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Showing papers by "Northwestern University published in 1970"


Journal ArticleDOI
TL;DR: A computer adaptable method for finding similarities in the amino acid sequences of two proteins has been developed and it is possible to determine whether significant homology exists between the proteins to trace their possible evolutionary development.

11,844 citations


Journal ArticleDOI
04 Dec 1970-Science
TL;DR: On the basis of analytical chemical data for numerous rain, river, lake, and ocean samples, the three major mechanisms controlling world surface water chemistry can be defined as atmospheric precipitation, rock dominance, and the evaporation-crystallization process.
Abstract: On the basis of analytical chemical data for numerous rain, river, lake, and ocean samples, the three major mechanisms controlling world surface water chemistry can be defined as atmospheric precipitation, rock dominance, and the evaporation-crystallization process.

2,885 citations


Journal ArticleDOI
TL;DR: In this paper, a 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.
Abstract: 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.

614 citations


Journal ArticleDOI
TL;DR: Trust and suspicion appear to underlie many social interactions Thus it is not surprising that they occupy an important role in various efforts to account for the stability or instability of a wide variety of human relationships as discussed by the authors.
Abstract: Trust and suspicion appear to underlie many social interactions Thus it is not surprising that they occupy an important role in various efforts to account for the stability or instability of a wide variety of human relationships One of the earliest systematic formulations of these concepts appeared in this journal over a decade ago (cf Deutsch, 1958) Yet little progress has been made since then toward a more satisfactory conceptualization of trust and suspicion This paper is devoted to the examination of both the theoretical and the methodological considerations relevant to the empirical study of trust and suspicion

523 citations


Journal ArticleDOI
TL;DR: In this article, 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.
Abstract: 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.

358 citations



Journal ArticleDOI
TL;DR: In this article, the authors examined the capillary instability of vertical liquid jets of different viscosities by imposing audio-frequency disturbances and found that non-linear effects dominate the growth processes.
Abstract: The capillary instability of vertical liquid jets of different viscosities have been examined by imposing audio-frequency disturbances. Real time sequences of photographs allow a direct measurement of growth rates of disturbances of various wavelengths. Results show that in general non-linear effects dominate the growth processes. This is in agreement with Yuen's analysis. The growth rate of the difference between the neck and the swell, however, agrees well with the linearized analysis of Rayleigh and Chandrasekhar. The non-linear effect causes a liquid jet to disintegrate into drops with ligaments in between. The sizes of the ligaments decrease with increasing wave-number. The subsequent roll up of the ligament into droplet, the eventual coalescing of the droplet with the main drop and drop oscillation have also been studied.

261 citations


Journal ArticleDOI
TL;DR: In this paper, a grand matrix equation describing mass transfer in geochemical processes is presented, and computer evaluation of this equation affords quantitative prediction of the extent to which minerals are produced and/or destroyed as well as changes in the composition of phases and distribution of species.

250 citations


Journal ArticleDOI
TL;DR: In this paper, the selfconsistent treatment of correlations in the electron liquid recently given by Singwi et al. is applied to calculations of the lattice dynamics of alkali metals.
Abstract: The self-consistent treatment of correlations in the electron liquid recently given by Singwi et al. is applied to calculations of the lattice dynamics of alkali metals. With the Ashcroft form for the pseudopotential, in which the only parameter is the core radius, good agreement with the measured dispersion curves is obtained for the four metals for which such data exist. For Na and K the fitted values of this parameter are close to those derived from Fermi-surface and liquid-resistivity data; for Li and Rb the fitted values lie between those obtained from the other physical properties. Phonon lifetimes due to the electron-phonon interaction are calculated for K. Finally, the cohesive energy, lattice parameter, and compressibility are derived; agreement with the measured values of all three quantities is obtained with a not unreasonable adjustment of the Hartree energy. The relation between the compressibility sum rule and the long-wavelength limit of terms containing third and fourth powers of the electron-phonon matrix element is evaluated for the case of Na within the same framework.

216 citations



Journal ArticleDOI
TL;DR: In this paper, the authors studied the propagation of heat pulses in NaF to higher temperatures in a purer crystal than studied by McNelly et al. At the highest temperatures the second-sound velocity fails to level off at the theoretically predicted limiting value.
Abstract: Propagation of heat pulses in NaF has been studied to higher temperatures in a purer crystal than studied by McNelly et al. At the highest temperatures the second-sound velocity fails to level off at the theoretically predicted limiting value.

Journal ArticleDOI
TL;DR: It is proposed that the tetralogy of Fallot basically is a “monology”, just 1 anomaly, namely, underdevelopment of the subpulmonary infundibulum and its sequelae, which facilitates angiocardiographic diagnosis of “masked” tetralogical in which the presence of this anomaly may be obscured by associated malformations.
Abstract: It is proposed that the tetralogy of Fallot basically is a “monology”, just 1 anomaly, namely, underdevelopment of the subpulmonary infundibulum and its sequelae. The parietal band (crista supraventricularis) and the adjacent infundibular free wall together form an abnormally small cone (conus) of muscle beneath the pulmonary artery, whereas the septal band is normally formed. The hypothesis that the essence of tetralogy is an abnormally small subpulmonary conus is illustrated by angiocardiographic and anatomic findings in typical tetralogy compared with the normal. This unifying concept, which needs experimental embryologic assessment, facilitates angiocardiographic diagnosis of “masked” tetralogy in which the presence of this anomaly may be obscured by associated malformations. To demonstrate this, a rare case is presented, the fourth known patient with coexisting tetralogy and cor triatriatum. This 20 year old man also had a patent ductus arteriosus and a right pulmonary sequestration. The resulting systemic level of pulmonary hypertension “masked” the coexistence of tetralogy, which angiocardiography made evident. Despite the absence of a pulmonary outflow tract gradient due to the association of severe pulmonary hypertension, autopsy confirmed that this patient displayed the angiocardiographic hallmark of tetralogy: an abnormally small subpulmonary infundibulum.


Journal ArticleDOI
TL;DR: The embryology, macroscopic structure, microscopic structure,fine structure, fine structure, function and pathology of the choroid plexus were reviewed.

Journal ArticleDOI
TL;DR: It is shown that splenic lymphocytes from mice immunized with viable attenuated mycobacterial cells or ribonucleic acid prepared from these cells will bring about inhibition of multiplication of virulent tubercle bacilli within normal mouse peritoneal macrophages in tissue culture.
Abstract: We have shown that splenic lymphocytes from mice immunized with viable attenuated mycobacterial cells (H37Ra) or ribonucleic acid prepared from these cells will bring about inhibition of multiplication of virulent tubercle bacilli (H37Rv) within normal mouse peritoneal macrophages in tissue culture. Apparently these lymphocytes, when stimulated with viable virulent tubercle bacilli, elaborate a filterable substance(s) which is responsible for this intracellular growth inhibitory effect.

Journal ArticleDOI
TL;DR: In this paper, the spectral behavior of protons forming hydrogen bonds in a solid is investigated, and the ionic defect H3O+ in the ice crystal is used as a basic model.
Abstract: The spectral behavior of protons forming hydrogen bonds in a solid is investigated. The ionic defect H3O+ in the ice crystal is used as a basic model. Strong interaction with optical phonons (wagging vibrations) is considered to infinite order by construction of a quasiparticle analogous to the small polaron. We predict for the absorption profile a broad peak with some fine structure at the low‐frequency side. Temperature dependence, red shifting, and mass dependence of the spectrum are discussed.

Book ChapterDOI
TL;DR: The events that take place during meiosis of the Drosophila oocyte are discussed, including the end-to-end pairing with chromosomes of similar size and the paracentric heterochroinatin transcribes rcrRNA, which causes nearby recombinases to detach from the chromosomes.
Abstract: Publisher Summary This chapter discusses the events that take place during meiosis of the Drosophila oocyte. Prior to the meiotic prophase, the chromosomes attach to specific sites on the inner surface of the nuclear envelope. The chromosomes replicate their entire DNA except for the synaptomeres. During leptonema, histone-deficient synaptomeres pair, reducing the length of each chromosome by a factor of 500 times. The reaction serves to zip homologous chromosomes together, starting at the telomeres and ending at the centromeres. Eventually, a synaptonemal complex extends from one end of the bivalent to the other. The paracentric heterochroinatin transcribes rcrRNA, which causes nearby recombinases to detach from the chromosomes. Recombinases detach prematurely from chromosomes if the nonsister chromatids contain nonallelic DNA segments. During diplonema, the zygosomes detach and the bivalents open up. However, separation of the bivalents is prevented by chiasmata. Chromosomes lacking chiasmata undergo an end-to-end pairing with chromosomes of similar size. In each gametocyte, the centromeres of the chromatids making up each homolog become functional. The second meiotic division distributes each sister chromatid to a separate gametic nucleus.

Journal ArticleDOI
TL;DR: In this paper, the light intensity distribution in a perfectly mixed photoreactor has been studied experimentally and analytically, and it was found that this model, which seems appropriate and allows reasonable computations, is somewhat in error owing to the neglect of the finite size of the lamp and the existence of reflection and refraction effects within the reactor.
Abstract: The light intensity distribution in a perfectly mixed photoreactor has been studied experimentally and analytically. Experimental measurements of intensities within the reactor were made with a specially designed light probe. These data were then used to test the validity of a model which treats the ultraviolet lamp as a linear source radiating in all directions. It was found that this model, which seems appropriate and allows reasonable computations, is somewhat in error owing to the neglect of the finite size of the lamp and the existence of reflection and refraction effects within the reactor. An empirical correction function was determined for use with the model which then yields predictions in close agreement with experimental data when the reactor is filled with a light absorbing liquid.

Journal ArticleDOI
TL;DR: The combined use of chemical analyses and zone electrophoresis permitted the major AG polymers to be identified and measured in tissues without the use of ion-exchange columns.



Journal ArticleDOI
TL;DR: In this paper, five experiments are reported in which single-trial free recall followed various frequencies of repetition under massed (MP) and distributed (DP) schedules, and all experiments showed the DP schedule to result in far better recall than the MP schedule, and the difference between MP and DP increased as the frequency of repetition increased.

Journal ArticleDOI
TL;DR: In this article, a convex upper and lower bound on the nonconvex cost functions partially describes the optimal policy for the stochastic cash balance problem, where both fixed and proportional costs are incurred whenever the inventory is changed in either direction.
Abstract: The stochastic cash balance problem is an inventory problem in which the stochastic cash or inventory change can either be positive or nonpositive, and in which decisions to increase or decrease the inventory are permitted at the beginning of each time period. The paper studies problems in which both fixed and proportional costs can be incurred whenever the inventory is changed in either direction. An example is used to demonstrate that when these costs are positive and the loss function is convex, a simple policy analogous to a two-sided s, S policy is not generally optimal. The example is also used to display the relations between the cash balance problem and inventory problems previously studied by Scarf and Veinott. When proportional costs of changing the inventory are zero, the two fixed costs are equal, the loss function is symmetric quasi-convex, and the problem's probability densities are quasi-concave a simple policy is shown to be optimal. For the cases in which simple policies are not optimal, the paper develops a technique which employs convex upper and lower bounds on the nonconvex cost functions partially to describe the optimal policy. It is suggested that this convex bounding technique may provide an approach to studying the cost implications of following simple, nonoptimal policies in inventory problems for which the optimal policy is complex.


Journal ArticleDOI
TL;DR: In this paper, the authors examined the social effects of a legal reform on the highway death rate using the Interrupted Time-Series research design, a method of analysis that has broad potential use in studies of legal change more generally.
Abstract: The social effects of a legal reform are examined in this paper utilizing the Interrupted Time-Series research design, a method of analysis that has broad potential use in studies of legal change more generally. A previous demonstration of the applicability of this design to the sociology of law concerned the Connecticut crackdown on speeders (see Campbell and Ross, 1968; Glass, 1968). In that study, the substantive findings were that the crackdown had little effect on the highway death rate, and that it introduced certain unexpected and undesirable changes into the legal process in Connecticut. The present study concerns a similar attempt to lower the highway death rate through changes in the law, specifically the British Road Safety Act of 1967. Critical scrutiny of the data indicates that in this instance the legal change quite impressively achieved its goal. The British crackdown attempted to get drunken drivers off the road, and thus took aim at a scientifically demonstrated correlate of automobile accidents. The Connecticut crackdown, in contrast, was based on commonsense considerations unsupported even by correlational studies. Its sponsors claimed success prematurely, before such possibilities as random variation and statistical regression could be ruled out as explanations of an apparently strikii~g decline in accident rate. In the present study, similar claims turned out to be justified.


Journal ArticleDOI
TL;DR: In this paper, positive definite matrices have been studied in the context of Positive Definite Matrices (PDM) and positive definiteness matrices (PVDM).
Abstract: (1970). Positive Definite Matrices. The American Mathematical Monthly: Vol. 77, No. 3, pp. 259-264.

Journal ArticleDOI
TL;DR: In this paper, a model for intermediate-stage sintering relates the densification rate to the instantaneous geometry in the compact and to the volume and grain-boundary diffusion coefficients, despite concurrent surface diffusion, vapor transport, and/or grain and pore growth.
Abstract: A model proposed for intermediate-stage sintering relates the densification rate to the instantaneous geometry in the compact and to the volume and grain-boundary diffusion coefficients, despite concurrent surface diffusion, vapor transport, and/or grain and pore growth. Quantitative stereological methods can be used to measure the necessary geometric parameters. The suggested experiments would provide a detailed description of the evolution of the microstructure and calculated values for the grain-boundary and/or volume diffusion coefficients.

Journal ArticleDOI
01 Jan 1970
TL;DR: In this article, the constitutive equation for creep, shrinkage and thermal expansion of concrete and concrete is derived, which reflects correctly the effect of variable humidity and temperature, including the effects of size, shape and stress distribution.
Abstract: The constitutive equation for creep, shrinkage and thermal expansion, which reflects correctly the effect of variable humidity and temperature, including the effect of size, shape and stress distribution, is derived. Cement paste and concrete are treated as a multi-phase composite material, in which both the static and thermodynamic conditions of equilibrium must be considered.

Journal ArticleDOI
TL;DR: Comparisons made between Cayo Santiago and other primate groups under analogous situations reveal similar responses to food shortage.
Abstract: During early July 1968, a severe food shortage occurred on Cayo Santiago, an island colony of free-ranging rhesus monkeys (Macaca mulatta). The food shortage produced striking changes in the behavior of the monkeys. Within the one social group intensively studied, the total frequencies of grooming, play and fights decreased significantly; the frequency of matings also dropped; body contact, displacements by other groups, and non-displacement movements decreased, but not in statistically significant amounts. Changes in the percentage of total grooming attributable to related and unrelated monkeys reflected the stability of the rhesus matriline. Comparisons made between Cayo Santiago and other primate groups under analogous situations reveal similar responses to food shortage.