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The electronic energy bands and wave functions of cubic $3C$-SiC have been calculated in the first-principles Hartree-Fock-Slater model, making use of the discrete variational method. A comparison is made between experimental optical data, calculated indirect transitions, and theoretical results for ${\ensuremath{\epsilon}}_{2}(E)$ and reflectivity. The valence-band density of states is found to be in reasonably good agreement with x-ray emission spectra.

The x-ray $K$-emission spectrum and the soft-x-ray absorption spectrum are calculated for diamond and compared with experiment. The influence of transition matrix elements, calculated in a one-electron approximation, is discussed. Binding-energy corrections on the core and valence states are estimated and used to explain observed shifts between band transition energies and experimental data. Approximate methods are used to study localized valence relaxation effects on the transition matrix elements in emission.

SummaryIn 1971 the British Museum bought a fourth-century silver spoon with Christian symbols. An undated document acquired with the spoon showed that it was the survivor of a hoard from Biddulph, Staffordshire. In 1973 notes made in January 1886, about the discovery of the spoon, were found in a notebook compiled by A. W. Franks. The newly acquired spoon proves to have been one of a hoard of four spoons found at Whitemore Farm, Biddulph. The find-place of the spoon suggests a possible direct link between Chester and Buxton, while its dating adds to the sparse testimony for late-Roman life in the north-west of the province. The style of the lettering may indicate that the spoon was made in the East Mediterranean, and the Christian symbolism adds to the stock of evidence about the cult in the western Roman Empire.

Calculations of the electronic states of clusters of atoms have been carried out in recent years for the purpose of representing the states of ordered or disordered solids. We propose a boundary condition to be put on the cluster that should simulate the effect of the system outside the cluster better than the ones presently in use. During the past few years a number of uses for multiple-scattering-cluster calculations have been found for studying electronic states in condensed matter. For example, Johnson [l] and Keller [2] described such calculations at a conference at Menton in September of 1971. We will write out the general equation for the oneelectron Green's function in the neighborhood of a cluster and use this as a basis for a new boundary condition that we propose for use when the cluster is part of a solid. The first step in a cluster calculation is to generate a local one-electron potential function for a given array of atoms. This potential is then approximated by writing it as a sum of non-overlapping spherically symmetric potentials within spheres centered on each atom with the potential in the region between the spheres being a constant. This muffin-tin potential facilitates the use of multiple-scattering theory [3, 41 on the problem because the t-matrices that enter are diagonal in the angular momentum representation. Boundary conditions can be applied to the cluster using a diagonal t-matrix if the cluster is circumscribed by a sphere and the potential in the region outside the sphere is symmetric about the center of the cluster. Taking the origin of the coordinate system to be the center of the cluster, the potential for the system described above may be written as v(r) = vc(r) + v~( r ) (1) where Vc(d = x %(I r Rn I) (2)

There is much evidence from the history and from the geographic distribution of diverticular disease that it is the result of a deficiency of fiber, and in particular cereal fiber, in our modern over-refined diet. The symptoms of the uncomplicated form of the disease can be abolished or relieved by adding bran to the diets of the majority of patients. The low-residue diet formerly used to treat the disease is contraindicated, as it is the cause of the condition.

Summary Diverticular disease of the colon causes symptoms even in the absence of inflammatory diverticulitis. These symptoms vary from vague dyspepsia to severe colic which may lead to resection of the sigmoid for ‘diverticulitis’. This paper discusses the use of a high fibre diet, including miller’s bran, in the treatment of uncomplicated diverticulosis. In the majority of cases this diet relieves symptoms and lessens the need for surgery in diverticular disease.

The present article is the second of a series of three papers dealing with the morphology of the chromosomes of Drosophila melanogaster as these appear in the salivary glands of larvae, and to the presentation of a new type of chromosome map. As in my paper on the X chromosome, which appeared recently in this journal, the brief descriptions and the numerous figures have been presented primarily with the view of assisting other investigators in the ready identification of the various landmarks along the two arms of the third chromosome, because it is clear that study of salivary gland material is going to play an important part in the future genetic studies on Drosophila. The cytological map we are able to present now is little more than a skeleton, in spite of the fact that some 33 translocations have been analyzed. The reason for this is two-fold. In the first place, a great many of the breaks are bunched between rather narrow genetic limits. Thus out of a total of 36, 17 fall between the genetic limits of scarlet and pink. In the second place, the markers used in the original experiment were rather widely scattered and neither the time nor, in some instances, have the necessary stocks been immediately available for the finer analyses needed to determine more exactly the genetic limits of these breaks. Miss META SUCHE is making these determinations and by the time this article goes to the printer we should be able to add new data.' I n the meantime, the morphological positions of the breaks will be indicated. No doubt many other investigators have breaks in the third chromosome, the genetic limits of which have been relatively exactly determined, and it is believed that they will have no difficulty in placing these cytologically with the aid of the topographical maps presented in this study. In this way within a few years we should have a large number of gene loci placed within narrow morphological limits. Aside from the usefulness of the topographical maps for the study of all types of chromosome rearrangements and the problems associated with this branch of cytogenetics, perhaps the points of greatest general interest center around the question of chromosome structure. For the present study shows very clearly that the third chromosome is differentiated

1. Origin of the idea of progress. It arose in Greek thought from the changes and processes in nature and life. But the notion of regress was opposed to it These conflicting views result from the different types of minds. 2. Brief historical survey. The views of progress and regress are traced in Greek and Roman thought, throught early Christianity and the Middle Ages, the Renaissance and the eighteenth century. The theory of evolution in the nineteenth century made progress a necessary law of nature and gave the doctrine its first conscious scientific form. But criticism shows that it fails like its predecessors. 3. Possibilities and limitations of progress. Only in Psychical nature of man has there been real progress. Intellectual, aesthetic, and ethical progress have been unquestionable. Every science and art have been advanced. 4. The actual progress of human intelligence. This is seen in the improved art of living mechanical inventions, and division of labor. But industrial evolution has brought with...

lneed carcinogenesis than the adult thyroid. 7 Campbell. J. E., G. K. Murphy, A. S. Goldin, H. B. Robinson, C. P. Straub, F. J. Weber and H. Lewis, Am. J. Public Health, 49, 225 (1959). 8 "Strontium Program-Quarterly Summary Report,'' Health and Safety Laboratory Document [SL-55, U.S. Atomic Energy Commission, New York Operations Office (1959). 9 The evaluation of the constant in this equation is based on physical and biological data for ine-131, which have been summarized, for example, in "Recommendations of the International mmission on Radiological Protection," Brit. J. Radiol., Supplement No. 6 (1952). It is assumed It the effective half-life of iodine-131 is 7.7 days and that the effective beta energy is 0.19 Mev. 0 A recent survey of 312 children under the age of six in suburban Long Island by H. H. Neumann, -h. Pediat., 74, 456( 1957), gave a mean value of 840 ml of fluid cow's milk consumed per day h the lower third of the group averaging 647 cc per day and the upper third averaging 1,005 cc day. 1 Since evaporated milk will tend to be several months old before it is consumed, its iodine-131 ivity should be virtually nil. 2 Boyd, E., in Handbook of Biological Data, ed. by W. S. Specter (Philadelphia: W. B. Saunders ., 1956). a Dunning, G. M., Nucleonics, 14, No. 2, 38 (1956). 4 See, for example, R. L. Gunther and H. B. Jones, U.S. Atomic Energy Commission Document 'RL-2689 and addendum (1954). 5 Oddie, T. H., Brit. J. Radiol., 24, 333 (1951). 6 Middlesworth, L. Van, Nucleonics, 12, No. 9, 56 (1954) and Science, 123, 982 (1956); Comar, L., B. F. Trum, U. S. G. Kuhn III, R. H. Wasserman, M. M. Nold, and J. C. Schooley, Science, , 16 (1957). 7 Spiers, F. W., Brit. J. Radiol., 29, 409 (1956). s It should be noted that with the cessation of nuclear weapons testing in November, 1958, nan thyroid levels of radioiodine should decline exponentially and by January, 1959, there ,uld no longer have been any appreciable contamination of milk with radioiodine from past ipons tests. The level of radioiodine in cow's milk may well be the most important index of rt-term environmental contamination with fission products whether from weapons tests or er sources [see discussion in Safety Aspects of Nuclear Reactors, ed. C. R. McCullough (New rk: D. Van Nostrand Co., 1957), 28].

Certain diseases are absent or rare in countries that have been little affected by industrialisation. Here diets containing the natural amount of fibre are eaten and result in large, soft stools that traverse the intestine rapidly. By contrast, the refined low-fibre foods of the economically developed countries produce small firm stools which pass through the gut slowly. This paper records over a 1000 transit-times of various ethnic groups at home and abroad, together with the weight of stool passed daily. It is suggested that dietary fibre has a role in the prevention of certain large-bowel and other diseases which have become prevalent in Western countries.

The electronic band structure of graphite has been calculated from an ab initio variational approach using a linear-combination of atomic-orbitals (LCAO) basis of Bloch states, including nonspherical terms in the one-electron crystal potential. Matrix elements of the Hamiltonian are evaluated directly without any tight-binding approximations. The optical transitions deduced from the energy bands calculated using a single-layer crystal model agree nicely with recent polarized-light reflectance measurements. Details of the band structure are calculated for the three-dimensional Brillouin zone and related to the results obtained using the single-layer crystal structure. The results are encouraging, not only from the standpoint that the method employed is an ab initio approach with no special a priori assumptions, but also because the band structure is quite insensitive to the particulars of the crystal potential function.

SummaryA late-Roman silver ingot from Kent has recently come to light. It weighs one Roman pound and is stamped EX OFF CVRMISSI. All such ingots seem likely to have been distributed as imperial donatives to troops in the fourth century. They are related to presentation silver plate and other gifts of this type, and more than forty silver ingots are now known from the European Roman provinces. The only other known stamp by Curmissus—or perhaps the curator missionum—is on a broken ingot in the hoard from Coleraine, Co. Londonderry.

(1965). A Roman Silver Treasure from Canterbury. Journal of the British Archaeological Association: Vol. 28, No. 1, pp. 1-15.

A systematic method is presented for evaluating the electrostatic potential of point charge systems with inversion symmetry. By considering two simple ‘dumbbell’ structures, concise general potential expressions are deduced for point charge symmetries of the point groups containing the inversion operation. The explicit formulae presented for the most common basic symmetries are used as a basis to write down the potential for more complicated geometries formed by the combination of any number of basic symmetries. The equations are also valid for geometries obtained by certain distortions of the basic symmetry. The method presented here gives the potential at any general space point. The use of expressions in terms of the real spherical harmonics facilitates matrix element calculations, and with the potentials in such a form, symmetry arguments can be directly applied to eliminate many terms which vanish.

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THE race problem has been long an aggravating one in the United States, and tends to become even more pronouncedly so. Ever since slavery was instituted among us its evil consequences have acted upon both the black and white races with ever deepening complications. We have abolished slavery as an institution and survived a civil war in so doing, but 6he perils of race hatred and antipathy remain with us and local race warfare threatens us now and again. In many parts of the South in particular, where the negroes are most numerous, the situation occasionally becomes one of grave social and political concern. Although it is impossible ever to make with certainty any prophecy concerning the future in relation to human affairs, it is nevertheless always interesting to observe those great natural laws operative among men, calculate the goal towards which they move

1. A cytoplasmic basophily, which is removed when cells are treated with a ribonuclease enzyme, has been used as a means of identifying ribose nucleic acids and of following their distribution in the cells of the anthers of Rhoeo, and to a lesser extent in the pistil of the flower. Rapid cell growth is invariably accompanied by large amounts of ribonucleic acid in the cytoplasm and heavy deposits of chromatin in nuclei. 2. In young anthers the cytoplasm of both tapetal and sporogenous tissues is extremely rich in ribonucleic acid. As the pollen mother cells prepare for the meiotic divisions, the ribonucleic acid disappears from the cytoplasm, presumably being passed into the nucleus and changed into desoxyribose nucleic acid (chromatin). Initially the cytoplasm of microspores is devoid of basophilic material, but as they grow into mature pollen grains large amounts of ribonucleic acids accumulate in the cytoplasm. 3. The growth of tapetal cells is accompanied by one or more endomitotic nuclear division cy...

PRIMARY hypogammaglobulinemia or agammaglobulinemia has received considerable attention since the original description by Bruton1 in 1952. Good2 3 4 5 has written extensively on this subject and has defined the condition as a metabolic disorder featured by an enhanced susceptibility to bacterial infection, absence of gamma globulin from the serum, absence of antibodies from blood and tissues and failure of immunologic response to antigenic stimulation. There are two types: the congenital,6 which is a sex-linked mendelian recessive disorder, occurs in males and is manifested early in childhood; and the adult or acquired primary type, which is diagnosed in adult life, occurs in both . . .

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The British Museum acquired in November 1961 a Roman marble portrait head (pl. XLVI) found at Broadbridge, three miles west of Chichester (fig. 1). It was given to the museum by the late Captain A. W. F. Fuller through the National Art-Collections Fund.

Seventy patients with diverticular disease of the colon were treated with a high-residue, low-sugar diet including unprocessed bran. Follow-up for an average of 22 months showed marked relief of symptoms in 62 patients. Bowel habit was restored towards normal and abdominal discomfort relieved. Only seven patients were unable to give up the use of laxatives. Eight patients did not tolerate the bran diet, and one of these needed surgical treatment. None of the 62 patients who took the diet needed surgery.

The recently developed discrete-variational method (DVM) for the energy-band problem has been combined with the Korringa---Kohn---Rostoker (KKR) procedure to adapt the latter to treat general one-electron crystal potentials. Orbitals obtained from a KKR calculation for the muffin-tin average of the full Bloch Hamiltonian are used as trial variational functions for treating the complete problem within the framework of the DVM. Non-muffin-tin corrections originating from all regions of the unit cell are explicitly included by diagonalization of the relevant secular matrix in this basis set. This combination of the DVM and KKR methods to a large extent achieves the main advantages of each scheme and promises to comprise an efficient procedure for calculating the electronic structure of crystal compounds. With this method there is no limitation to a single-type basis set; for some purposes, it may be useful to supplement the KKR orbitals with other trial functions. The high accuracy that is achieved allows definitive conclusions to be drawn concerning the effects of the non-muffin-tin corrections on electronic structure. Illustrative results given for an application of the method to paramagnetic nickel demonstrate this point. An extension of the method is described by which the non-muffin-tin potential and charge-density corrections can be included in the multiple-scattering approach to the electronic structure of molecules.

A general variational method for efficiently calculating energy bands and charge densities in solids is presented; the method can be viewed as a weighted local-energy procedure or alternately as a numerical integration scheme. This rapidly convergent procedure circumvents many of the difficulties associated with the evaluation of matrix elements of the Hamiltonian in an arbitrary basis and treats the general nonspherical potential with no more complication than the usual "muffin-tin" approximation. Thus the band structure of ionic and covalent materials can be calculated with realistic crystal potentials. As an example, the method is applied to the one-electron model Hamiltonian with a nonspherical local potential, using a linear combination of atomic orbitals basis. Matrix elements of the Hamiltonian are evaluated directly without decomposition into atomic basis integrals; no "tight-binding" approximations are made. Detailed calculations are presented for the band structure and charge density of bcc lithium which demonstrate the feasibility of our method, and reveal the sensitivity of the energy bands to nonspherical and exchange components of the crystal potential. Various prescriptions for the construction of crystal potentials are considered, and convenient least-squares expansions are described. The extension of these methods to nonlocal potentials such as are encountered in the Hartree-Fock self-consistent-field procedure is discussed.