Risk of conception

The highest mean number of sexual partners while in Spain was shown by females taking oral contraceptives (0.63, N = 8) followed by those not taking contraceptives but in the second half of their menstrual cycle (0.55 N = 11) and finally those in the first half of their menstrual cycle (0.50 N = 12). The differences, however, were not significant (ANOVA F 2 28 = 0.06 P = 0.94). Differences in risk of conception for the three groups were in any case probably minimal, given that the menstrual cycles of well over half of even the women not taking oral contraceptives would be anovulatory (Baker, unpublished data). 

This hint of a negative association with risk of conception for women in Phase I shown in Calahonda is shown much more strongly by women in the Manchester whole-ejaculate study. Here, the proportion of copulations that were EPCs decreased significantly as the risk of conception increased (Fig 2a). 

Figure 2. Summary of changes in female strategy for EPCs with stage of reproductive ontogeny. The women in the UK nation-wide survey were on average three years older than those in the Manchester whole-ejaculate study and were beginning to reproduce. Women in the nation-wide survey were (a) more likely to be unfaithful to their partner when the risk of conception was high and (b) showed an orgasm pattem/sperm retention pattern that favoured the EPC male rather than the partner. Women in the whole-ejaculate study were (a) less likely to be unfaithful when the risk of conception was high and (b) made no distinction between EPC males and current partner with respect to sperm retention. Nation-wide data from Baker and Beilis (1995).

Barrett, J. C. and Marshall, J. (1969). The risk of conception on different days of the menstrual cycle. Population Studies 23,455-461. 

Buck GM, Mendola P, Vena JE, et al. 1999. Paternal Lake Ontario fish consumption and risk of conception delay, New York State angler cohort. Environ Res 80 S13-S18. 

Products manufactured using concepts in UL Standard 746D provide quick verification of material identification, along with the assurance that acceptable blending or simple compounding operations are used that would not increase the risk of fire, electrical shock, or personal injury. 

Equilibrium phosphate concentration theory refutes the concept of blanket control determined by boiler pressure and operates each boiler system on a case-by-case basis. It seeks to strenuously avoid hideout-related problems and the subsequent risks of misdiagnosis. Operators are encouraged to explore the maximum operating tolerances before phosphate destabilization takes effect and hideout results, and to ensure... 

Critical ( -values for p - 0.05 are available. " - In lieu of using these tables, the calculated -values can be divided by the appropriate Student s t(f, 0.05) and V2 and compared to the reduced critical -vdues (see Table 1.12), and data file QRED TBL.dat. A reduced -value that is smaller than the appropriate critical value signals that the tested means belong to the same population. A fully worked example is found in Chapter 4, Process Validation. Data file MOISTURE.dat used with program MULTI gives a good idea of how this concept is applied. MULTI uses Table 1.12 to interpolate the cutoff point for p = 0.05. With little risk of error, this table can also be used fo = 0.025 and 0.1 (divide q by t(/, 0.025) /2 respectively t f, 0.1) V 2, as appropriate. 

The use of copolymers is essentially a new concept free from low-MW additives. However, a random copolymer, which includes additive functions in the chain, usually results in a relatively costly solution yet industrial examples have been reported (Borealis, Union Carbide). Locking a flame-retardant function into the polymer backbone prevents migration. Organophosphorous functionalities have been incorporated in polyamide backbones to modify thermal behaviour [56]. The materials have potential for use as fire-retardant materials and as high-MW fire-retardant additives for commercially available polymers. The current drive for incorporation of FR functionality within a given polymer, either by blending or copolymerisation, reduces the risk of evolution of toxic species within the smoke of burning materials [57]. Also, a UVA moiety has been introduced in the polymer backbone as one of the co-monomers (e.g. 2,4-dihydroxybenzophenone-formaldehyde resin, DHBF). 

But the main advantage of the SNR concept in modern analytical chemistry is the fact that the signal function is recorded continuously and, therefore, a large number of both background and signal values is available. As shown in Fig. 7.9, the principles of the evaluation of discrete and continuous measurement values are somewhat different. The basic measure for the estimation of the limit of detection is the confidence interval of the blank. It can be calculated from Eq. (7.52). For n = 10 measurements of both blank and signal values and a risk of error of a = 0.05 one obtains a critical signal-to-noise ratio (S/N)c = fo.95,9 = 1.83 and a = 0.01 (S/N)c = t0.99,9 = 2.82. The common value (S/N)c = 3 corresponds to a risk of error a = 0.05... 0.02 in case of a small number of measurements (n = 2... 5). When n > 6, a... 

The limit of detection (LoD) has already been mentioned in Section 4.3.1. This is the minimum concentration of analyte that can be detected with statistical confidence, based on the concept of an adequately low risk of failure to detect a determinand. Only one value is indicated in Figure 4.9 but there are many ways of estimating the value of the LoD and the choice depends on how well the level needs to be defined. It is determined by repeat analysis of a blank test portion or a test portion containing a very small amount of analyte. A measured signal of three times the standard deviation of the blank signal (3sbi) is unlikely to happen by chance and is commonly taken as an approximate estimation of the LoD. This approach is usually adequate if all of the analytical results are well above this value. The value of Sbi used should be the standard deviation of the results obtained from a large number of batches of blank or low-level spike solutions. In addition, the approximation only applies to results that are normally distributed and are quoted with a level of confidence of 95%. 

Based on this concept of correlation between high replication rate/high persistent mutation risk, Pike et al. (1983) formulated the hypothesis of breast tissue age and developed a mathematical model to predict the effects of exposure to ovarian hormones. This model incorporates reproductive and endocrine items related to breast cancer and is able to predict the relative risk of individual situations with results that are very close to those observed in clinical trials. According to this hypothesis, both the years of exposure and the circulating serum levels of estrogens are associated to short-term breast cancer risk in postmenopausal women (Toniolo et al. 1995). 

Before scientifically sound research can be performed on a subject, clear definitions must be set. Although, this may seem a logical step, Osborn (Osborn et al., 1988) highlighted that this has been a stumbling block for research in safety science since its inception. Definitions of concepts like accidents, incidents, near misses, risk, and safety, are known in the field of safety science, but interpreted differently in various situations. Unclear and ambiguous definitions lead to misinterpretations and confusion and must be avoided. Therefore, some general concepts used in safety science and the definitions used in this thesis are discussed in this Section. In the remainder of this thesis specific concepts will be defined where appropriate and can also be found in a list of acronyms and definitions presented in the beginning of this thesis. 

In this research, the main focus is safety in a chemical company handling hazardous substances. The risks of accidents or other events during processes involving hazardous substances (flammable, toxic, or explosive) or activities where extreme conditions are used (like high/low pressures or high/low temperatures), are subject of this research. Process safety is the absence of risk from events with these hazardous substances and activities with extreme conditions. Non-process safety or process risk is often measured by accidents, incidents and near misses and this concept will be discussed in the following sub-Section. 

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