bluuebunny/crossref_metadata_2025_split huggingface dataset:
On identifiability in the autopsy model of reliability theory
Authors: Antoine Robin , Doss Hani , Hollander Myles 
Published: April 2006

A coherent system is observed until it fails. At the instant of system failure, the set of failed components and the failure time of the system are noted. The failure times of the components are not known. We consider whether the component life distributions can be determined from the distributions of the observed data.Meilijson (1981) gave a condition on the structure of the system that was sufficient for the identifiability of the component distributions, under the assumption that the component life distributions are continuous and have common essential extrema. Nowik (1990) gave necessary and sufficient conditions for identifiability under the more restrictive condition that the component distributions have atoms at their common essential infimum and are mutually absolutely continuous. We give a necessary condition for identifiability, which we show to be equivalent to Nowik's condition, under the assumption that the distributions are continuous and strictly increasing. We derive a sufficient condition for identifiability, more general than Meilijson's, for the case in which the component distributions are assumed to be analytic. We also show that our necessary condition for identifiability is both necessary and sufficient when the component life distributions are assumed to belong to certain parametric families.
Convexity results for single-server queues and for multiserver queues with constant service times
Authors: Harel Arie 
Published: April 2006

We show that the waiting time in queue and the sojourn time of every customer in the G/G/1 and G/D/c queue are jointly convex in mean interarrival time and mean service time, and also jointly convex in mean interarrival time and service rate. Counterexamples show that this need not be the case, for the GI/GI/c queue or for the D/GI/c queue, for c ≧ 2. Also, we show that the average number of customers in the M/D/c queue is jointly convex in arrival and service rates.These results are surprising in light of the negative result for the GI/GI/2 queue (Weber (1983)).
Darwin's log: a toy model of speciation and extinction
Authors: Aldous David 
Published: April 2006

Stochastic models for the origin and extinction of species have been rather neglected in applied probability. As an alternative to modelling speciation and extinction as intrinsically random, I shall describe and show simulations of a rulebased model. This involves mathematical representations of notions such as genetic type of species, environmental niche, fitness of a species in a niche, and adaptation. There are underlying random mechanisms for changes of niche sizes and for disconnection and reconnection of geographical regions, and these ultimately drive the evolution of species.Other approaches to mathematical modelling of evolution are briefly mentioned.
Optimization of 1,3‐propanediol production by novel recombinant Escherichia coli using response surface methodology
Authors: Zhang Xiaomei , Li Yin , Zhuge Bin , Tang Xueming , Shen Wei , Rao Zhiming , Fang Huiying , Zhuge Jian 
Published: April 2006

AbstractResponse surface methodology was used to optimize 1,3‐propanediol production by a novel recombinant Escherichia coli JM109 (pHsh‐dhaB‐yqhD). The optimal fermentation parameters for enhanced 1,3‐propanediol yield were found to be: glycerol 61.8 g L−1, yeast extract 6.2 g L−1, Vitamin B12 0.049 g L−1 and fermentation time 30 h. Subsequent experimental trials confirmed the validity of the model. These optimal fermentation conditions in the cultivation flask culture led to a 1,3‐propanediol concentration of 43.1 g L−1 and a conversion rate of 69.7% (g g−1). A maximum 1,3‐propanediol concentration of 41.1 g L−1 was achieved in a 5 L fermenter using the optimized parameters. Copyright © 2006 Society of Chemical Industry
The incidence of pancytopenia in patients taking leflunomide alone or with methotrexate
Authors: McEwen John , Purcell Patrick M. , Hill Richard L. , Calcino Lisa J. , Riley Cathy G. 
Published: April 2006

AbstractPurposeTo estimate the incidence of pancytopenia in patients taking leflunomide with or without methotrexate in Australia.MethodsReview of spontaneous reports to the Australian Adverse Drug Reactions Advisory Committee (ADRAC); estimation of incidence using national prescription reimbursement data; concomitant exposure to methotrexate was estimated using three sources of information.ResultsADRAC received 11 reports of pancytopenia (meeting predefined criteria) associated with the use of leflunomide during its first 31 months of marketing. In nine reports, the patients were also taking methotrexate. Estimates of incidence in patients taking leflunomide alone ranged from 1 in 3698 to 1 in 4582 patients exposed; for patients also taking methotrexate the estimates ranged from 1 in 575 to 1 in 822.ConclusionsUse of methotrexate with leflunomide increases the risk of pancytopenia compared with use of leflunomide alone. The haematological toxicity of the combination requires further study. Copyright © 2006 Commonwealth of Australia, published by John Wiley & Sons, Ltd.
Synthesis of novel ionic polymers containing arsonic acid group
Authors: García‐Serrano J. , Herrera A. M. , Pérez‐Moreno F. , Valdez M. A. , Pal U. 
Published: April 2006

AbstractSynthesis of ortho‐ and para‐acryloylaminophenylarsonic acids (o‐AAPHA and p‐AAPHA) monomers and their homopolymers, useful as ion‐exchange materials, are reported. Both the monomers and homopolymers are synthesized with >90% yield. The structures of the new compounds are determined by NMR and FTIR spectroscopy. Molecular weights of the polymers are determined from light scattering measurements and found to be Mw = 38,759 g/mol for o‐AAPHA polymer and Mw = 31,347 g/mol for p‐AAPHA polymer. Good thermal stability of the new compounds derived from their intra‐ or intermolecular hydrogen bondings suggests their applications as proton‐exchange membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1627–1634, 2006
The Jet Propulsion Laboratory Autonomous Helicopter Testbed: A platform for planetary exploration technology research and development
Authors: Montgomery James F. , Johnson Andrew E. , Roumeliotis Stergios I. , Matthies Larry H. 
Published: April 2006

AbstractThe Jet Propulsion Laboratory Autonomous Helicopter Testbed (AHT), an aerial robot based upon a radio‐controlled model helicopter, provides a small low‐cost platform for developing and field testing new technologies needed for future space missions. The AHT helps cover the test space in a complementary fashion to other methods, such as rocket sleds or parachute drops. The AHT design and implementation is presented as well as experimental results and milestones achieved since its creation in 2001. In addition, technologies we are developing and testing are described. These include image‐based hazard detection and avoidance algorithms for safe landing in dangerous terrain and an extended Kalman filter that augments inertial navigation with image‐based motion estimates to enable pin‐point landing. © 2006 Wiley Periodicals, Inc.
A lateral growth mode leading to successive rotation of crystallographic orientation
Authors: Shu Da‐Jun , Li Da‐Wei , Pan Wei , Li Hong‐Min , Peng Ru‐Wen , Wang Mu , Ming Nai‐Ben 
Published: April 2006

AbstractA general theory of heteroepitaxial lateral growth of nanocrystallites via successive nucleation at the concave corner of the nanocrystallite and the substrate was developed. The theory treats the existence of a rotational instability of crystallographic orientation induced by the imbalance of surface/interface energy. From the theory it can be concluded that the crystallographic orientation may rotate continuously, sustained either by consecutive changes of facets on the growth front or by periodic modulation of surface energy of the substrate. Copyright © 2006 John Wiley & Sons, Ltd.
Enzymatic pathways involved in the generation of endothelin‐1(1–31) from exogenous big endothelin‐1 in the rabbit aorta
Authors: Tirapelli Carlos R , Fecteau Marie‐Helene , Honore Jean‐Claude , Legros Eurode , Gobeil Fernand , D'orleans‐Juste Pedro 
Published: April 2006

We investigated whether blood vessels contribute to the production of ET‐1(1–31) from exogenous big endothelin‐1 (BigET‐1) in the rabbit and assessed which enzymes are involved in this process.
Vascular reactivity experiments, using standard muscle bath procedures, showed that BigET‐1 induces contraction in endothelium‐intact rabbit aortic rings. Preincubation of the rings with phosphoramidon, CGS35066 or thiorphan reduced BigET‐1‐induced contraction. Conversely, chymostatin did not affect BigET‐1‐induced contraction.
Thiorphan and phosphoramidon, but not CGS35066 or chymostatin, reduced ET‐1(1–31)‐induced contraction. None of the enzymatic inhibitors affected the contraction afforded by ET‐1.
BQ123‐, but not BQ788‐, selective antagonists for ETA and ETB receptors, respectively, produced concentration‐dependent rightward displacements of the ET‐1(1–31) and ET‐1 concentration–response curves.
By the use of enzymatic assays, we found that the aorta, as well as the heart, lung, kidney and liver, possess a chymase‐like activity.
Enzyme immunoassays detected significant levels of Ir‐ET‐1(1–31) in bathing medium of aortas after the addition of BigET‐1 (30 nM). Neither thiorphan nor chymostatin altered the levels of Ir‐ET‐1(1–31). Conversely, the levels of Ir‐ET‐1(1–31) were increased in the presence of phosphoramidon. This marked increase of the 31‐amino‐acid peptide was abolished when phosphoramidon and chymostatin were added simultaneously.
The major new finding of the present work is that the rabbit aorta generates ET‐1(1–31) from exogenously administered BigET‐1. Additionally, by measuring the production of ET‐1(1–31), we showed that a chymase‐like enzyme is involved in this process when ECE and NEP are inhibited by phosphoramidon. Our results also suggest that ET‐1(1–31) is an alternate intermediate in the production of ET‐1 following BigET‐1 administration. Finally, we showed that NEP is the predominant enzymatic pathway involved in the cleavage of ET‐1(1–31) to a bioactive metabolite that will act on ETA receptors to induce contraction in the rabbit aorta.

British Journal of Pharmacology (2006) 148, 527–535. doi:10.1038/sj.bjp.0706735
The identification of three novel MICA alleles by sequence‐based typing
Authors: Quiroga I. , Sweeney D. , Sutton P. M. , Ahmad T. , Walton R. , Barnardo M. C. N. M. , Fuggle S. V. 
Published: April 2006

AbstractDuring a study of MICA frequency in a healthy population and a cohort of patients suffering with inflammatory bowel disease, three DNA samples produced unusual reactivity patterns using polymerase chain reaction sequence‐specific primers (PCR‐SSP). These samples were subsequently characterized by sequence‐based typing (SBT). Here, we report the sequence of these three novel MICA alleles.
Maternal medicine: Increased serum phosphodiesterase activity in women with pre‐eclampsia
Authors: Pinheiro da Costa BE , Scocco C , Poli de Figueiredo CE , Guimarães JA 
Published: April 2006

Objective  To measure the activity of serum phosphodiesterase (PDE) in pre‐eclampsia.Design  Case–control study.Setting  Nephrology Laboratory and Obstetrics Unit at São Lucas Hospital from Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.Sample  Twenty‐nine normal and 28 pregnant women with pre‐eclampsia.Methods  Serum was collected from women with pre‐eclampsia, at the time of diagnosis, and from gestation‐matched controls. Circulating PDE activity was assessed by measuring consumption of the substrate thymidine 5′‐monophosphate p‐nitrophenyl ester and expressed as PDE units/l.Main outcome measures  Serum PDE Activity.Results  Mean substrate consumption was higher in pre‐eclamptic condition (Vmax= 15.8 ± 1.4 versus 12.7 ± 0.9 U/L, P= 3.7 × 10−14).Conclusion  These data suggest that altered PDE activity may play a role in pre‐eclampsia endothelial dysfunction.
Basic science: Genes encoding bile acid, phospholipid and anion transporters are expressed in a human fetal cardiomyocyte culture
Authors: Gorelik J , Patel P , Ng’andwe C , Vodyanoy I , Diakonov I , Lab M , Korchev Y , Williamson C 
Published: April 2006

Objectives  To establish a human fetal cardiomyocyte culture and to investigate whether the genes that encode transporters that may influence influx or efflux of bile acids are expressed in human fetal cardiomyocytes.Design  Laboratory study.Setting  Imperial College London.Sample  Six fetal hearts were obtained at the time of termination of pregnancy at 12–13 weeks of gestation and used to generate primary human cardiomyocyte cultures.Methods  To confirm the presence of cardiomyocytes, the cells were incubated with monoclonal antibodies to sarcomeric α‐actinin and anticardiac myosin heavy chain. Real‐time reverse transcription polymerase chain reaction was used to establish whether transcripts of genes that may influence bile acid transport are present in the culture (NTCP, BSEP, MDR3, FIC1, MRP2, MRP3, OATP‐A, OATP‐C, OATP‐D, OATP‐E) and whether taurocholate administration alters messenger RNA (mRNA) expression.Main outcome measures  Relative mRNA expression of genes of interest.Results  Real‐time polymerase chain reaction demonstrated the presence of mRNA for BSEP, MDR3, FIC1, OATP‐C, OATP‐D and OATP‐E in fetal heart. Four transcripts remained in the cardiomyocyte culture (BSEP, MDR3, FIC1 and OATP‐D), and we demonstrated the influence of taurocholate on gene expression.Conclusions  We have developed an in vitro model of the fetal heart that may be used for studies of the cardiac effect of endobiotics, e.g. bile acids, or of specific agents that may be used to treat the mother or fetus in pregnancy.
Low-Level Mesocyclonic Concentration by Nonaxisymmetric Transport. Part I: Supercell and Mesocyclone Evolution
Authors: Gaudet Brian J. , Cotton William R. 
Published: April 2006

Abstract
An idealized simulation of a supercell using the Regional Atmospheric Modeling System (RAMS) was able to produce a low-level mesocyclone near the intersection of the forward- and rear-flank downdrafts. The creation of the low-level mesocyclone is similar to previous studies. After 3600 s, the low-level mesocyclone underwent a period of rapid intensification, during which its form changed from an elongated patch to a compact center. This transition was also accompanied by a sudden decrease in pressure (to 12 mb below that of the neighboring flow), and was found to occur even in the absence of nested grids.
It is shown that the stage of strong intensification does not begin aloft, as in the dynamic pipe effect, and then descend to the surface. Rather, the vortex is initiated near the surface, and then builds upward. The process is completed in 5 min, and the final vortex can be clearly distinguished from the larger-scale mesocyclone at the cloud base. The reduction of pressure can be explained as a consequence of the evacuation of mass in the horizontal convergence equation. This is in contrast to axisymmetric models of vortex intensification, which generally rely on the evacuation of mass in the vertical divergence equation. In the latter cases a positive horizontal convergence tendency is what initiates the concentrated vortex. However, nondivergent models prove that vorticity concentration can occur in the absence of any horizontal convergence. Here the concentration is associated with a negative horizontal convergence tendency.
A Mass-Conservative Semi-Implicit Semi-Lagrangian Limited-Area Shallow-Water Model on the Sphere
Authors: Lauritzen Peter H. , Kaas Eigil , Machenhauer Bennert 
Published: April 2006

Abstract
A locally mass conservative shallow-water model using a two-time-level, semi-implicit, semi-Lagrangian integration scheme is presented. The momentum equations are solved with the traditional semi-Lagrangian gridpoint form. The explicit continuity equation is solved using a cell-integrated semi-Lagrangian scheme, and the semi-implicit part is designed such that the resulting elliptic equation is on the same form as for the traditional semi-Lagrangian gridpoint system.
The accuracy of the model is assessed by running standard test cases adapted to a limited-area domain. The accuracy and efficiency of the new model is comparable to traditional semi-Lagrangian methods.
A note on Belyaev's limiting distribution of the intervals between losses in an n-server system
Authors: Tambouratzis D. G. 
Published: April 2006

SummaryThe aim of the present note is to give an alternative simpler proof to a result of Belyaev [1], namely that in a loss system of n servers with recurrent input and negative exponential service times the intervals between losses, suitably scaled to have constant mean, tend to a negative exponential distribution as n tends to infinity.
Inequalities for branching processes
Authors: Heathcote C. R. , Seneta E. 
Published: April 2006

SummaryIfF(s) is the probability generating function of a non-negative random variable, thenthfunctional iterateFn(s) =Fn–1(F(s)) generates the distribution of the size of the nth generation of a simple branching process. In general it is not possible to obtain explicit formulae for many quantities involvingFn(s), and this paper considers certain bounds and approximations. Bounds are found for the Koenigs-type iterates limn→∞m−n{1−Fn(s)}, 0 ≦s≦ 1 wherem=F′(1) < 1 andF′′(1) < ∞; for the expected time to extinctionand for the limiting conditional-distribution generating function limn→∞{Fn(s) −Fn(0)} [1 –Fn(0)]–1. Particular attention is paid to the caseF(s) = exp {m(s− 1)}.
Comparison of two treatments when there may be an initial effect
Authors: Scott Elizabeth L. 
Published: April 2006

Consider situations where the treatment may cause an initial effect and may also cause a long-range effect. We want to evaluate the treatment, or to compare two treatments, when the effect of treatment may result from the two distinct mechanisms, M1 and M2. We may wish to evaluate M1 and M2 separately, but we may also want to evaluate their combined effect M3. Examples are given and the general results are applied to the special case arising in weather modification studies and elsewhere: the possible effects are multiplicative and the distribution of non-zero variables is gamma with at most the scale parameter affected by treatment. An example demonstrates that the two components may be too weak to be judged significant while their sum is large and significant. The locally optimum C(α) test is used.There is a brief discussion of the power function of the tests. The asymptotic power agrees well, in general, by the results of the Monte Carlo simulation for the test Z3 of the combined effect. If the zero values are discarded and then Z2 employed, there is large bias in the power. The bias is more pronounced if the Wilcoxon, Mann–Whitney test is employed. Notice that the two effects under study may be acting in the same direction or they may be in opposition.
On the M/G/1 queue by additional inputs
Authors: Ott Teunis J. 
Published: April 2006

A single-server queueing system is studied, the input into which consists of the sum of two independent stochastic processes. One of these is an ‘M/G' type input process, the other a much more general process which need not be Markov. There are two types of busy period, depending on which arrival process started the busy period. Stochastic monotonicity results are derived and it is found that under a stationarity-like condition the probability of being in a busy period which started with an ‘M/G' arrival is independent of time and is the same it would be with the ‘M/G' process as only input process. Also, distributional results are obtained for the virtual waiting-time process, and these results are used to reduce the study of a single-server queueing system with as input the sum of independent ‘M/G' and ‘GI/G' input streams to the study of a related GI/G/1 queueing system.The purpose of this paper is to pave the way for a study of an M/G/1 queueing system with periodic arrivals of additional work, and for optimal scheduling of maintenance processes in certain real-time computer systems.
Optimal strategies for discovering new species in continuous time
Authors: Alsmeyer Gerold , Irle Albrecht 
Published: April 2006

Consider a population of distinct species Sj, j∈J, members of which are selected at different time points T1, T2,· ··, one at each time. Assume linear costs per unit of time and that a reward is earned at each discovery epoch of a new species. We treat the problem of finding a selection rule which maximizes the expected payoff. As the times between successive selections are supposed to be continuous random variables, we are dealing with a continuous-time optimal stopping problem which is the natural generalization of the one Rasmussen and Starr (1979) have investigated; namely, the corresponding problem with fixed times between successive selections. However, in contrast to their discrete-time setting the derivation of an optimal strategy appears to be much harder in our model as generally we are no longer in the monotone case.This note gives a general point process formulation for this problem, leading in particular to an equivalent stopping problem via stochastic intensities which is easier to handle. Then we present a formal derivation of the optimal stopping time under the stronger assumption of i.i.d. (X1, A1) (X2, A2), · ·· where Xn gives the label (j for Sj) of the species selected at Tn and An denotes the time between the nth and (n – 1)th selection, i.e. An = Tn – Tn–1. In the case where even Xn and An are independent and An has an IFR (increasing failure rate) distribution, an explicit solution for the optimal strategy is derived as a simple consequence.
On distributions having the almost-lack-of-memory property
Authors: Chukova S. , Dimitrov B. 
Published: April 2006

It is shown that random variables X exist, not exponentially or geometrically distributed, such thatP{X – b ≧ x | X ≧ b} = P{X ≧ x}for all x > 0 and infinitely many different values of b. A class of distributions having the given property is exhibited. We call them ALM distributions, since they almost have the lack-of-memory property. For a given subclass of these distributions some phenomena relating to service by an unreliable server are discussed.