Showing papers by "University of Texas at Dallas published in 1976"
TL;DR: The results indicate that the fraction of ribosomes engaged in protein synthesis is about 0.8 at all three growth rates, which agrees with the previously observed ribosome efficiency at these growth rates.
Abstract: By evaluating the kinetics of radioactive labelling of nascent and finished polypeptides, the peptide-chain elongation rate for Escherichia coli B/r at three different growth rates (mu) was determined to be 17 amino acids/s for the fast-growing cells (mu equals 1.3 and 2.0 doublings/h) and 12 amino acids/s for slow-growing cells (mu equals 0.67 doublings/h). The results agree with the growth-rate-dependence of the rate of peptide-chain elongation found for the translation of newly induced beta-galactosidase messenger in this strain and under these conditions of growth [Dalbow & Young (1975) Biochem. J. 150, 13-20]. Together with the previously observed ribosome efficiency at these growth rates [Dennis & Bremer (1974) J. Mol. Biol. 84, 407-422] the results indicate that the fraction of ribosomes engaged in protein synthesis is about 0.8 at all three growth rates.
183 citations
TL;DR: Results from the aeroshell-mounted neutral mass spectrometer on Viking I indicate that the upper atmosphere of Mars is composed mainly of CO2 with trace quantities of N2, Ar, O, O2, and CO.
Abstract: Results from the aeroshell-mounted neutral mass spectrometer on Viking 1 indicate that the upper atmosphere of Mars is composed mainly of CO2 with trace quantities of N2, Ar, O, O2, and CO. The mixing ratios by volume relative to CO2 for N2, Ar, and O2 are about 0.06, 0.015, and 0.003, respectively, at an altitude near 135 kilometers. Molecular oxygen is a major component of the ionosphere according to results from the retarding potential analyzer. The atmosphere between 140 and 200 kilometers has an average temperature of about 180 plus or minus 20 deg K. Atmospheric pressure at the landing site for Viking 1 was 7.3 millibars at an air temperature of 241 deg K. The descent data are consistent with the view that CO2 should be the major constituent of the lower Martian atmosphere.
126 citations
TL;DR: A simple, one-step spectrofluorometric method, applicable in several buffer systems and in the presence of large concentrations of alkali metals, is applied to the determination of Tb3+-apoconcanavalin A association constants.
105 citations
TL;DR: For all complex space-times in which the self-dual part of the Weyl tensor is algebraically degenerate, Einstein's vacuum equations are reduced to a single differential equation of the second order and second degree as discussed by the authors.
Abstract: For all complex space-times in which the self-dual part of the Weyl tensor is algebraically degenerate, Einstein's vacuum equations are reduced to a single differential equation of the second order and second degree.
96 citations
Alcatel-Lucent1, University of Chicago2, Clemson University3, Rochester Institute of Technology4, Cleveland State University5, DuPont6, University of Illinois at Urbana–Champaign7, IBM8, Johns Hopkins University9, American Cyanamid10, Monsanto11, National Institute of Standards and Technology12, University of Texas at Dallas13, Oak Ridge National Laboratory14, Université Paris-Saclay15
TL;DR: In this article, TTF-TCNQ was measured along the $b$ axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TTE) to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories.
Abstract: New measurements of electrical conductivity along the $b$ axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) are combined with published results to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories The magnitudes of these measured conductivities do not necessitate the assumption of superconducting fluctuations or any other collective state in which the conductivity exceeds the limitations of single-particle scattering Since an adequate theory of the limitations of single-particle scattering for TTF-TCNQ does not exist at present, experiment alone does not rule out the possibility that collective effects may somewhat enhance or suppress the conductivity
93 citations
TL;DR: The general increase in MLP during the evolution of the primate species indicates that a corresponding general decrease in mutation rate may have occurred, and the high levels of MLP, MCC, EQ and N c represented in the living primates, as compared to other mammals, are considered to represent a major characteristic determining their evolutionary success.
80 citations
TL;DR: In this article, the integrated dosages, based on the erythemal sensitivity curve and on the Robertson-Berger sunburn meter sensitivity curve, have also been calculated, and these are found to vary with latitude and season in very nearly the same way as 307 and 314 nm radiation, respectively.
Abstract: Tabulated values are presented for ultraviolet radiation at the earth's surface as a function of wavelength, latitude, and season, for clear sky and seasonally and latitudinally averaged ozone amounts. These tabulations can be combined with any biological sensitivity function in order to obtain the seasonal and latitudinal variation of the corresponding effective doses. The integrated dosages, based on the erythemal sensitivity curve and on the Robertson-Berger sunburn-meter sensitivity curve, have also been calculated, and these are found to vary with latitude and season in very nearly the same way as 307 and 314 nm radiation, respectively.
80 citations
TL;DR: Gaussian populations and five algorithms are studied: linear discrimination with urlknown means and known covariance, lineardiscrimination with unknown means and unknown covariances, quadratic discrimination with unknown covariansces, and two nonparametric Bayes-type algorithms having density estimates using different, kernels (Gaussian and Cauchy).
Abstract: Given fixed numbers of labeled objects on which training data can be obtained, how many variables should be used for a particular discriminant algorithm? This, of course, cannot be answeredin general since it depends on the characteristics of the populations, the sample sizes, and the algorithm. Some insight is gained in this article by studying Gaussian populations and five algorithms: linear discrimination with urlknown means and known covariance, linear discrimination with unknown means and unknown covariances, quadratic discrimination with unknown covariances and two nonparametric Bayes-type algorithms having density estimates using different, kernels (Gaussian and Cauchy).
72 citations
TL;DR: It is concluded that the degree of hydration rather than the conformational state is the critical factor in determining which of the photoproducts will form in native DNA.
Abstract: — In an ethanolic solution native T7 DNA can undergo conformational transitions from the B conformation (0% ethanol) to the C-like (60% w/w ethanol) and the A (80% w/w ethanol) conformations. We have investigated the formation of three classes of thymine-derived photoproducts in T7 DNA irradiated (280 nm) in the B, C-like, and A conformations, which were monitored by circular dichroism measurements. We find that the predominant class of thymine-derived photoproducts in any conformational state is cyclobutyl dipyrimidines. While the ‘spore product,’ 5-thyminyl-5,6-dihydrothymine, which belongs to another class of photoproductsf does form in native DNA in the A conformation, its yield in denatured DNA at 80% ethanol is the same as that in native DNA. The yield of pyrimidine adduct, a third photoproduct class, is a maximum at 50–60% ethanol. This effect of ethanol is probably not due to the ethanol-induced C-like conformation, however, since pyrimidine adduct formation is not enhanced when T7 DNA is irradiated in the C conformation in 6 M CsCl or in intact phage. We conclude from these and other data in the literature that the degree of hydration rather than the conformational state is the critical factor in determining which of the photoproducts will form in native DNA.
61 citations
TL;DR: For non-conservative elements, the validity of themodel is improved if internal losses as well as outwashlosses are taken into account in the mass balance as mentioned in this paper, and equation (1) must be modified to account for thereactivity of the element in the lake.
59 citations
TL;DR: In this paper, the impact of structural interventions on group decision quality and group attitudes is examined, and the appropriateness of the techniques in various situations is discussed. But the authors focus on a direct comparison of consensual, nominal, and conventional decision making techniques in established and ad hoc groups.
Abstract: This paper focuses on a direct comparison of consensual, nominal, and conventional decision making techniques in established and ad hoc groups. The impact of the structural interventions on group decision quality and group attitudes is examined, and the appropriateness of the techniques in various situations is discussed.
TL;DR: The average number of rRNA genes per haploid genome (rRNA gene dosage) of the cells present in liver and brain was determined throughout the lifespan of the inbred C57BL/6J mouse strain and of human.
TL;DR: In this paper, the authors investigated the properties of neutral hydrogen at altitudes below 200 km where vertical diffusion strongly affects the hydrogen distribution and provided theoretical estimates and model calculations of large hydrogen flows upward from the region below 100 km.
Abstract: Thermospheric concentrations of neutral atomic hydrogen near and below the F peak are directly related to H+, O+, and atomic oxygen concentrations through the charge exchange equilibrium that is established between hydrogen and oxygen at these altitudes This chemical relationship, together with in situ measurements of ionospheric and neutral atmospheric concentrations by instrumentation on board the Atmosphere Explorer C satellite, is utilized to investigate properties of neutral hydrogen at altitudes below 200 km where vertical diffusion strongly affects the hydrogen distribution Data are discussed for a set of satellite orbits during quiet geomagnetic and solar conditions in February 1974; the resultant altitude variation of the derived hydrogen concentrations applies specifically to early afternoon at low latitudes between the winter solstice and the spring equinox A hydrogen concentration of (255 ± 05) × 105 atoms/cm³ is observed for these conditions at 300 km At lower altitudes the concentration profiles are interpreted in terms of vertical hydrogen flow The resultant daytime flux in the thermosphere is estimated to be (32 ± 10) × 108 atoms/cm² s The present observations thus support theoretical estimates and model calculations of large hydrogen flows upward from the region below 100 km They also support the concept of daytime thermospheric loss processes of greater magnitude than the traditional evaporative escape mechanism
TL;DR: It is suggested that tight supercoils are formed by induction of numerous kinks in the double helix between short, straight DNA segments, consistent with DNA kinks proposed by Crick & Klug (1975).
TL;DR: In this paper, the authors presented energy spectra and angular and spatial distributions of electron fluxes in the ionosphere resulting from precipitation of monoenergetic (E = 25, 50, and 100 eV) electrons.
TL;DR: The influence of gene conversion on allele frequencies is compared with that of spontaneous mutation and meiotic drive and the effects of conversion in a large random-mating population are derived.
Abstract: Gene conversion causes deviations from the 2:2 segregation of allele pairs in meiosis. Thus, gene conversion is a potential cause for changes of allele frequencies in populations. Equations are derived for the effects of conversion in a large random-mating population. The influence of gene conversion on allele frequencies is compared with that of spontaneous mutation and meiotic drive.
TL;DR: Near‐ultraviolet (near‐UV; 320–405 nm) irradiation of Escherichia coli B/r induces the formation in vivo of 4Srd‐Cyd adducts in transfer RNA, as evidenced by fluorescence spectrum changes of tRNA extracted from irradiated cells and reduced with NaBH4.
Abstract: — Near-ultraviolet (near-UV; 320–405 nm) irradiation of Escherichia coli B/r induces the formation in vivo of 4Srd-Cyd adducts in transfer RNA, as evidenced by (1) fluorescence spectrum changes of tRNA extracted from irradiated cells and reduced with NaBH4, (2) thin-layer chromatography on cellulose of hydrolysates of trichloroacetic acid-precipitable extracts of irradiated cells, and (3) comparison of these findings with adduct formation induced by near-UV irradiation of purified mixed tRNA from E. coli.
The kinetics of induction of the 4Srd-Cyd adduct in vivo, and the near-UV fluences required, provide strong support for our earlier hypothesis that formation of these adducts is responsible for near-UV-induced growth delay in E. coli.
01 Jan 1976
TL;DR: The concept of primary aging processes and the cross-linkage hypothesis of aging is reviewed and the major evidence indicating the natural accumulation of DNA adducts in the chromatin of mammalian species with increasing age is presented.
Abstract: There is now substantial evidence which points to the occurrence and biological importance of the formation of protein and other adducts to DNA after ultraviolet or ionizing radiation of cells (Smith, 1975a). Many of the reactive cross-linking agents formed on the irradiation of cells (e.g., free radicals and their derivatives) are thought to exist naturally within a cell but at a much lower concentration. In addition, there exist naturally within the cell many non-radical chemical agents such as the aldehydes which could also cross-link macromolecules (Harman, 1962; Bjorksten, 1962, 1974; Sinex, 1964). The possible parallel between radiation and naturally induced DNA adducts appears sufficiently great to warrant serious consideration of the natural occurrence of DNA adducts as an important primary aging process. The objective of this paper is to review the concept of primary aging processes and the cross-linkage hypothesis of aging and to present the major evidence indicating the natural accumulation of DNA adducts in the chromatin of mammalian species with increasing age.
TL;DR: A DNA extraction and purification procedure that is simple and reliable and gives a high percent DNA yield, which substantially reduces the selective loss of heterochromatin DNA sequences.
TL;DR: Photoreactivating enzyme from yeast shows increased activity if it is illuminated with near UV or short wavelength visible light prior to its use for photoenzymatic repair of UV-induced pyrimidine dimers in transforming DNA in vitro.
Abstract: Photoreactivating enzyme (PRE) from yeast (as semi-crude extract, or in highly purified form) shows increased activity if its is illuminated with near UV or short wavelength visible light prior to its use for photoenzymatic repair of UV-induced pyrimidine dimers in transforming DNA in vitro. This effect results from an alternation in PRE molecules changing those with low activity in the light-dependent step of the reaction to a higher activity. Light-induced activation of PRE preparations is slowly lost by dark storage for several hours to 1 day (faster at 23°C than at 5°C), but can be recovered repeatedly by renewed preillumination. The action spectrum for these preillumination effects generally resembles that for the photoenzymatic repair reaction itself, having its maximum in the same 355–385 nm region as the latter, but light of somewhat longer wavelengths (546 nm) is still effective. Preilluminated PRE is also more stable to thermal inactivation (65°C) than untreated enzyme.
TL;DR: A comprehensive survey of the proportion estimation methods so far found in the literature and a newly proposed method based on the concept of statistically equivalent blocks is presented in this paper, which is restricted to the case of normal mixtures only.
Abstract: The objective of this paper is to present a comprehensive survey of the proportion estimation methods so far found in the literature and a newly proposed method based on the concept of statistically equivalent blocks. All methods are restricted to the case of normal mixtures only. Graphical and semigraphical techniques are excluded. Several proportion estimation methods have been described and their properties discussed.
TL;DR: The results show that the mating-type gene mat2 not only has a function in copulation and meiosis, but that it also regulates the formation of the map1 gene product (map1 is a mating- type auxiliary gene).
Abstract: Mutants defective in various steps of the sexual cycle have been isolated from homothallic strains of Schizosaccharomyces pombe by Bresch, Muller and Egel (1968). These mutants include heterothallic h(+) and h(-) strains. We have isolated additional h(+) and h(- ) mutants from homothallic strains. Those mutants which are due to mutations in the mating-type region were analyzed in detail. Our results show that the mating-type gene mat2 not only has a function in copulation and meiosis, but that it also regulates the formation of the map1 gene product (map1 is a mating-type auxiliary gene). Some of the h( -) mutants have lost only one of the three functions while others are defective in at least two, and perhaps all three, functions. Further, we show that the mat1(-) allele of h(90) strains can mutate to mat1(+) but that mutations in mat2 appear to affect the mutational behavior of mat1. Finally, we describe a new inactive mating-type allele, mat2*, which is different from mat2(0) in that it can mutate to mat2(+).
TL;DR: This article developed a conceptual contingency framework which considers aspects of relationships among task, organization structure, and individual variables, and addressed issues of human fulfillment in the work setting, identifying expected interactions, incongruities, and outcomes among aspects of three sets of variables.
Abstract: This review develops a conceptual contingency framework which considers aspects of relationships among task, organization structure, and individual variables, and which addresses issues of human fulfillment in the work setting. It identifies expected interactions, incongruities, and outcomes among aspects of three sets of variables.
TL;DR: The Shivaji Sager Lake as discussed by the authors experienced a burst of seismic activity from September 1967 to January 1968 following the record water levels in the reservoir and included the earthquake of September 13, 1967 with magnitude 5.5 and the damaging December 10, 1967 earthquake of magnitude 6.0.
TL;DR: The results provide evidence of binaural interaction in normal-hearing subjects and indicate that FFR arises from at least two separate symmetric neural sources, possibly by iterative activation of brainstem evoked response (BER) generators.
TL;DR: Two-photon transitions have been observed from the ground state of atomic cesium to selected higher lying n2D levels up to n = 19 as mentioned in this paper, where the transitions were excited by a narrowband dye laser pumped by a nitrogen laser and detected by a space charge limited ceium vapor photodiode, and the fine structure intervals of the n 2D levels for n = 15, 17 and 19 were measured by direct comparison with the ground-state hyperfine interval.
TL;DR: The present review will deal only with effects characteristic of the ultraviolet region, some of them occurring solely in the near UV, but most of them being produced as well by the far UV (below 300nm).
Abstract: Because most molecules of biological importance absorb in the near-UV region (300-380 nm), a variety of biological effects may be induced by radiation of these wavelengths, but many of these are of only marginal interest for this review, since they are primarily associated with other wavelength regions (for example, photosynthesis). The present review will therefore deal only with effects characteristic of the ultraviolet region, some of them occurring solely in the near UV, but most of them being produced as well by the far UV (below 300nm). The present review concerns primarily papers published in the latter half of 1974 and throughout 1975. A summary of some work immediately prior to this period is given by Pollard [29]. A few papers in this area also appear in the report of the Squaw Valley conference of 1974 [16].
TL;DR: The results mean that the action spectrum is not simply the absorption spectrum of a chromophore carried by the photoreactivating enzyme, nor is it solely determined by the nature of the substrate photoproduct, but is at least partly determinedBy the over‐all polynueleotide structure.
Abstract: — The absolute action spectrum has been determined for photoenzymatic splitting of cyclobutadipyrimidines (“pyrimidine dimers”) from natural DNA, and from the synthetic polydeoxyribonucleotides poly(dA)·poly(dT) (forming only cyclobutadithymine) and poly(dG)·poly(dC) (forming only cyclobutadicytosine). These action spectra differ strikingly from each other, even when using the same enzyme preparations. On the other hand, the action spectrum for splitting cyclobutadithymine in natural DNA containing “dimers” of only this one type closely resembles the action spectrum for splitting the total mixture of “dimer” types in natural DNA, and is entirely different from the spectrum for splitting of the same photoproduct from poly(dA)·poly(dT). These results mean that the action spectrum is not simply the absorption spectrum of a chromophore carried by the photoreactivating enzyme, nor is it solely determined by the nature of the substrate photoproduct. It is at least partly determined by the over-all polynueleotide structure (viz. exact helical dimensions, pattern of neighboring bases to the “dimers,” or both), affecting a ground state interaction between the enzyme and substrate in the enzyme-substrate complex.
TL;DR: In this paper, a picture of the north polar F layer and the topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2) that passed over the region within a time interval of about 50 min on a magnetically quiet day.