The random barrier-crossing problem

This paper addresses the time-variant reliability analysis of structures with random resistance or random system parameters. It deals with the problem of a random load process crossing a random barrier level. The implications of approximating the arrival rate of the first overload by an ensemble-crossing rate are studied. The error involved in this so-called ""ensemble-crossing rate"" approximation is described in terms of load process and barrier distribution parameters, and in terms of the number of load cycles. Existing results are reviewed, and significant improvements involving load process bandwidth, mean-crossing frequency and time are presented. The paper shows that the ensemble-crossing rate approximation can be accurate enough for problems where load process variance is large in comparison to barrier variance, but especially when the number of load cycles is small. This includes important practical applications like random vibration due to impact loadings and earthquake loading. Two application examples are presented, one involving earthquake loading and one involving a frame structure subject to wind and snow loadings. (C) 2007 Elsevier Ltd. All rights reserved.

A Separation Principle for the Continuous-Time LQ-Problem With Markovian Jump Parameters

In this paper, we devise a separation principle for the finite horizon quadratic optimal control problem of continuous-time Markovian jump linear systems driven by a Wiener process and with partial observations. We assume that the output variable and the jump parameters are available to the controller. It is desired to design a dynamic Markovian jump controller such that the closed loop system minimizes the quadratic functional cost of the system over a finite horizon period of time. As in the case with no jumps, we show that an optimal controller can be obtained from two coupled Riccati differential equations, one associated to the optimal control problem when the state variable is available, and the other one associated to the optimal filtering problem. This is a separation principle for the finite horizon quadratic optimal control problem for continuous-time Markovian jump linear systems. For the case in which the matrices are all time-invariant we analyze the asymptotic behavior of the solution of the derived interconnected Riccati differential equations to the solution of the associated set of coupled algebraic Riccati equations as well as the mean square stabilizing property of this limiting solution. When there is only one mode of operation our results coincide with the traditional ones for the LQG control of continuous-time linear systems.

New simple and efficient heuristics for the uncapacitated single allocation hub location problem

Hub-and-spoke networks are widely studied in the area of location theory. They arise in several contexts, including passenger airlines, postal and parcel delivery, and computer and telecommunication networks. Hub location problems usually involve three simultaneous decisions to be made: the optimal number of hub nodes, their locations and the allocation of the non-hub nodes to the hubs. In the uncapacitated single allocation hub location problem (USAHLP) hub nodes have no capacity constraints and non-hub nodes must be assigned to only one hub. In this paper, we propose three variants of a simple and efficient multi-start tabu search heuristic as well as a two-stage integrated tabu search heuristic to solve this problem. With multi-start heuristics, several different initial solutions are constructed and then improved by tabu search, while in the two-stage integrated heuristic tabu search is applied to improve both the locational and allocational part of the problem. Computational experiments using typical benchmark problems (Civil Aeronautics Board (CAB) and Australian Post (AP) data sets) as well as new and modified instances show that our approaches consistently return the optimal or best-known results in very short CPU times, thus allowing the possibility of efficiently solving larger instances of the USAHLP than those found in the literature. We also report the integer optimal solutions for all 80 CAB data set instances and the 12 AP instances up to 100 nodes, as well as for the corresponding new generated AP instances with reduced fixed costs. Published by Elsevier Ltd.

The single machine earliness and tardiness scheduling problem: lower bounds and a branch-and-bound algorithm

This paper addresses the single machine scheduling problem with a common due date aiming to minimize earliness and tardiness penalties. Due to its complexity, most of the previous studies in the literature deal with this problem using heuristics and metaheuristics approaches. With the intention of contributing to the study of this problem, a branch-and-bound algorithm is proposed. Lower bounds and pruning rules that exploit properties of the problem are introduced. The proposed approach is examined through a computational comparative study with 280 problems involving different due date scenarios. In addition, the values of optimal solutions for small problems from a known benchmark are provided.

Photochemical heat-shock response in common bean leaves as affected by previous water deficit

The heat sensitivity of photochemical processes was evaluated in the common bean (Phaseolus vulgaris) cultivars A222, A320, and Carioca grown under well-watered conditions during the entire plant cycle (control treatment) or subjected to a temporal moderate water deficit at the preflowering stage (PWD). The responses of chlorophyll fluorescence to temperature were evaluated in leaf discs excised from control and PWD plants seven days after the complete recovery of plant shoot hydration. Heat treatment was done in the dark (5 min) at the ambient CO2 concentration. Chlorophyll fluorescence was assessed under both dark and light conditions at 25, 35, and 45 degrees C. In the dark, a decline of the potential quantum efficiency of photosystem II (PSII) and an increase in minimum chlorophyll fluorescence were observed in all genotypes at 45 degrees C, but these responses were affected by PWD. In the light, the apparent electron transport rate and the effective quantum efficiency of PSII were reduced by heat stress (45 degrees C), but no change due to PWD was demonstrated. Interestingly, only the A222 cultivar subjected to PWD showed a significant increase in nonphotochemical fluorescence quenching at 45 degrees C. The common bean cultivars had different photochemical sensitivities to heat stress altered by a previous water deficit period. Increased thermal tolerance due to PWD was genotype-dependent and associated with an increase in potential quantum efficiency of PSII at high temperature. Under such conditions, the genotype responsive to PWD treatment enhanced its protective capacity against excessive light energy via increased nonphotochemical quenching.

A common matrix metalloproteinase (MMP)-2 polymorphism affects plasma MMP-2 levels in subjects environmentally exposed to mercury

Mercury (Hg) exposure is associated with disease conditions, including cardiovascular problems. Although the mechanisms implicated in these complications have not been precisely defined yet, matrix metalloproteinases (MMPs) may be involved. The gene encoding MMP-2 presents genetic polymorphisms which affect the expression and activity level of this enzyme. A common polymorphism of MMP-2 gene is the C(-1306)T (rs 243865), which is known to disrupt a Sp1-type promoter site (CCACC box), thus leading to lower promoter activity associated with the T allele. This study aimed at examining how this polymorphism affects the circulating MMP-2 levels and its endogenous inhibitor, the tissue inhibitor of metalloproteinase-2 (TIMP-2) in 210 subjects environmentally exposed to Hg. Total blood and plasma Hg concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). MMP-2 and TIMP-2 concentrations were measured in plasma samples by gelatin zymography and ELISA, respectively. Genotypes for the C(-1306)T polymorphism were determined by Taqman (R) Allele Discrimination assay. We found a positive association (p = 0.0057) between plasma Hg concentrations and MMP-2/TIMP-2 (an index of net MMP-2 activity). The C(-1306)T polymorphism modified MMP-2 concentrations (p = 0.0465) and MMP-2/TIMP-2 ratio (p = 0.0060) in subjects exposed to Hg, with higher MMP-2 levels been found in subjects carrying the C allele. These findings suggest a significant interaction between the C(-1306)T polymorphism and Hg exposure, possibly increasing the risk of developing diseases in subjects with the C allele. (C) 2011 Elsevier B.V. All rights reserved.

Watkins and the Pragmatic Problem of Induction

Watkins proposes a neo-Popperian solution to the pragmatic problem of induction. He asserts that evidence can be used non-inductively to prefer the principle that corroboration is more successful over all human history than that, say, counter-corroboration is more successful either over this same period or in the future. Watkins's argument for rejecting the first counter-corroborationist alternative is beside the point. However, as whatever is the best strategy over all human history is irrelevant to the pragmatic problem of induction since we are not required to act in the past, and his argument for rejecting the second presupposes induction.

Common multiples of complete graphs

A graph H is said to divide a graph G if there exists a set S of subgraphs of G, all isomorphic to H, such that the edge set of G is partitioned by the edge sets of the subgraphs in S. Thus, a graph G is a common multiple of two graphs if each of the two graphs divides G.

On the nonlinear Neumann problem with critical and supercritical nonlinearities

We investigate the solvability of the Neumann problem (1.1) involving a critical Sobolev exponent. In the first part of this work it is assumed that the coeffcients Q and h are at least continuous. Moreover Q is positive on overline Omega and lambda > 0 is a parameter. We examine the common effect of the mean curvature and the shape of the graphs of the coeffcients Q and h on the existence of low energy solutions. In the second part of this work we consider the same problem with Q replaced by - Q. In this case the problem can be supercritical and the existence results depend on integrability conditions on Q and h.

The intersection problem for star designs

We determine those triples (m, II, k) of integers for which there are two m-star designs on the same n-set having exactly k stars in common.

Women's satisfaction with general practice consultations

Objective: To determine women's satisfaction with general practice services. Design: Cross-sectional postal questionnaire conducted during April to September 1996 (part of the baseline survey of the Australian Longitudinal Study on Women's Health). Participants: Women aged 18-22 (n=14739), 45-49 (n=14013) and 70-74 (n=12941) years, randomly selected from the Medicare database, with oversampling of women from rural and remote areas. Main outcome measures: Frequency of use of general practice services; satisfaction with the most recent visit to a general practitioner (CP), prevalence of selected symptoms; preference for a female doctor. Results: The most recent visit to a GP was rated overall as good, very good or excellent by more than 80% of women, with increasing levels of satisfaction with increasing age of the women. However, satisfaction was lower for waiting room time and cost of the visit. A third of the young and middle-aged women living in rural and remote areas were dissatisfied with the cost of the visit. Young women were more likely to prefer a female doctor, and many were dissatisfied with their GP's skills at explaining their problem and giving them a chance to give an opinion and ask questions. The most prevalent symptoms for all women included headaches and tiredness, and many were not satisfied with the health services available to help them deal with these symptoms. Conclusions: Australian women have high levels of satisfaction with GP consultations. However, more effective strategies may be needed to improve communication with younger women, and there is an unmet need for services to help all women deal with some common symptoms. Dissatisfaction with cost of services and women's preference for female doctors have implications for future health policy.

Dysregulated hematopoiesis and a progressive neurological disorder induced by expression of an activated form of the human common beta chain in transgenic mice

Previously we described activating mutations of h beta(c), the common signaling subunit of the receptors for the hematopoietic and inflammatory cytokines, GM-CSF, IL-3, and IL-5. The activated mutant, h beta(c)FI Delta, is able to confer growth factor-independent proliferation on the murine myeloid cell line FDC-P1, and on primary committed myeloid progenitors. We have used this activating mutation to study the effects of chronic cytokine receptor stimulation. Transgenic mice were produced carrying the h beta(c)FI Delta cDNA linked to the constitutive promoter derived from the phosphoglycerate kinase gene, PGK-1. Transgene expression was demonstrated in several tissues and functional activity of the mutant receptor was confirmed in hematopoietic tissues by the presence of granulocyte macrophage and macrophage colony-forming cells (CFU-GM and CFU-M) in the absence of added cytokines. All transgenic mice display a myeloproliferative disorder characterized by splenomegaly, erythrocytosis, and granulocytic and megakaryocytic hyperplasia. This disorder resembles the human disease polycythemia vera, suggesting that activating mutations in h beta(c) may play a role in the pathogenesis of this myeloproliferative disorder. In addition, these transgenic mice develop a sporadic, progressive neurological disease and display bilateral, symmetrical foci of necrosis in the white matter of brain stem associated with an accumulation of macrophages. Thus, chronic h beta(c) activation has the potential to contribute to pathological events in the central nervous system.

The common tetratricopeptide repeat acceptor site for steroid receptor-associated immunophilins and Hop is located in the dimerization domain of hsp90

Structurally related tetratricopeptide repeat motifs in steroid receptor-associated immunophilins and the STI1 homolog, Hop, mediate the interaction with a common cellular target, hsp90, We have identified the binding domain in hsp90 for cyclophilin 40 (CyP40) using a two-hybrid system screen of a mouse cDNA library. All isolated clones encoded the intact carboxyl terminus of hsp90 and overlapped with a common region corresponding to amino acids 558-724 of murine hsp84, The interaction was confirmed in vitro with bacterially expressed CyP40 and deletion mutants of hsp90 beta and was delineated further to a 124-residue COOH-terminal segment of hsp90, Deletion of the conserved MEEVD sequence at the extreme carboxyl terminus of hsp90 precludes interaction with CyP40, signifying an important role for this motif in hsp90 function. We show that CyP40 and Hop display similar interaction profiles with hsp90 truncation mutants and present evidence for the direct competition of Hop and FK506-binding protein 52 with CyP40 for binding to the hsp90 COOH-terminal region. Our results are consistent with a common tetratricopeptide repeat interaction site for Hop and steroid receptor associated immunophilins within a discrete COOH-terminal domain of hsp90. This region of hsp90 mediates ATP-independent chaperone activity, overlaps the hsp90 dimerization domain, and includes structural elements important for steroid receptor interaction.

International tourists and road safety in Australia: developing a national research and management programme

Motor vehicle crashes are the leading cause of injury death for international tourists. This makes road safety an important issue for tourism authorities. Unfortunately, as it is in other areas of tourist health, the common response from the travel and tourism industry is to remain silent about this problem and to leave any mishaps in the hands of insurers. At the same time, but for different reasons, international tourists are not usually targeted for road safety initiatives by transport authorities. Given that there are considerable 'hidden' costs associated with international tourists and motor vehicle crashes, the topic should be of concern to both tourism and transport groups. This paper examines issues concerned with driving in unfamiliar surroundings for international visitors in Australia, and proposes a national research and management programme to guide policy and planning in the area. (C) 1999 Elsevier Science Ltd. All rights reserved.

Myeloproliferative disorder and leukaemia in mice induced by different classes of constitutive mutants of the human IL-3/IL-5/GM-CSF receptor common beta subunit

Several constitutively active mutant forms of the common β subunit of the human IL-3, IL-5 and GM-CSF receptors (hβc), which enable it to signal in the absence of ligand, have recently been described. Two of these, V449E and I374N, are amino acid substitutions in the transmembrane and extracellular regions of hβc, respectively. A third, FIΔ, contains a 37 amino acid duplication in the extracellular domain. We have shown previously that when expressed in primary murine haemopoietic cells, the extracellular mutants confer factor-independence on cells of the neutrophil and monocyte lineages only, whereas V449E does so on all cell types of the myeloid and erythroid compartments. To study the in vivo effects and leukaemic potential of these mutants, we have expressed all three in mice by bone marrow reconstitution using retrovirally infected donor cells. Expression of the extracellular mutants leads to an early onset, chronic myeloproliferative disorder marked by elevations in the neutrophil, monocyte, erythrocyte and platelet lineages. In contrast, expression of V449E leads to an acute leukaemia-like syndrome of anaemia, thrombocytopaenia and blast cell expansion. These data support the possibility that activating mutations in hβc are involved in haemopoietic disorders in man.