By C. Dan. Jamestown College.
Distance The intensity of a radiation source order 30mg procardia with amex, and hence the radiation exposure order 30 mg procardia visa, varies inversely as the square of the distance from the source to the point of expo- sure. It is recommended that an individual should keep as far away as prac- tically possible from the radiation source. Procedures and radiation areas should be designed so that individuals conducting the procedures or staying in or near the radiation areas receive only minimum exposure. The G values are derived from the number of g-ray and x-ray emissions from the radionuclide, their energies, and their mass absorption coefﬁcients in air. The exposure rate X from an n-mCi radionuclide source at a distance d cm is given by a The G value of photon-emitting radionuclides can be calculated from the expres- sion G = 199ΣN Ei imi, where Ni is the fractional abundance of photons of energy Ei in MeV, and m is the mass absorption coefﬁcient (cm2/g) of photons of energy E in air. Shielding Various high atomic number (Z) materials that absorb radiations can be used to provide radiation protection. Because the ranges of a- and b- particles are short in matter, the containers themselves act as shields for these radiations. Therefore, highly absorbing material should be used for shielding of g-emitting sources, although for economic reasons, lead is most commonly used for this purpose. The radiopharmaceuti- cal dosages for patients should be carried in shielded syringes. Radionu- clides emitting b-particles should be stored in containers of low-Z material such as aluminum and plastic because in high-Z material, such as lead, they produce highly penetrating bremsstrahlung radiations. For example, 32P is a b− emitter and should be stored in plastic containers instead of lead containers. Activity It should be obvious that the radiation exposure increases with the inten- sity of the radioactive source. Therefore, one should not work unnecessarily with large quantities of radioactivity. Occupational workers including minors and pregnant women likely to receive in 1 year a dose in excess of 10% of the annual limit of exposure from the external radiation source 2. Three devices are used to measure the exposure of ionizing radiations received by an individual: the pocket dosimeter, the ﬁlm badge, and the thermoluminescent dosimeter. Film Badge The ﬁlm badge is most popular and cost-effective for personnel monitor- ing and gives reasonably accurate readings of exposures from b-, g- and x- radiations. The ﬁlm badge consists of a radiation-sensitive ﬁlm held in a plastic holder (Fig. Filters of different metals (aluminum, copper, and cadmium) are attached to the holder in front of the ﬁlm to differentiate 278 16. Filters of metals of different densities stop different energy radiations, thus discriminating exposures from them. After exposure the optical density of the developed ﬁlm is measured by a densitometer and compared with that of a calibrated ﬁlm exposed to known radiation. Film badges are usually changed monthly for each radiation worker in most institutions. The main disadvantage of the ﬁlm badge is the long waiting period (a month) before the exposed personnel know about their exposure. The ﬁlm badge also tends to develop fog resulting from heat and humidity, particularly when in storage for a long time, and this may obscure the actual exposure reading. The ﬁlm badges of all workers are normally sent to a commercial ﬁrm that develops and reads the density of the ﬁlms and sends back the report of exposure to the institution. When these crystals are exposed to radiation, electrons from the valence band are excited and trapped by the impurities in the forbidden band. If the radia- tion-exposed crystal is heated to 300°C to 400°C, the trapped electrons are raised to the conduction band; they then fall back into the valence band, emitting light. It should be noted that exposure resulting from medical procedures and background radiations are not included in occupational dose limits. These devices should be taken off during any medical procedures involv- ing radiation such as radiographic procedures and dental examinations, and also when leaving after the day’s work. Also radiation workers should not wear these badges for certain period of time after undergoing a diagnostic or therapeutic nuclear medicine procedure or radiation therapy permanent implant procedure. Dos and Don’ts in Radiation Protection Practice Do wear laboratory coats and gloves when working with radioactive materials. For iodine radionuclides, bioassay is performed by the thyroid uptake test within 72hr and at 14 days after handling the radioactivity. Radiation Regulations and Protection required for other radionuclides, depending on the amount and type of radionuclides. The suppliers require documentation of licensing of the user as to the types and limits of quantities of radioactive material before shipping.
However cheap procardia 30mg line, if a parametric test does not have a non-parametric equivalent then transformation is essential procardia 30 mg otc. However, difﬁculties arise sometimes in 44 Chapter 2 interpreting the results because few people think naturally in transformed units. For example, if length of stay is transformed by calculating its square root, the results of parametric tests will be presented in units of the square root of length of stay and will be more difﬁcult to interpret and to compare with results from other studies. Various mathematical formulae can be used to transform a skewed distribution to normality. When a distribution has a marked tail to the right-hand side, a logarithmic transformation of scores is often effective. Either base e or base 10 logarithms can be used but base 10 logarithms are a little more intuitive in that 0 = 1(10 ), 1∘ = 10 (101), 2 = 100 (102), and so on and are therefore a little easier to interpret and communicate. Since logarithm functions are deﬁned only for values greater than zero, any values that are zero in the data set will naturally be declared as invalid and registered as missing values in the transformed variable. In this data set, case 32 has a value of zero for length of stay and has been transformed to a system missing value for logarithmic length of stay. To ensure that all cases are included, for cases that have zero or negative values, a constant can be added to each value to ensure that the logarithmic transformation can be undertaken. This value can be subtracted again when the summary statistics are transformed back to original units. Descriptive statistics 45 Whenever a new variable is created, it should be labelled and its format adjusted. The log-transformed length of stay can be reassigned in Variable View by adding a label ‘Log length of stay’ to ensure that the output is self-documented. In addition, the number of decimal places can be adjusted to an appropriate number, in this case three and Measure can be changed to Scale. Once a newly transformed variable is obtained, its distribution must be checked again using the Analyze → Descriptive Statistics → Explore commands shown in Box 2. Explore Case Processing Summary Cases Valid Missing Total N Per cent N Per cent N Per cent Log length of stay 131 92. Also, the skewness value is now closer to zero, indicating no signiﬁcant skewness. The values for two standard deviations below and above the mean value, that is, 1. However, since case 32 was not transformed and was replaced with a system missing value, this case is now not listed as a lowest extreme value and the next extreme value, case 28 has been listed. In practice, peakness is not as important as skewness for deciding when to use parametric tests because deviations in kurtosis do not bias mean values. In the Tests of Normality table, the results of the Kolmogorov–Smirnov and Shapiro– Wilk tests indicate that the distribution remains signiﬁcantly different from a normal distribution at P = 0. Such gaps are a common feature of data distributions when the sample size is small but they need to be investigated when the sample size is large as in this case. Although log length of stay is not perfectly normally distributed, it will provide less biased P values than the original variable if parametric tests are used. Thus, the interpretation of the statistics should be undertaken using summary statistics of the transformed variable. If a variable has a skewed distribution, it is sometimes possible to transform the variable to normality using a mathematical algorithm so that the data points in the tail do not bias the summary statistics and P values, or the variable can be analysed using non-parametric tests. If the sample size is small, say less than 30, data points in the tail of a skewed distribu- tion can markedly increase or decrease the mean value so that it no longer represents the actual centre of the data. If the estimate of the centre of the data is inaccurate, then the mean values of two groups will look more alike or more different than the central values actually are and the P value to estimate their difference will be correspondingly reduced or increased. For this, statistics that describe the centre of the data and its spread are appropriate. Therefore, for variables that are normally distributed, the mean and the standard deviation are reported. In presenting descriptive statistics, no more than one decimal point greater than in the units of the original measurement should be used. The standard error of the mean provides an estimate of how precise the sample mean is as an estimate of the population mean. It is rare that this value would be below 30%, even in a child with severe lung disease. Therefore, the standard deviation is not an appropriate statistic to describe the spread of the data and parametric tests should not be used to compare the groups. If the lower estimate of the 95% range is too low, the mean will be an overestimate of the median value. If the lower estimate is too high, the mean value will be an underesti- mate of the median value. In this case, the median and inter-quartile range would provide more accurate estimates of the centre and spread of the data and non-parametric tests would be needed to compare the groups. Measuring changes in logarithmic data, with special reference to bronchial responsiveness. Two-sample t-tests are classically used when the outcome is a continuous variable and when the explanatory variable is binary.
The passages that I have discussed clearly suggest that buy procardia 30 mg amex, according to Aristotle generic 30 mg procardia free shipping, bodily conditions can be of inﬂuence on intellectual activities 77 On this expression see above, n. It is clear, however, that apart from incidental bodily states such as drunkenness or sleep (which may be characterised as disturbing agents, although the former is par fÅsin, the latter kat fÅsin), there are also more structural conditions such as the quality of the blood, age, the overall balance between warm and cold in the body and the quality of the skin. Variations in these structural conditions account for variations in intellectual capacities. The variations exist among different species, but also among individual members of one species or types within a species, such as dwarfs or melancholics. For the most part, these types represent ‘imperfect’ (tele±v) or ‘deformed’ (pephrwmnoi) groups of human beings with spe- cial characteristics due to their physical aberrations. However, some types (such as the malak»sarkoi) seem to represent special classes of humans whose distinctive characteristics are not to be regarded as deformations, but as variations within one species that may be either conducive, or harmful, or just neutral to the exercise of certain psychic powers. We hear very little about what the bodily conditions of a normal, success- ful operation of the intellectual powers are, but, as I have already said, there is good reason to assume that this is just because, in the writings that have survived, Aristotle simply does not have much reason to dwell on them. Our picture of Aristotle’s psycho-physiology is likely to remain very incom- plete – as is also indicated by the difﬁculties involved in piecing together his scattered remarks about physiological conditions such as pneuma, blood, and so forth. This has perhaps to do with his indebtedness to a medical tradition which supplied a lot of material which he could simply take for granted. As has already been demonstrated by Tracy – and is conﬁrmed by more recent work on Aristotle’s acquaintance with medical literature79 – this indebtedness is probably much greater than the scanty references to medical authorities in Aristotle’s works suggest. In this particular context, the Hippocratic work On Regimen comes to one’s mind, which in chapters 35 and 36 has an extremely interesting discussion on variations in intellectual performance due to variations in the proportion between ﬁre and water in 78 Other, more peripheral evidence (dealing less explicitly with intellectual capacities) is discussed in ch. Aristotle on the matter of mind 231 the body;80 and there may be other medical inﬂuences as well,81 especially of dietetics, for it was certainly one of the claims of dietetics in Aristotle’s time to provide a physiologically founded doctrine of ‘the good life’. Now it is certainly true that Aristotle’s psychology is much richer and much more sophisticated than that of the medical literature, but it should not be overlooked that there is also a ‘technical’ side to Aristotle’s psychology, an interest in the ‘mechanics’ of cognition and in modalities of thinking such as concentration, analytical powers, creativity, quickness (tacutv) of thinking and intuition (gc©noia, eÉstoc©a),83 habituation and repetition, and degrees in capacities to all these activities. It very rarely comes to the surface in On the Soul, but it ﬁgures more prominently in the Parva naturalia and in the zoological works, mostly when one species of animals is compared with another or when different members of one species are compared with one another, and mostly in contexts in which some sort of disturbance or aberration in cognitive behaviour is discussed. It is in these contexts that bodily factors are made responsible for these dis- turbances or aberrations; Aristotle does not explain what the normal bodily conditions for a normal functioning of thinking are, and they can only be deduced indirectly. However, it is very likely that the concept of ‘the mean’ plays an important part here. Here, too, there seems to be a tension between a ‘relativistic’, biological view of man as a zä on at the end of a scale which 80 For a discussion of these chapters see the commentary by Joly and Byl (1984). The doctrine of pneuma may be inspired by Diocles of Carystus (see Longrigg (1995) 441). On the claims of dietetics, and its relation to philosophy in the fourth century see also G. I should suggest that this difﬁculty is to be related to Aristotle’s endeav- ours to account for variations in psychic capacities and their performance by reference to variable bodily (anatomical, physiological, pathological) fac- tors – although it is not quite clear how these factors are to be accommodated within the ‘canonical’ doctrine of the incorporeality of the intellect and the changelessness of the soul. It is certainly to Aristotle’s credit as a scientist that he recognises the existence of these variations, most of which are prob- ably to be classiﬁed as belonging to the category of ‘the more and the less’ (diaforaª kaq’ Ëperocn). Moreover, when it comes to physical defects, he also seems to apply a sort of principle of natural compensation, which manifests itself in his belief that nature (i. Aristotle on the matter of mind 233 but whose existence, however marginal their importance may be, Aristotle recognises as interesting and in need of explanation89 – an explanation which invokes the principle that even within the category of ‘what is con- trary to nature’ (t¼ par fÅsin) there is such a thing as ‘according to nature’ (t¼ kat fÅsin). However much this may seem to be applauded, it remains unclear how these gradualist and compensatory explanations should be accommodated within the ‘normative’ theory of De an. To be sure, it may be asked whether there is actually such a tension, for it might be argued that all instances of bodily inﬂuence on intellectual activ- ity discussed above can be classiﬁed under the rubric of the ‘dependence of the intellect on appearances’. Whether this affects the thesis of the incorporeality of the intellect, remains to be seen. The only terminological point we can make is that a number of passages assign an important role to dianoia, and it may be that this is Aristotle’s favourite term for intellectual activity on the borderlines between sense-perception and thinking; one sometimes gets the impression that it refers to a particular kind of thinking, a sort of attention, in any case a directed and concentrated intellectual activity (or the capacity to this). Neuhauser, however, rejected Baumker’s view by pointing¨ ¨ to a number of passages in which the verb dianoeisthai seems to be used as a general, non-speciﬁc term for any intellectual activity, including that of nous. There is, indeed, abundant evidence that in the border area between sense-perception and thinking, where elu- sive faculties such as ‘incidental perception’ (the perception that that white thing over there is the son of Diares), ‘common sense’ and imagination are at work, Aristotle is not always clear whether we are dealing with operations of the sensitive or the intellectual part of the soul. The question whether the judgement of images is a sensitive or an intellectual activity presents itself very strongly in On Dreams, where sometimes one sense (sight) corrects the other (touch), as in 460 b 21–2, but sometimes also an intellectual faculty is at work (as in 460 b 18–19), and sometimes it is unclear which faculty is judging (461 b 3ff. Aristotle on the matter of mind 235 Let us ﬁnally turn to the question of the kind of connection or corre- spondence between the bodily conditions referred to and the intellectual activities they are said to accompany or inﬂuence. Of course, Aristotle has appropriate language at his disposal: on a structural level (where bodily inﬂuences are related to constitution types such as the melancholic nature, to deformations such as dwarfs, or to natural conditions such as hardness of the ﬂesh) he may say (as he often does in Parts of Animals and Genera- tion of Animals) that form does not completely ‘master’ (krate±n) matter, which results in deformed (pephrwmna) or ‘imperfect’ (tel¦) struc- tural capacities, or that material natural factors ‘impede’ (mpod©zein) the full realisation of the formal nature. Thus apart from saying that bodily changes ‘correspond with’ or ‘accompany’ psychic activities, which does not com- mit itself to a speciﬁc type of causal relationship,99 we may go further and say that bodily states and processes act on psychic powers or ac- tivities just as well as psychic powers may be said to ‘inform’ bodily structures. Tobe sure, in the Physiognomonica intellectual capacities are rarely referred to,101 and the author mainly deals with moral dispositions and characteristics. He refers to stock examples such as drunkenness and illness, and he also uses love, fear, pleasure and pain as examples of how emotional states may inﬂuence the condition of the body, thus indicating that there is a reciprocal relationship between body and soul. In particular, it should be asked to what extent these passages present a challenge to the doctrine of the 100 Phgn.
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