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We consider coherent systems with independent and identically distributed components. While it is clear that the system’s life will be stochastically larger when the components are replaced with stochastically better components, we show that, in general, similar results may not hold for hazard rate, reverse hazard rate, and likelihood ratio orderings. We find sufficient conditions on the signature vector for these results to hold. These results are combined with other well-known results in the literature to get more general results for comparing two systems of the same size with different signature vectors and possibly with different independent and identically distributed component lifetimes. Some numerical examples are also provided to illustrate the theoretical results.
A critical branching process with immigration which evolves in a random environment is considered. Assuming that immigration is not allowed when there are no individuals in the population, we investigate the tail distribution of the so-called life period of the process, i.e. the length of the time interval between the moment when the process is initiated by a positive number of particles and the moment when there are no individuals in the population for the first time.
We consider point process convergence for sequences of independent and identically distributed random walks. The objective is to derive asymptotic theory for the largest extremes of these random walks. We show convergence of the maximum random walk to the Gumbel or the Fréchet distributions. The proofs depend heavily on precise large deviation results for sums of independent random variables with a finite moment generating function or with a subexponential distribution.
A matched case-control study was conducted in Bangladesh by enrolling case smallholdings of cattle affected with anthrax in the period of October 2010 to December 2014. The cases were initially reported by mass media and/or in surveillance reports from authorities concerned in the country. In total, 43 case smallholdings were enrolled. For each case, a control was matched by similarity in herd-size and rearing of animals, selected from a distantly located (within 3–10 km) place but within the same sub-district of the case farm. Data collected by administering a prototype questionnaire were analysed by matched-pair analysis and multivariable conditional logistic regression. Out of the 43 smallholdings, 41 were located in three adjoining districts: Pabna, Sirajganj and Tangail, apparently forming a spatial cluster, could be termed ‘anthrax hot spot’ in Bangladesh. Sick animal on farm or a nearby farm slaughtered in the recent past (odds ratio (OR) 12.2, 95% confidence interval (CI) 1.6–93.4, P = 0.016)), history of heavy rains occurring in the last 2 weeks preceding an outbreak (OR 13.1, 95% CI 1.2–147.1, P = 0.037) and disposing of dead animal into nearby water body (OR 11.9, 95% CI 1.0–145.3, P = 0.052) were independent risk factors for anthrax in cattle in the country.
We conducted a food consumption survey in the general adult population of 18 years and older in Germany to obtain data on the frequency of consumption of food items that caused foodborne disease outbreaks in the past. A total of 1010 telephone interviews were completed that queried the consumption of 95 food items in the 7-day period before the interview. Survey results were weighted to be representative. Six exemplary ‘high risk’ food items were consumed by 6% to 16% of the general population. These were raw ground pork: 6.5%; ‘Teewurst’ (=spreadable sausage-containing raw pork): 15.7%; unpasteurised milk consumed without prior heating: 9.0%; food items prepared with raw eggs: 9.8%; unheated sprouts or seedlings: 8.8% and frozen berries consumed without prior heating: 6.2%. Data from our food consumption survey were comparable to data obtained from control persons in case-control studies conducted during past foodborne disease outbreak investigations. We consider our survey an additional helpful tool that will allow comparison with food consumption data from case-patients obtained in exploratory, hypothesis-generating interviews early on in outbreak investigations, and which may assist in forming hypotheses regarding associations of illnesses with suspected food vehicles. This may facilitate and accelerate investigations of future foodborne disease outbreaks.
We review the basic theory of completely bounded (c.b.) and completely positive (c.p.) maps and prove the fundamental extension and factorization theorems about them.
This chapter is devoted to a proof that the Connes and Kirchberg questions are equivalent. We also formulate several equivalent variants of the conjectures, that somewhat complement the equivalence.
We describe the main properties of the bidual of a C*-algebra, that is also its enveloping von Neumann algebra. We define the tensor norms that naturally appear on a mixed pair formed of a C*-algebra and a von Neumann one, called the nor-norm and the bin-norm. This leads naturally to the notion of local reflexivity, which, in sharp contrast with the Banach space case, is not valid for all C*-algebras. Wegive explicit examples exhibiting that phenomenon, which is specific to the min-tensor product. Indeed, we show that the analogous defect disappears for the max-tensor product.
We prove here that the Connes and Kirchberg questions are equivalent to a different longstanding conjecture that circulated among Banach space theorists at least since the 1980’s if not sooner, namely the finite representability problem. The latter asks whether the predual of any von Neumann algebra is finitely representable in the trace class, or equivalent whether it embeds isometrically in an ultrapower (in the Banach space sense) of the trace class.
In the previous chapter we presented a statistical model for answering questions about a single population mean μ, when σ was known. Because σ usually is not known in practice, we present in this chapter a statistical model that is appropriate for answering questions about a single population mean when σ is not known. We also present two other statistical models that are appropriate for answering questions about the equality of two population means.
In the paper where he formulated his famous conjecture that the LLP implies the WEP, Kirchberg actually conjectured that the converse also held. This was disproved shortly later on. This boils down to showing that B=B(H) fails the LLP, or equivalently that the pair (B,B) is not nuclear. We give a presentation of the construction that leads to this negative answer. The main point is in terms of a sequence of constants C(n) indexed by an integer n, and the negative answercan be derived rather quickly from the fact that C(n) < n for some n. We give various methods that prove this fact, including the most complete one that shows using random unitary matrices that C(n) is equal to twice the square root of n-1, and hence is <1 for all n>2. In passing this gives us a nice example showing that exactness is not stable under extensions, i.e. we can have an ideal I in some A such that both I and A/I are exact but A is not exact.Since the pair (B,B) is not nuclear, this means thatthere are two distinct C* norms on the tensor product of B with itself. We describe the more recent proof that there are infinitely many, and actually a whole continuum, of distinct such norms.
In the situations of statistical inference that we have discussed regarding the mean and the variance, the dependent variable Y was tacitly assumed to be at the interval level of measurement. In addition, the statistical tests (e.g., t and F) required the assumptions of normality and, sometimes, homogeneity of variance of the parent population distributions.
This chapter presents Ozawa’s theorem that the minimal tensor product of B(H) with itself fails the WEP. The ingredients go through an investigation of the LLP for full crossed products of C*-algebras. Again the tools are either random matrices or deterministic examples related to property (T), but here it is crucial to work with unitary matrices associated to permutations.
In the previous chapter, we remarked that even when a strong linear correlation exists between two variables, X and Y, it may not be possible to talk about either one of them as the cause of the other. Even so, there is nothing to keep us from using one of the variables to predict the other. In making predictions from one variable to another, the variable being predicted is called the dependent variable and the variable predicting the dependent variable is called the independent variable. The dependent variable may also be referred to as the criterion or outcome while the independent variable may also be referred to as the predictor or regressor.
This chapter is an excursion into what could be called the local theoryof operator spaces. Here the main interest is on finite dimensional operator spaces and the degree of isomorphism of the various spaces is estimated using the c.b. analogue of the Banach-Mazur distance from Banach space theory. The main result is that the metric space formed of all the n-dimensional operator spaces equipped with the latter cb-distance is non separable for any n>2. This is in sharp contrast with the Banach space analogue which is a compact metric space.