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This note considers systems subject to stochastic initial runtime cost immediately after a renewal and a deterministically increasing operating cost rate thereafter. The problem of establishing the cost-optimal renewal rule is generally set up as a readjustment problem. Using renewal-theoretic results, the note formulates and solves the general readjustment problem for self-contained systems. In the case of a linear cost rate, it gives the complete solution.

A modulated structure can be depicted as a section through a four-dimensional periodic structure. In the latter, each atom is represented by a string continuing endlessly in the overall direction (e4) of the normal to R3, R3 being the hyperplane of the section. The strings have periodic bends or densifications for displacive and substitutional modulation respectively. Formulae for structure factors can be derived from this picture with little effort. The pseudo-symmetry of modulated structures can be described conveniently in this picture. Each four-dimensional space group to which the four-dimensional structure can belong is a possible MS3 (modulated three-dimensional structure) group of pseudo-symmetry, and is called an MS3 space group. It is shown that MS3 point groups are reducible in the form Q⊕∊. 1, where 1 is the unit 2 × 2 matrix, and ∊ = ± 1. A list is presented of these 31 groups written as black-and-white or colourless groups of three-dimensional symmetry. The MS3 space groups are discussed briefly. As an example of the peculiar differentiations caused by e4 being a unique direction, the 23 MS2 space groups are listed explicitly. Finally, it is shown that MS groups are essential for the description of MS symmetry, because very often the latter cannot be represented completely and unambiguously by the normal space group of an approximate superstructure.

The relative rms deviation σ of the intensity of a rapidly rotating polycrystallite specimen is σ=[6.5R sinθ]/[h(mNeff)½], where R=goniometer radius, θ=Bragg angle, h=(hf+hs)/2, hf=length of focal spot, hs=length of receiving slit, m=multiplicity factor, and Neff the effective number of irradiated crystallites. Experimental data on silicon powder specimens are presented to show the dependence of σ on crystallite sizes, choice of x‐ray wavelengths and various other experimental parameters. Comparisons of data for rapidly rotating and stationary specimens having crystallite sizes in the 30–50 μ range show that rotation improves σ by a factor of 7 or 8 for peak intensities and 4 or 5 for integrated intensities, using a standard diffractometer.

The logarithmic spiral form of Barrau d’s monochromator can be obtained to a good approximation by exerting unequal bending moments on the short edges of a rectangular crystal plate. In the first two paragraphs some aberration formulas are derived pertaining to the asymetrical Barraud -type monochromator. In § 4 the new way of mounting is described. The aberration due to its approximative character is calculated. It appears to be negligible in the case of a monochromator, constructed and successfully used in this laboratory, the details of which are described in § 6. Finally it is an advantage of the device that there is no high precision work needed in making the crystal holder; further, that the monochromator can easily be set to a large range of wave lengths and crystal-to-focus distances.

For the purpose of accurate intensity measurements the use of transmission specimens is recommended. Apart from special advantages with respect to certain features e.g. surface roughness, they allow the measurement of the orientation distribution over a large range, using off-symmetry azimuth values. Correction for preferred orientation should then be possible, provided a simple texture model – a cylindrico-symmetrical needle-type texture – can be assumed. Some computing schemes for carrying out the elimination of the texture parameters are discussed.

The paper deals with the question whether the phases intermediate betweenγ- andβ-MnO2, which occur upon heating the former, possess the same type of random layer structure which has been proposed and confirmed earlier forγ-MnO2. In order to test that hypothesis, the powder diffraction pattern has been computed for five different values of the pyrolusite concentrationp in the random structure. The ensueing curves account for the main features of the intensity records of samples heated at different temperatures. The remaining discrepancies are definitely reduced if each record is compared with an appropriate weighted average of theoretical curves, indicating that in each sample the values ofp are distributed within a wide range.

Despite the advances of the electron mtcrodiflraction technique, the determination of unit cells of microcrystalline compounds still depends in many cases on the interpretation of the X-ray powder pattern. The feasibility of this interpretation depends strongly un the precision of the data, the present-day level of which is far from its physical limit. It could be improved by application of monochromators in diflractometry. Some possible methods are discussed. With regard to interpretation, a survey of existing methods is given (Lipson, Ito, de Wolff, Szoldos). Some of these techniques are suitable for computers, at least in the initial phase of the procedure. This is illustrated by application of a zone-finding program for the complete solution of a given pattern. Finally, the influence of impurities and other disturbing factors is discussed.

Expressions are derived for the relative r.m.s. errorσ of diffractometer intensity measurements. The result for stationary specimens: $$\sigma = 4R[\sin \theta /m w h N_{eff} ]^{\tfrac{1}{2}} $$ withh=1/2(h F+h S) and $$N_{eff} = cA\bar v/\mu v^2 $$ , is identical with the result of Alexander c.s.1), except for a slight difference in the numerical constant and in the definition ofw. The value of this parameter is found to lie betweenɛR+(w F, wS) min (the last term indicating the smallest of the widthsw F andw S) andɛR+1/2(w F+w F); it reaches the latter limit in the case of integrated intensities being measured by totalizing counts while scanning through a line. For rotating specimens the particle statistics error turns out to be almost independent ofw. The following approximative formula is established:σ=6.5R sinΘ/h(mN eff)1/2, showing that the factor of improvement resulting from specimen rotation is of the order of (h/w)1/2.

Es wird eine Methode beschrieben, die eine Registrierung der Schlaftiefe, der Bewegungen aller Gliedmasen, der EKG-Kurve, der Atmung, der Augenbewegungen und des galvanischen Hautreflexes wahrend der ganzen Dauer des Schlafes ermoglicht. An Hand von uber 180 bisher aufgenommenen Schlafkurven bei Gesunden und bei psychisch Kranken lassen sich gewisse Unterschiede des Schlafverlaufes bei den verschiedenen Krankheiten erkennen. Es besteht die Hoffnung, das die Schlafkurven zu differentialdiagnostischen Erwagungen mit herangezogen werden konnen, z. B. zur Abgrenzung endogener gegenuber reaktiven Depressionszustanden. Auch zur Aufklarung der Ursachen unklarer Schlafstorungen bei anderen Erkrankungen scheint die Methode geeignet. Fur die Begutachtung Hirnverletzter ist es wichtig, das sich die Moglichkeit ergibt, geklagte Schlafstorungen zu objektivieren. Es ist vorgesehen, die rund 300000–400000 Daten aus insgesamt 200 Kurven mittels einer elektronischen Rechenmaschine auszuwerten, um weitere Aufschlusse uber die Schlafstorungen zu erhalten.

The orthorhombic compound β-Mg2(OH)3Cl is isotypic with atacamite, Cu2(OH)3Cl The precise determination of its atomic parameters is described as an example of the possibilities offered by modern high-resolution powder diffraction methods. The results prove that from the irregular (4 + 2) coordination of the cations in atacamite, at most a trace is left in the Mgcompound.

The novel type of Guinier camera described in this paper is characterized by a combination of several cameras in a compact unit using a single focusing monochromator and a single film, and by the disposition of the camera relative to the monochromator in such a manner that α-doublet diffraction lines coincide for a θ value of, say, 15°. In this way an exceptionally high resolving power is obtained in a considerable range of glancing angles, centred about this value, which contains the most selective lines for analytical purposes. The line width in the respective cameras is discussed, and the conclusion is reached that in the significant region θ < 30° there is no appreciable difference between the outer and the middle cameras of the unit. With a view to comparison purposes, the line shift for the outer cameras is also calculated; it appears to be of little consequence. Finally, short descriptions of a twofold and of a fourfold camera are given.

The author studies the behaviour in vitro of organ fragments of Loligo vulgaris embryos at hatching stage. These fragments are maintained in three different media. The time of survival of cells is 20 to 25 days in the medium I(sea water), 40 days in the medium II(perivitellin fluid) and 70 to 80 days in the medium II(perivetellin fluid + horse serum). It is this medium III that the original explant is transformed into a typical primary cell culture.

Surface modifications appear prior to the joining stage of the palatal shelves. They take the same appearance in vivo and in vitro: cell agglutination, nuclear hypertrophy, exfoliation and release of cellular material, formation of uniting bridges across the gap between the shelves.

Using indirect immunofluorescence procedure with an anti-synthetic LHRF serum, pericarya of neurons producing LHRF or an LHRF-like substance were revealed in hypophysectomized Bufo vulgaris. They are localized principally in the forebrain near the posterior end of the first and second ventricles. The fluorescent axons coming from these pericarya are visible on their pathway to a region near tha pars tuberalis and to the median eminence.

Ehe man zum Entwurf der Organisation eines Unternehmens schreitet, sollte man das allgemeine Ziel, das es erreichen soll, genau erwagen und die verschiedenen Mittel und Wege erortern, die die grosstmogliche Sicherheit bieten, es wirklich zu erreichen. Nur so kann es klar werden, in welche Form die Organisation selbst, so zu sagen, „gegossen“ werden muss, um vollbefriedigend zu wirken.

Por primera vez se han analizado las relaciones estructura-funcion de diez derivados del 9α-cortisol substituido usando tecnicas de regresion de parametros multiples. Se concluye que los factores electronicos y estericos son de mayor importancia al determinar el efecto del substituyente, y que la union hidrofobica tambien es de importante consideracion. Se discute el significado de estos resultados.