Infinite Span Research Articles

Downtime of the service station in M/G/1 queueing system with repairable service station

In this paper the downtime of the service station in the M/G/1 queueing system with repairable service station is discussed. In the following, some new results are obtained: (a) the distribution and the mean value of the downtime during the generalized service time; (b) the distribution and the mean value of the downtime during the system busy period; (c) the mean value of the downtime per unit-time for infinite time span; (d) some asymptotic formulas for calculating the mean value of the downtime during the time interval (0, t]. These results would be of interest to reliability analysts.

Malignant transformation of human fibroblasts by ionizing radiation.

As one step in developing an assay for quantifying the induction of malignant transformation of human cells by ionizing radiation, we exposed cells from a non-tumorigenic, infinite life span, near-diploid fibroblast strain MSU-1.1 to 4.35 Gy 60Co radiation and assayed them for focus formation. The mean frequency of foci in the irradiated population was 6 x 10(-7) cells assayed. No foci were found in the control cells. Of four focus-derived cell strains studied in detail, two produced malignant tumours within 3-7 weeks. The other two did not produce tumours during the 12-month period of study. The tumours from one strain were classified as sarcomas composed exclusively of spindle-shaped cells. Tumours from the other strain were sarcomas consisting of a mixed population of round and spindle cells. Immunoprecipitation analysis of the status of the p53 gene in the focus-derived strains, using a mutant-specific anti-body (Pab240) and an antibody that recognizes both mutant and wild-type p53 protein (Pab421), showed that the tumorigenic strains were completely devoid of p53 protein. One non-tumorigenic strain expressed wild-type p53 protein, and the other expressed a lower molecular weight form of the protein. Karyotypic analysis showed that the tumour-derived cells from one tumorigenic strain had lost one copy of chromosome 6, 14, 16 and 17. The tumour-derived cells from the second strain had lost one copy of chromosome 7, 13, 14 and 17 and part of chromosome 6, as well as part of the other copy of chromosome 7 and 17. These results suggest that the common loss of one copy of chromosome 14, 17 and part of 6 plays a causal role in the malignant transformation of these cells. Furthermore, the results indicate that it will be possible to develop a system that uses near-diploid human fibroblasts to quantify radiation-induced malignant transformation.

Optimal control of a finite dam with a sample path constraint

In this paper, we discuss the 2-stage output procedure of a finite dam under the condition that water must be released by a fixed time. From this standpoint, the reservoir model we consider is subject to a sample path constraint and has a more general cost function than the earlier contributions. We analytically derive explicit formulas for the long-run average and the expected total discounted costs for an infinite time span and numerically calculate the optimal control policy. Finally, the optimal policy is compared with one by Zuckerman [1] and the effect of the fixed release time is discussed further.

Malignant transformation of human fibroblast strain MSU-1.1 by v-fes requires an additional genetic change.

To determine whether the v-fes oncogene can malignantly transform human fibroblasts that have acquired an infinite life span and are partially growth-factor-independent, we transfected cell strain MSU-1.1 with a plasmid containing the v-fes oncogene and a bacterial histidinol dehydrogenase gene. Of the 60 independent histidinol-resistant clones isolated and assayed for v-fes expression using a fes-specific monoclonal antibody, 6 were found to express the v-fes protein at a detectable level. When progeny cells from these 6 clones were further characterized, 3 of the 6 clonal populations exhibited a significant increase in the ability to form medium-sized colonies in agarose, but none were tumorigenic in athymic mice. However, when the 6 populations were propagated for many generations, the same 3 populations acquired the ability to form very large colonies in agarose ( > or = 100 microM in diameter) at a frequency of 2% to 17%, and formed malignant tumors in athymic mice. This suggests that an additional genetic change required for malignant transformation had been spontaneously acquired in 3 of the v-fes -transformed cell strains. To determine whether the change or changes were the equivalent of an activated sis or ras proto-oncogene, we transfected the v-fes oncogene into derivative strains of MSU-1.1 that express a transfected v-sis, c-H-ras or c-N-ras oncogene, but that do not form tumors, and assayed the v-fes-expressing transfectants for tumorigenicity. The results showed that when complemented either by a ras oncogene expressed at a somewhat enhanced level or by the v-sis oncogene, v-fes can supply the additional change required for malignant transformation.

Numerical solution of a nonlinear problem of the motion of a plane hydrofoil beneath the free surface of an ideal incompressible fluid

A nonlinear problem of the motion of a hydrofoil of infinite span beneath the free surface of an ideal incompressible fluid with gravity is studied. The stream function is used as the dependent variable. Iterative algorithms for small and large Froude numbers based upon solving a linear boundary value problem in each step with subsequent updating of the shape of the free boundary are proposed. Typical predictions are given for a symmetric profile at different values of the submersion depth, the Froude number and the angle of attack. The free surface and streamlines shapes are shown. The dependence of the lift on the submersion depth for motion through fluid layers of different thickness is presented.

Transfection of amyc gene as a means of generating infinite life span human fibroblast strains

Human fibroblasts in culture have never been found to transform spontaneously into immortal cells. In an effort to generate an infinite life span cell strain from foreskin-derived normal diploid fibroblasts, we transfected the cells with a plasmid carrying a v-myc oncogene linked to theneo gene, or with a control vector carrying theneo gene, and selected drug-resistant clones. A clone that expressed the v-myc protein was propagated to the end of its life span, with periodic cryogenic storage of the progeny. The population went into crisis at the same time as cells from the control population and eventually senesced. However, while the cells were senescing, viable-appearing clones were noted. The cells of these clones continued to multiply, very slowly at first but eventually at a faster rate. Analysis showed that these cells have a diploid karyotype that has remained stable throughout more than 200 population doublings since their sibling cells senesced. Molecular analysis showed that the infinite life span cells are, indeed, derived from the cells used for transfection, and that they continue to express the v-myc protein.

A generalized sequential preventive maintenance policy for repairable systems with general random minimal repair costs

A generalized sequential preventive maintenance (PM) policy for repairable systems with general random minimal repair costs is proposed and analysed. After each (planned or unplanned) preventive maintenance, the system has a different failure distribution and the failure rate function increases with the number of preventive maintenances carried out. The criterion for the optimal policy is to minimize the expected cost per unit time for an infinite time span. It is shown that under certain reasonable assumptions, sequential preventive maintenance policy has unique solutions. Various special cases are considered.

The solution of evolutionary games using the theory of Hamilton-Jacobi equations

A dynamical model of a non-antagonistic evolutionary game for two coalitions is considered. The model features an infinite time span and discounted payoff functionals. A solution is presented using differential game theory. The solution is based on the construction of a value function for auxiliary antagonistic differential games and uses an approximate grid scheme from the theory of generalized solutions of the Hamilton-Jacobi equations. Together with the value functions the optimal guaranteeing procedures for control on the grid are computed and the Nash dynamic equilibrium is constructed. The behaviour of trajectories generated by the guaranteeing controls is investigated. Examples are given.

Heat transfer to blunt-edged swept wings at angle of attack in hypersonic flow

An approximate analytic solution is obtained for the relative heat fluxes on the lateral surface of swept wings of infinite span in a hypersonic viscous gas flow at angles of attack and yaw. The accuracy of the relations obtained is estimated on the basis of a comparison with numerical solutions.

Analysis of the multistep process of carcinogenesis using human fibroblasts.

Normal human cells in culture have never been neoplastically transformed by carcinogen exposure. One possible explanation is that the life span of such cells is too short for them to acquire the necessary changes. To test this hypothesis, we needed normal human cells with a greatly extended or an infinite life span. We transfected the v-myc gene and a selectable marker into normal human fibroblasts, identified a drug-resistant clone expressing v-myc protein, and passaged the progeny of the clone until they senesced. A few cells continued to proliferate and gave rise to a diploid, infinite life span cell strain, MSU-1.0, that has normal growth control and is nontumorigenic in athymic mice. Analysis showed that one more genetic change, in addition to unregulated expression of the v-myc gene, was involved in generating MSU-1.0 cells. They spontaneously gave rise to a variant strain, designated MSU-1.1, that grows more rapidly and is less dependent on exogenous growth factors. Analysis showed that at least two additional changes were involved in generating this cell strain. It has a stable karyotype composed of 45 chromosomes, including two markers. Transfection of specific oncogenes was used to determine the number and nature of additional changes required to transform MSU-1.1 cells into malignant cells. Analysis indicated that two changes were involved, but no change in karyotype. Exposure of MSU-1.1 cells to a single carcinogen treatment, followed by selection for cells with the characteristics of oncogene-transformed MSU-1.1 cells also yielded malignant human cells. We conclude that malignant transformation of normal human fibroblasts requires six or seven genetic changes, some of which involve suppressor genes.

Failure of infinite life span human cells from different immortality complementation groups to yield finite life span hybrids.

The observation that fusion of infinite life span cells with finite life span cells produces hybrid cells with finite life spans led to the conclusion that an infinite life span in culture is a recessive trait resulting from loss of the function of a gene or genes that contribute to an active program for cellular senescence. Furthermore, finding that certain pairs of infinite life span cells, when fused to one another, can complement each other to yield finite life span hybrids allowed 30 infinite life span cell lines to be assigned to four immortality complementation groups (Pereira-Smith and Smith, 1988, Proc. Natl. Acad. Sci. U.S.A., 85:6042). In the present study, we fused a chromosomally stable, near diploid, morphologically normal, infinite life span cell strain, designated MSU-1.1, with its normal, finite life span, precursor cell strain and obtained finite life span hybrids, as expected if infinite life span in culture is a recessive trait. However, 14 of the 14 hybrids from our fusions of MSU-1.1 cells with representative cell lines from each of the four immortality complementation groups, and 38 of the 39 hybrids from our fusions of infinite life span cells that have been reported to complement each other, failed to exhibit finite life spans. This result suggests that infinite life span cells cannot complement each other to yield finite life span hybrids. In examining this unexpected result, we obtained evidence that long-term dual drug selection can be deleterious to hybrid cells even though they carry resistance markers for both drugs, indicating that the cell death of such hybrids observed in other studies may have resulted from the cytotoxic effect of long-term drug selection, rather than from senescence.

Free and Forced Vibrations of Periodic Multispan Beams

In this study, the following two topics are considered for uniform multispan beams of both finite and infinite lengths with rigid transversal and elastic rotational constraints at each support: (a) free vibration and the associated frequencies and mode shapes; (b) forced vibration under a convected harmonic loading. The concept of wave propagation in periodic structures of Brillouin is utilized to investigate the wave motion at periodic supports of a multispan beam. A dispersion equation and its asymptotic form is obtained to determine the natural frequencies. For the special case of zero rotational spring stiffness, an explicit asymptotic expression for the natural frequency is also given. New expressions for the mode shapes are obtained in the complex form for multispan beams of both finite and infinite lengths. The orthogonality conditions of the mode shapes for two cases are formulated. The exact responses of both finite and infinite span beams under a convected harmonic loading are obtained. Thus, the position and the value of each peak in the harmonic response function can be determined precisely, as well as the occurrence of the so-called coincidence phenomenon, when the response is greatly enhanced.

Free and Forced Vibrations of Periodic Multispan Beams

In this study, the following two topics are considered for uniform multispan beams of both finite and infinite lengths with rigid transversal and elastic rotational constraints at each support: (a) free vibration and the associated frequencies and mode shapes; (b) forced vibration under a convected harmonic loading. The concept of wave propagation in periodic structures of Brillouin is utilized to investigate the wave motion at periodic supports of a multispan beam. A dispersion equation and its asymptotic form is obtained to determine the natural frequencies. For the special case of zero rotational spring stiffness, an explicit asymptotic expression for the natural frequency is also given. New expressions for the mode shapes are obtained in the complex form for multispan beams of both finite and infinite lengths. The orthogonality conditions of the mode shapes for two cases are formulated. The exact responses of both finite and infinite span beams under a convected harmonic loading are obtained. Thus, the position and the value of each peak in the harmonic response function can be determined precisely, as well as the occurrence of the so-called coincidence phenomenon, when the response is greatly enhanced.

Continuous time inventory control for wiener process demand

This paper discusses a continuous time inventory system without backlogging allowed under the condition that the demand follows a Wiener process. We propose the explicit formula of the expected total discounted cost for an infinite time span by applying the familiar technique of optimal stopping problem. Further, it is shown that the asymptotic value of the expected total discounted cost by perturbation of the discount rate gives the long-run average cost. Finally, the optimal inventory policies, which are given as the optimal stock levels minimizing the expected total discounted and the long-run average costs, are numerically obtained and compared with ones in the deterministic inventory system. It is made apparent that the discount rate and the diffusion parameter of the demand process are very sensitive for the optimal inventory policies.

滑走平板が造る波の研究について-II : 無限幅滑走平板上の圧力分布計測実験

滑走平板が造る波の研究について-II : 無限幅滑走平板上の圧力分布計測実験

Analysis of Two Length-Based Mortality Models Applied to Bounded Catch Length Frequencies

Abstract We performed an assessment of the length-based total mortality model of Beverton and Holt, assuming that catch length-frequency distributions in tropical artisanal fisheries are constrained by (1) the selective properties of multiple gears used and (2) the spatiotemporal availabilities of certain size classes of fish to operationally restricted fleets. Positive bias always resulted with the Beverton and Holt estimator of Z (total mortality); this estimator assumes an infinite exploitable life span. Estimates of Z were unreasonably biased when exploitable life spans were 50% or less of the biological life span of the species considered in the analyses. Biases were larger at lower levels of fishing mortality rates. We developed a new method from a truncated equation for average fish length. It considers length at first capture and the maximum retainable length actually observed in the fishery catch. The method has no explicit solution for Z, so we used numerical methods to provide its solution. The...

On backup policies for hard computer disks

Abstract The present study discusses backup policies for the files stored in a hard computer disk or hard computer disks. Two periodical backup policies are proposed both of which make a backup copy of files in a hard disk at age T , where ‘age’ refers to the elapsed time since the previous operation of making a backup copy or recovering from the hard disk failure. Under Policy I, all the files in the hard disk(s) are copied to the floppy disks or the magnetic tapes at every backup time. Under Policy II, a copy of the files created and/or updated since the previous backup time is added to the backup floppy disks or the magnetic tapes at the current backup time. For each policy, the expected cost per unit time over an infinite time span is formulated as an objective function. The existence of an optimal value of T minimizing the expected cost is examined. Numerical examples are also shown to illustrate the proposed backup policies. It is shown under Policy I that there always exists a positive finite optimal backup time, while the conditions under which an optimal backup time exists are clarified for Policy II.

Supersonic laminar flow on the windward surface of yawed wings of infinite span over a broad range of Reynolds numbers

Supersonic laminar flow on the windward surface of yawed wings of infinite span over a broad range of Reynolds numbers

滑走平板が造る波の研究について-I : 無限幅滑走平板の造波現象の実験

滑走平板が造る波の研究について-I : 無限幅滑走平板の造波現象の実験

Characteristics of an infinite life span diploid human fibroblast cell strain and a near-diploid strain arising from a clone of cells expressing a transfectedv- myc oncogene

Diploid human fibroblasts were transfected with a plasmid carrying av- myconcogene linked to the neo gene or with a vector control carrying a neo gene. Drug-resistant clones were isolated and subcultured as needed. All populations went into crisis and eventually senesced. But while they were senescing, viable-appearing clones were noted among the progeny of a transfected population that expressed thev- myc oncogene. After several months, these cells began replicating more rapidly. Karyotype analysis indicated that they were clonally derived since all of them had 45 chromosomes, including 2 marker chromosomes. This cell strain was designated MSU-1.1. Similar analysis showed that cells from an earlier passage were diploid. These cells were designated MSU-1.0. Both strains have undergone more than 200 population doublings since their siblings senesced, without any change in chromosome complement. Both strains express thev- mycprotein and have the same integration site for the transfectedv- mycand neo genes. The MSU-1.0 cells cannot grow without exogenously added growth factors. The MSU-1.1 cells grow moderately well under the same conditions and grow to a higher saturation density than MSU-1.0 cells. Since the chance of human cells acquiring an infinite life span in culture is very rare, the data suggest that MSU-1.1 cells are derived from MSU-1.0 cells. The expression ofv- myc is probably required for acquisition of an infinite life span, since this phenotype did not develop in populations not expressing this oncogene. However, expression ofv- myc is clearly not sufficient, since all of the progeny of the clone that gave rise to the MSU-1.0 cells expressed this oncogene, but the vast majority of them senesced.