelerated atherosclerosis in DM2 patients through increased residence time in plasma and induction of inflammatory responses in artery wall cells. Copyright © 2006 John Wiley & Sons, Ltd.
Quantifying hydrological budgets and pathways in a small upland catchment using a combined modelling and tracer approach
Authors: Dunn S. M. , Vinogradoff S. I. , Thornton G. J. P. , Bacon J. R. , Graham M. C. , Farmer J. G.
Published: April 2006

Hydrological budgets and flow pathways have been quantified for a small upland catchment (1.76 km2) in the northeast of Scotland. Water balance calculations for four subcatchments identified spatial variability within the catchment, with an estimated runoff enhancement of up to 25% for the upper western area, compared with the rest of the catchment. Data from spatial hydrochemical sampling, over a range of flow conditions, were used to identify the principal hillslope runoff mechanisms within the catchment. A hydrochemical mixing analysis revealed that runoff emerging from springs in various locations of the hillslope accounted for a significant proportion of flow in the streams, even during storm events. A hydrological model of the catchment was calibrated using the calculated stream flows for four locations, together with results from the mixing analysis for different time points. The calibrated model was used to predict the temporal variability in contributions to stream flow from the hillslope springs and soil water flows. The overall split ranged from 57%:43% spring water:soil water in the upper eastern subcatchment, to 76%:24% in the upper western subcatchment. Copyright © 2006 John Wiley & Sons, Ltd.
Porous silk fibroin 3‐D scaffolds for delivery of bone morphogenetic protein‐2 in vitro and in vivo
Authors: Karageorgiou Vassilis , Tomkins Michael , Fajardo Robert , Meinel Lorenz , Snyder Brian , Wade Katherine , Chen Jake , Vunjak‐Novakovic Gordana , Kaplan David L.
Published: April 2006

Bone morphogenetic protein‐2 (BMP‐2) plays a key role in osteogenesis. Biomaterials used for the sustained delivery of BMP‐2 in vivo have shown therapeutic benefits. In the present study, BMP‐2 was loaded in porous silk fibroin scaffolds derived from silkworm cocoons (2.4 ± 0.14 μg per scaffold). The release profile of BMP‐2 under dynamic culture conditions (spinner flasks) showed that after 1 week in culture 25% of the initial BMP‐2 was retained adsorbed to the scaffold; up to 4 weeks no additional BMP‐2 was released. BMP‐2 induced human bone marrow stromal cells (hMSCs) to undergo osteogenic differentiation when the seeded scaffolds were cultured in medium supplemented with osteogenic stimulants for 4 weeks, based on elevated alkaline phosphatase activity, calcium deposition, and transcript levels for bone sialoprotein, osteopontin, osteocalcin, BMP‐2, and cbfa‐1. Micro‐computed tomography revealed densely deposited mineral at the center of the scaffolds. In contrast, hMSCs cultured in control scaffolds (no BMP‐2) exhibited limited osteogenesis. When implanted in critical sized cranial defects in mice, scaffolds loaded with BMP‐2 and seeded with hMSCs resulted in significant bone ingrowth. These results were qualitatively similar to scaffolds loaded with BMP‐2 but no hMSCs or with BMP‐2 and hMSCs but not pregrown into bone‐like tissue. Bone‐related outcomes were improved when compared with the scaffold controls implanted without BMP‐2. These studies illustrate the potential use of slow degrading silk fibroin 3‐D scaffolds loaded with BMP‐2, in combination with hMSCs, in osteogenesis studies in vitro and in vivo, and provide a new range of material properties for these applications. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Effect of changes of pH on the anaerobic/aerobic transformations of biological phosphorus removal in wastewater fed with a mixture of propionic and acetic acids
Authors: Chen Yinguang , Gu Guowei
Published: April 2006

Most studies on the transformation of enhanced biological phosphorus removal have used acetic acid as the carbon source and focused on the anaerobic phase. In this paper the anaerobic and aerobic transformations of phosphorus removal microorganisms at various pH values were investigated with wastewater containing 3.14 mM C propionic acid and 1.56 mM C acetic acid. It was observed that the influence of acidic pH on the concentrations of mixed‐liquor suspended solids and biomass was stronger than that of basic pH, and the maximal cell growth appeared at pH 7.6. The observed uptake rate of propionic acid was much faster than that of acetic acid at all pH values investigated, and both were affected by pH. The anaerobic transformations of polyhydroxyalkanoates and glycogen linearly decreased with increasing pH from 6.6 to 8.6, and a greater glycogen transformation correlated to greater polyhydroxyalkanoate transformation in both anaerobic and aerobic stages. Further studies revealed that at pH 6.6 and 8.6 the overall phosphorus release and uptake was low and there was no net phosphorus removal, although the initial phosphorus release was high. However, when the pH was controlled at pH 7.1 and 7.6, a phosphorus removal efficiency of 97.03% and 96.43% was achieved, respectively, which was greater than that of 87.46% at uncontrolled pH. Copyright © 2006 Society of Chemical Industry
Fermentation characteristics of a low‐oxygen inducible hmp promoter system in Bacillus subtilis LAB1886
Authors: Han Mu Ri , Shang Long‐An , Chang Ho Nam , Han Se Jong , Kim Yun Chul , Lee Jong Won
Published: April 2006

In an attempt to find a low‐cost promoter system which could be used for producing recombinant proteins, a low oxygen inducible hmp promoter system in Bacillus subtilis (LAB1886) was characterized by studying the effects of cell density (OD600), glucose concentration, pH, dissolved oxygen (DO) level, nitrate and nitrite concentration on cell growth and β‐galactosidase expression. The optimal cultivation strategy was found to be to grow the cells in the presence of nitrate to OD600 = 0.2 at a high DO level (80%), and then to induce the hmp promoter by lowering the DO level to 1–2%. As a result, the specific β‐galactosidase activity increased continuously to the maximal value of 1750 Miller Units. Nitrite, as the apparent inducer of the hmp promoter, was produced from nitrate reduction, and had profound effects on cell growth and β‐galactosidase expression. Copyright © 2006 Society of Chemical Industry
Effect on down syndrome screening performance of adjusting for marker levels in a previous pregnancy
Authors: Wald Nicholas J. , Barnes Isobel M. , Birger Ruthie , Huttly Wayne
Published: April 2006

Objectives

In prenatal screening for Down syndrome, serum marker values can be adjusted using values from a previous pregnancy to avoid the problem of women having a high chance of recurrent false‐positive results. We investigate the effect of such adjustment on overall screening performance.

Methods

Monte Carlo simulation was used to investigate the effect of this adjustment on five widely used screening tests for Down syndrome (Triple, Quadruple, Combined, serum Integrated, Integrated tests).

Results

Adjustment for screening marker values (expressed in multiples of the median, (MoM)) in a previous pregnancy improved screening performance. The detection rate for a 1% false‐positive rate (FPR) increased from 54 to 59% with the Triple test, from 63 to 68% with the Quadruple test, from 71 to 75% for the Combined test, from 71 to 76% for the serum Integrated test, and from 85 to 88% for the Integrated test. The FPR for an 85% detection rate decreased from 10 to 7.9%, 7.1 to 4.9%, 4.9 to 3.7%, 4.7 to 2.9% and 1.1 to 0.7% respectively for the five tests. Among women who have had a false‐positive result in a previous pregnancy, adjustment substantially lowers the false‐positive rate, for example, from 19 to 7.3% with the Combined test using a 1 in 250 risk cut‐off.

Conclusion

MoM adjustment for values in a previous pregnancy improves overall screening performance and substantially reduces the high recurrent false‐positive rate. This adjustment can be routinely applied in screening programmes through the screening software used to interpret a woman's screening results. Copyright © 2006 John Wiley & Sons, Ltd.
Less‐ordered lamellar structure of intercalated poly(L‐lactide)/organo‐modified montmorillonite hybrids
Authors: Nam Pham Hoai , Ninomiya Naoya , Fujimori Atsuhiro , Masuko Toru
Published: April 2006

Hybrids of poly(L‐lactide)/organophilic clay (PLACHs) have been prepared via a melt‐compounding process using poly(L‐lactide) (PLLA) and different contents of surface‐treated montmorillonite modified with dimethyl dioctadecyl ammonium‐salt. The crystalline structures of PLLA and dispersion states of clay particles in those PLACHs were investigated by use of wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, transmission electron microscopy (both cross section and replication modes), and polarized optical microscopy. Those structures are viewed from the conformational changes of PLLA chains in the space of a few nanometer widths between silicate galleries to crystalline lamellae of several nanometer thicknesses, and spherulitic textures more than micrometer sizes. After annealing treatments at 115°C for 1 hr, the PLACHs formed coarse‐grained spherulitic textures with 40 μm diameter composed of less‐ordered and fragmented lamellae, caused by the reduced mobility of the PLLA chain due to the dispersed clay particles in the PLLA matrix and the intercalation of the PLLA chains in the silicate galleries. The formation of the interfibril structure accompanied by the fragmented lamellae among the dispersed clay particles was examined. POLYM. ENG. SCI., 46:703–711, 2006. © 2006 Society of Plastics Engineers
Group hydrotherapy versus group land‐based treatment for chronic low back pain
Authors: Sjogren Tracey , Long Nerida , Story Ian , Smith Jenni
Published: April 2006

Sixty subjects with chronic low back pain (LBP) were sequentially allocated to either hydrotherapy treatment or land treatment groups in order of presentation. Subjects acted as their own controls for a period of three weeks, after which they attended their respective group sessions twice weekly for six weeks. Twenty‐eight subjects from each group attended all treatment and assessment sessions. Results indicated that both groups improved significantly in functional ability and in decreasing pain levels. Thoracolumbar mobility did not improve significantly in either group. Overall there was no significant difference found between the two types of treatment, although results should be viewed as encouraging for the advocates of both hydrotherapy and land‐based exercise as a treatment for chronic LBP. Copyright © 1997 Whurr Publishers Ltd.
Preparation of arrays of metallic nanoparticles exhibiting coulomb blockade at room temperature: an approach based on the self‐organization of metal‐loaded diblock‐copolymers
Authors: Dietrich Christof , Koslowski Berndt , Weigl Frank , Ziemann Paul
Published: April 2006

The self‐organization of HAuCl4 loaded poly (styrene)‐block‐poly (2‐vinylpyridine) (PS‐b‐P2VP) diblock‐copolymers resulting in hexagonally ordered arrays of Au nanoparticles is exploited to prepare a system exhibiting single electron charging effects at room temperature. For this purpose, the metallic nanoparticles are deposited on top of an Al2O3 tunnel barrier separating them from a Niobium thin film backelectrode grown on a c‐cut Sapphire substrate. The single electron system is completed by the metal tip of a scanning tunneling microscope (STM), which is positioned right above the nanoparticle and serves as the second electrode. The STM additionally allowed taking current‐voltage I (V) characteristics revealing a large gap around zero bias typical of a Coulomb blockade. This interpretation is supported by the good agreement between experimental I (V) curves and their theoretical description. Copyright © 2006 John Wiley & Sons, Ltd.
The differential impact of social-pension income on household poverty alleviation in three South African ethnic groups
Authors: FERREIRA MONICA
Published: April 2006

Social pension programmes play a key role in old-age support systems through their ability to reach vulnerable older persons. Pension income helps to sustain households affected by extreme poverty and vulnerability, by providing resources for spending that protects against vulnerability, and thereby they facilitate economic and social development. Under apartheid, South Africa's citizens were categorised according to race, and persons classified as Asian, black and coloured (mixed race) had less access to the opportunities and resources available to whites. Parity in the amount of social pension benefits paid to beneficiaries in the different ethnic categories was achieved only in 1993. The Non-Contributory Pensions and Poverty Study (NCPPS), conducted in Brazil and South Africa, has assessed the impact of social pension income on household poverty alleviation. This paper draws on the findings of the South African survey to analyse the differential effects of pension income on household poverty alleviation in three ethnic-geographic groups. Its data show a pervasive social and economic gradient of disadvantage among the groups, with rural-black households being most disadvantaged, urban-coloured households least disadvantaged, and urban-black households in between. The impact of pension income on household poverty alleviation has a similar pattern. The paper concludes with a discussion of the implications of the findings for the achievement of equity through informed policy interventions.
Gadolinium scandate thin films as an alternative gate dielectric prepared by electron beam evaporation
Authors: Wagner M. , Heeg T. , Schubert J. , Lenk St. , Mantl S. , Zhao C. , Caymax M. , De Gendt S.
Published: April 2006

Gadolinium scandate thin films deposited on silicon substrates using electron beam evaporation were investigated. Measurements with Rutherford backscattering spectrometry, high temperature x-ray diffraction, x-ray reflectometry, transmission electron microscopy, and atomic force microscopy were performed. A stoichiometric transfer of material from the source to the substrate in high vacuum could be demonstrated. Homogeneous, amorphous, and smooth films (root mean square surface roughness <1Å) stable up to 1000°C were obtained. Electrical characterization of capacitor stacks revealed a dielectric constant of ≈23, C-V curves with small hysteresises and low leakage current densities (770μA∕cm2 for a capacitance equivalent thickness of 1.5nm).
Polarization state-dependent stress effect on the dielectric properties of lead zirconate titanite thin films
Authors: Kang H. D. , Song W. H. , Sohn S. H. , Jin H. J. , Lee S. E. , Chung Y. K.
Published: April 2006

We performed a bending experiment on a thin Pb(Zr,Ti)O3 (PZT) film prepared by chemical solution deposition. The changes of dielectric constant under stress were measured upon sweeping the electric field applied across the PZT film. It was found that depending on the strength of the electric field and thereby on the polarization state of the ferroelectric film, stress acts as a promoter as well as an obstructor for the polarization. An explanation for the abnormal dielectric behavior is given based on the domain wall motion and the reorientation of polarization state.
Functional Characterization of Homo- and Heteromeric Channel Kinases TRPM6 and TRPM7
Authors: Li Mingjiang , Jiang Jianmin , Yue Lixia
Published: April 2006

TRPM6 and TRPM7 are two known channel kinases that play important roles in various physiological processes, including Mg2+ homeostasis. Mutations in TRPM6 cause hereditary hypomagnesemia and secondary hypocalcemia (HSH). However, whether TRPM6 encodes functional channels is controversial. Here we demonstrate several signature features of TRPM6 that distinguish TRPM6 from TRPM7 and TRPM6/7 channels. We show that heterologous expression of TRPM6 but not the mutant TRPM6S141L produces functional channels with divalent cation permeability profile and pH sensitivity distinctive from those of TRPM7 channels and TRPM6/7 complexes. TRPM6 exhibits unique unitary conductance that is 2- and 1.5-fold bigger than that of TRPM7 and TRPM6/7. Moreover, micromolar levels of 2-aminoethoxydiphenyl borate (2-APB) maximally increase TRPM6 but significantly inhibit TRPM7 channel activities; whereas millimolar concentrations of 2-APB potentiate TRPM6/7 and TRPM7 channel activities. Furthermore, Mg2+ and Ca2+ entry through TRPM6 is enhanced three- to fourfold by 2-APB. Collectively, these results indicate that TRPM6 forms functional homomeric channels as well as heteromeric TRPM6/7 complexes. The unique characteristics of these three channel types, TRPM6, TRPM7, and TRPM6/7, suggest that they may play different roles in vivo.
Haplotype associations of 90 rare alleles from the National Marrow Donor Program®®
Authors: Kempenich J. H. , Setterholm M. , Maiers M.
Published: April 2006

The National Marrow Donor Program maintains an HLA database of over 4.1 million US adult volunteers, 43,000 cord blood units, and 111,000 patients from which we identified 1,999,424 samples having allele‐level HLA‐A, HLA‐B, or HLA‐DRB1 results. We analyzed 811 rare alleles reported at a frequency of less than 1 in 50,000 in this study pool and found strong predicted haplotype associations for 90 of them. The data set includes the number of times the allele was seen, the predicted haplotypes, and the racial or ethnic groups in which it was identified. This information can be helpful in designing search strategies for patients with rare alleles requiring hematopoietic stem cell therapy.
THE MOBILIZATION OF HUMAN RESOURCES AS AN EFFECT OF THE DEPLETION OF ENVIRONMENTAL AND SOCIAL ASSETS
Authors: Bartolini Stefano , Bonatti Luigi
Published: April 2006

In this paper, the growth process is not fed by the accumulation of productive assets (physical and/or human capital, knowledge etc.), but by the depletion of environmental or social resources, which induces individuals to increase their labor supply in order to consume more of the market goods that substitute for the depleted resources. Hence, production is expanded, thus eroding the resources’ ability to regenerate, which decreases with aggregate production. Within this context, the ‘green’ net national product is derived and it is shown how a regulatory authority should manage the resources for achieving Pareto‐optimality.
RELIABILITY ANALYSIS OF COMPLEX SYSTEMS BASED ON THE LOSSES FROM FAILURES
Authors: TODINOV M. T.
Published: April 2006

The conventional reliability analysis is based on the premise that increasing the reliability of a system will decrease the losses from failures. In this paper it is demonstrated that increasing the reliability of the system does not always mean decreasing the losses from failures. An inappropriate increase of the reliability of the system may lead to a simultaneous increase of the losses from failure. In other words, a system reliability improvement, which is disconnected from the losses from failure does not necessarily reduce the losses from failures.

An efficient discrete-event simulation model and algorithm have been proposed for reliability analysis based on the losses from failure for production systems with complex topology. The model links reliability with losses from failures. A new algorithm has also been developed for system reliability analysis related to productions systems based on multiple production units where the absence of critical failure means that at least m out n production units are working.

The parametric study conducted on the basis of the developed models revealed that a dual-control production system is characterized by enhanced production availability, which increases with increasing the number of production units in the system. A production unit from a dual-control production system including multiple production units is characterized by a larger availability compared to a production unit from a dual-control production system including a single production unit.

The proposed approach has been demonstrated by comparing the losses from failures and the net present values of two competing design topologies: one based on a single-channel control and the other based on a dual-channel control. The proposed models have been successfully applied and tested for reliability value analysis of productions systems in deepwater oil and gas production.

It is also argued that the reliability allocation in a production system should be done to maximize the net profit/value obtained from the system. Consequently, a method for setting reliability requirements and reliability allocation maximizing the net profit by minimizing the sum of the capital costs and the expected losses from failures has been proposed. Reliability allocation which maximizes the net profit in case of a system consisting of blocks arranged in series is achieved by determining for each block individually, the reliabilities of the components which minimize the sum of the capital costs and the expected losses from failures.
The Relationship between Plasma BNP Level and the Myocardial Phosphocreatine/Adenosine Triphosphate Ratio Determined by Phosphorus-31 Magnetic Resonance Spectroscopy in Patients with Dilated Cardiomyopathy
Authors: Chida Koichi , Otani Hiroki , Kohzuki Masahiro , Saito Haruo , Kagaya Yutaka , Takai Yoshihiro , Takahashi Shoki , Yamada Shogo , Zuguchi Masayuki
Published: April 2006

The purpose of this study was to evaluate the correlation between the plasma B-type natriuretic peptide (BNP) level and the myocardial phosphocreatine/adenosine triphosphate ratio determined using rapid phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in patients with dilated cardiomyopathy (DCM). Thirteen DCM patients, who had slight or moderate heart failure, were examined. The plasma BNP was measured on a day close to the rapid 31P-MRS study. 31P-MRS measurements were conducted with a 1.5-T MR instrument. The plasma BNP levels tended to be correlated negatively with the myocardial phosphocreatine/adenosine triphosphate, although the correlation did not reach statistical significance (r = –0.54, p =0.06). By contrast, the log of the plasma BNP levels was correlated negatively with the myocardial phosphocreatine/adenosine triphosphate (r = –0.73, p < 0.01). Our results indicate that the myocardial energy metabolism evaluated using 31P-MRS tends to be correlated with the severity of heart failure and left ventricular dysfunction estimated using the plasma BNP levels in DCM patients. This paper provides additional information regarding the relationship between the BNP and myocardial energy metabolism in DCM patients.
The Anti-Ischemic Effect of Metoprolol in Patients with Chronic Angina Pectoris Is Gender-Specific
Authors: Cocco Giuseppe , Chu David
Published: April 2006

Several gender-specific differences in cardiovascular diseases are known and pharmacokinetics of β-blockers shows relevant sex-specific differences. The plasma levels of metoprolol, for example, are higher in women compared to men. However, randomized studies have shown that metoprolol has little or no greater reduction in the mortality of women following myocardial infarction. We tested the hypothesis that metoprolol might have significant gender-specific effects in patients with chronic angina pectoris. Body weight of women was slightly (–9%) less than that of men and the daily dose of metoprolol was similar in both groups. Thus, according to pharmacokinetics women should have obtained higher plasma levels of this drug and the ensuing pharmacologic effects of metoprolol should have been greater. Our results do not confirm this assumption. Metoprolol reduced the frequency of angina episodes and the consumption of nitroglycerin tablets to a similar extent in both sexes. However, the pretreatment hemodynamic profiles confirmed the existence of gender-specific differences: women had significantly higher heart rate and blood pressure both at rest and during exercise. Since both groups were comparable in age, comorbidities, and medications, the existing difference is likely to be due to gender-specificity. The hemodynamic differences persisted during therapy with metoprolol: resting heart rate, blood pressure and rate pressure product were reduced to a greater extent in men. During cycloergometry, there was a slight difference in the time of onset of ST depression and time of onset of angina, which were slightly higher in men, but probably because of the limited number of cases, the difference between men and women did not reach significance. On the other hand, with metoprolol the duration of exercise and, in parallel, the number of metabolic equivalents was significantly greater in males than in females. Thus in spite of a presumed greater plasma concentration of metoprolol in women, we found a significant difference in anti-ischemic effect in favor of men. We conclude that metoprolol might exert a significantly greater therapeutic effect on stress-induced angina pectoris in men than in women and this difference should be taken into account when prescribing this β-blocker.
Stochastic Forcing of the North Atlantic Wind-Driven Ocean Circulation. Part II: An Analysis of the Dynamical Ocean Response Using Generalized Stability Theory
Authors: Chhak Kettyah C. , Moore Andrew M. , Milliff Ralph F. , Branstator Grant , Holland William R. , Fisher Michael
Published: April 2006

As discussed in Part I of this study, the magnitude of the stochastic component of wind stress forcing is comparable to that of the seasonal cycle and thus will likely have a significant influence on the ocean circulation. By forcing a quasigeostrophic model of the North Atlantic Ocean circulation with stochastic wind stress curl data from the NCAR CCM3, it was found in Part I that much of the stochastically induced variability in the ocean circulation is confined to the western boundary region and some major topographic features even though the stochastic forcing is basinwide. This can be attributed to effects of bathymetry and vorticity gradients in the basic state on the system eigenmodes. Using generalized stability theory (GST), it was found in Part I that transient growth due to the linear interference of nonnormal eigenmodes enhances the stochastically induced variance. In the present study, the GST analysis of Part I is extended and it is found that the patterns of wind stress curl that are most effective for inducing variability in the model have their largest projection on the most nonnormal eigenmodes of the system. These eigenmodes are confined primarily to the western boundary region and are composed of long Rossby wave packets that are Doppler shifted by the Gulf Stream to have eastward group velocity. Linear interference of these eigenmodes yields transient growth of stochastically induced perturbations, and it is this process that maintains the variance of the stochastically induced circulations. Analysis of the large-scale circulation also reveals that the system possesses a large number of degrees of freedom, which has significant implications for ocean prediction. Sensitivity studies show that the results and conclusions of this study are insensitive and robust to variations in model parameters and model configuration.
The Relative Importance of Wind Strength and Along-Shelf Bathymetric Variations on the Separation of a Coastal Upwelling Jet
Authors: Castelao Renato M. , Barth John A.
Published: April 2006

A high-resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on the wind strength and the horizontal scale of the bank. Experiments were run using several wind forcing magnitudes and submarine banks with different geometries, so as to explore a wide range of the flow strength as measured by the Rossby number (Ro) and the ratio of the squares of the internal Rossby radius of deformation and curvature of the topography as denoted by the Burger number (Bu). The intensity of the jet separation is strongly dependent on both parameters, with maximum separation with increasing Ro and Bu close to 1, when large amounts of upwelled water are exported toward deeper waters. For small Bu, separation is minimal and independent of Ro. For high Ro, the degree of separation decreases at large Bu since the bank acts only as a small perturbation to the flow. Term balances in the along-shelf momentum equation reveal that the primary balance over the bank is between the nonlinear and the ageostrophic terms. In an asymmetric bank, the radius of curvature in the upstream half of the bank dominates in terms of determining the offshore deflection of a water particle at the surface. The asymmetry increases the cross-isobath transport but not the offshore deflection of the jet.
Resisting corporate communications: Insights into folk linguistics
Authors: Llewellyn Nick , Harrison Alan
Published: April 2006

Focus group research is used to examine how employees read corporate communications, supplying empirical evidence of an apparently resilient and shared anti-management discourse at the shopfloor level. The main contribution of the article lies in showing how such traditional attitudes are reproduced through employees' cynical readings of corporate communications. The article complements more conventional modes of discourse analysis by exploring how employees analyse text; how they identify discursive controversies and find evidence of ‘conniving’ management. Considering such processes reveals points of interest about how employees' folk linguistic competencies are locally deployed in ways that reproduce class-based logics and sentiments.