scispace - formally typeset
Search or ask a question

Showing papers by "Hungarian Academy of Sciences published in 1973"


Journal ArticleDOI
04 Jul 1973-Nature
TL;DR: Conditions are worked out for the isolation of streptomycin-resistant tobacco cell lines, from which diploid fertile plants carrying the streptomecin- resistant character, were regenerated and seedlings grown from seeds of self-fertilized resistant Str-r1 plants were resistant.
Abstract: THERE are few reports of the isolation of biochemical mutants from cultured plant cells1–3. We know of none describing plants which have been regenerated from these mutant cell lines and which still carry the mutant trait. We have worked out conditions for the isolation of streptomycin-resistant tobacco cell lines, from which diploid fertile plants carrying the streptomycin-resistant character, were regenerated. Seedlings grown from seeds of self-fertilized resistant Str-r1 plants were also resistant. The progeny obtained from crosses of Str-r1 plants and streptomycin sensitive (Str-s) plants showed non-Mendelian, uniparental transmission of the resistance trait.

450 citations


Journal ArticleDOI
TL;DR: A drawing strategy is explained which applies to a wide class of combinatorial and positional games and when applied to n -dimensional Tic-Tac-Toe, it improves a result of Hales and Jewett.

346 citations


Journal ArticleDOI
TL;DR: In this paper, the minor and major axes of track-pits of nuclear particles registered in dielectric solids are gradually varying in the course of the etching process.

240 citations


Journal ArticleDOI
TL;DR: The theory presented in this paper is based to a large extent on recent results of the author concerning logarithmic concave measures on two stochastic programming decision models, where the solvability of the second stage problem only with a prescribed (high) probability is required.
Abstract: Two stochastic programming decision models are presented. In the first one, we use probabilistic constraints, and constraints involving conditional expectations further incorporate penalties into the objective. The probabilistic constraint prescribes a lower bound for the probability of simultaneous occurrence of events, the number of which can be infinite in which case stochastic processes are involved. The second one is a variant of the model: two-stage programming under uncertainty, where we require the solvability of the second stage problem only with a prescribed (high) probability. The theory presented in this paper is based to a large extent on recent results of the author concerning logarithmic concave measures.

182 citations


Journal ArticleDOI
TL;DR: In this article, the crossing number problem is formulated as a set of crossing number problems, and solved in a linear fashion, with a fixed number of crossings per number of columns.
Abstract: (1973). Crossing Number Problems. The American Mathematical Monthly: Vol. 80, No. 1, pp. 52-58.

177 citations


Journal ArticleDOI
TL;DR: In this paper, the smallest integer m for which the following statement is true was shown: if a G graph has at least m vertices, then either G contains a Cn (cycle of length n) or G contain a Cp (cyclic length n), then R(Cn, C2r) = n + r − 1.

131 citations


Journal ArticleDOI
TL;DR: Questions of whether or not certain R are r -Ramsey where B is a Euclidean space and R is defined geometrically are investigated.

115 citations


Journal ArticleDOI
TL;DR: Let L Kinp be a p-chromatic graph and e be an edge of L such that L - e is (p-1)-chromatic and G^n is a graph of n vertices without containing L but containing K"p.

103 citations


Journal ArticleDOI
TL;DR: The mechanism of action of papain is reconsidered and it is concluded that the acylation and deacylation steps are not symmetrical processes, and they are one-encounter type reactions.
Abstract: The reaction of the thiol group of papain with chloroacetamide, iodoacetamide, d- and l-2-bromopropionamides was studied. In the acidic pH-range the reaction rate is higher than expected for an ordinary SH-group and shows a double-sigmoid pH-rate profile. In addition to the already described pKa of 8.5, we found a pKa of 4.0. This indicates that in the pH-range where the enzyme is catalytically active the thiol group of Cys-25 interacts with some amino acid side chain, presumably with the imidazole group of the neighboring His-159. In the light of the X-ray diffraction studies (Drenth et al., 1971), it is probable that the anomalous PKa of His-159 is due to its interaction with Trp-177. The comparison of the pH-rate profiles of d- and l-2-bromopropionamide reactions indicates that there is no sifgnificant alteration in the geometry of the active site around pH 4, whereas at slightly alkaline pH structural changes can be observed. 2H2O has no effect on the rate constants of the alkylation reaction. This rules out the possibility of general base catalysis by the imidazole group of His-159. The experimental data indicate that the dissociated thiol group forms an ion pair with the protonated imidazole group. On the basis of the formation of thiolate-imidazolium ion pair, the mechanism of action of papain is reconsidered. It is concluded that the acylation and deacylation steps are not symmetrical processes, and they are one-encounter type reactions. The interaction between His-159 and Trp-177 may be important in the catalysis.

103 citations


Journal ArticleDOI
TL;DR: In this article, the role of hexatrienes as intermediates of aromatization has been evaluated in the case of different hexadiene isomers in the presence of hydrogen in the gas phase.

74 citations


Journal ArticleDOI
TL;DR: 5HT and dopamine can be regarded as transmitter or modulator substances in the CNS, 5HT, dopamine, and noradrenaline, and in the heart.

Journal ArticleDOI
TL;DR: A number of temperature-sensitive and lysis-deficient mutants were isolated from a bacteriophage of Rhizobium meliloti and functions were classified in relation to the eclipse and latent period.

Journal ArticleDOI
TL;DR: In this article, the maximum number of edges a digraph can have if it does not contain and L i as a subgraph and has given number of vertices was studied.

Journal ArticleDOI
TL;DR: In this article, the spin projected Hartree-Fock equations are derived and discussed in the general (many λi) case, based on the corresponding generalized Brillouin theorem, substituting in its expression a spin projected DODS Slater determinant as a linear combination of determinants.
Abstract: The (spin projected) extended Hartree-Fock equations are derived and discussed in the general (“many λi”) case. The derivation is based on the corresponding generalized Brillouin theorem, substituting in its expression the spin projected DODS Slater determinant as a linear combination of determinants. The expressions obtained for the elements of the different matrices ecd (c = a or b, and d = a or b) occurring in the equations are analyzed. The transformation of the equations into the form of a pseudoeigenvalue problem and the LCAO form of the equations are given, too. Finally the relation to the Goddard's GF equations is discussed in detail.

Journal ArticleDOI
TL;DR: The isolation of a 5-bromodeoxyuridine-resistant (BUdR) cell line from callus culture of haploid Nicotiana tabacum L. cv.

Journal ArticleDOI
05 Dec 1973-Nature
TL;DR: A method has been developed for the isolation of nitrogenase mutants of Rhizobium meliloti for the study of genes regulating the synthesis of nitrogen enzyme in bacteroids within the plant host.
Abstract: THE enzyme system known as nitrogenase is responsible for conversion of elementary nitrogen in microbial-plant symbiotic nitrogen fixing associations. A method has been developed for the isolation of nitrogenase mutants of Rhizobium meliloti for the study of genes regulating the synthesis of nitrogenase. This type of ineffective mutant cannot be selected directly since nitrogenase is only synthesised in bacteroids within the plant host.

Journal ArticleDOI
TL;DR: Normal and transformed baby hamster kidncy (BHK) cells attach to Falcon polystyrene with the same first order rate constant and recovery of adhesiveness of trypsin-trcated cells is inhibitcd by cycloheximidc.
Abstract: Normal and transformed baby hamster kidncy (BHK) cells attach to Falcon polystyrene with the same first order rate constant. The longer the cclls arc attached to the bottlcs, thc more difficult they are to rcmovc. Sulfhydryl (--SH) binding rcagcnts inhibit both the attachment of BHK cells and the increase in adhesive strength of attached cells. Attached BHK cells bind fewer molecules of [1-14C]N-cthylamleimide (an --SH binding reagent) than do suspendcd cells. Incubation of cells with high concentrations of trypsin results in a reversible loss of cell adhcsivcness. Thc recovery of adhesiveness of trypsin-trcated cells is inhibitcd by cycloheximidc.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the existence of a Kr(t) can be verified by dividing n vertices into r-1 almost equal groups and connecting the points in different groups.
Abstract: Every graph appearing in this note is a finite edge graph without loops and multiple edges. Denote by G(n, m) a graph with n vertices and ni edges . K r (t) denotes a graph with r groups of t vertices each, in which two vertices are connected if and only if they belong to different groups . By dividing n vertices into r-1 almost equal groups and connecting the points in different groups one obtains a graph on n vertices with ((r 2)/2(r 1) + u (1)) 11 2 edges which does not contain a Kr(l) . On the other hand, it was shown by Erdős and Stone [7] that ((r 2)/2(r 1) + s) n2 (e > 0) edges assure already the existence of a Kr(t), where t -~ oo as n -p co . This result is the inost essential part of the theorems on the structure of extremal graphs, see e .g. [3], [4], [6], [9] . Let us formulate the result of Erdős and Stone more precisely . Given n, r and e, put rn = [((r-2)/2(r-1)+e)n2] ([x] denotes the integer part of x) and define g(n, r, e) = min {t : every G(n, in) contains a K r (t)} .

Journal ArticleDOI
TL;DR: Any finite information source is given a graph structure, in which two vertices are adjacent whenever the two corresponding source letters are distinguishable by the coder-decoder pair, and if the associated graph is not complete, an \varepsilon -code for the source can be constructed in two steps.
Abstract: Any finite information source is given a graph structure, in which two vertices are adjacent whenever the two corresponding source letters are distinguishable by the coder-decoder pair. Usual sources correspond, therefore, to complete graphs. If the associated graph is not complete, however, an \varepsilon -code for the source can be constructed in two steps: in the first, distinct codewords are given to distinguishable letters only; in the second step, a similar encoding is carried out for the complementary graph, in which distinguishable letters become indistinguishable and the converse. A particularly simple case shows up when nonadjacency is an equivalence relation among the vertices of the graph: each class of nondistinguishable letters can then be considered as a letter in a coarser source alphabet. The two-step procedure is then particularly intuitive. A problem arises when this procedure does not destroy optimality of the resulting \varepsilon -code; some partial results are given in this direction. The results obtained are largely based on some graph-theoretical ideas and tools.

Journal ArticleDOI
TL;DR: In this paper, the adsorption of Cl− ions has been studied by a tracer method in the course of electrosorption in the case of Cu2_ ions on platinized platinum.

Journal ArticleDOI
TL;DR: Two phosphido cobalt carbonyl cluster Co(CO)6P2 and Co3CO9PS have been described and characterized in this article, and two Co3Co9PS has been characterized.

Journal ArticleDOI
TL;DR: The variations of the 5 HT level in snails can be considered partly as the consequence of the change of the activity, but on the other hand the serotonin level can play a role in the determination of theactivity of the animal.

Journal ArticleDOI
TL;DR: Among the eight species of the fern genus Dryopteris which have been recorded from Kenya (East Africa), the group of D. inacqualis, D. pentheri and D. schimperana is regarded as critical, and the hypothesis that the latter is an allotetraploid derived from the diploids 6 and 7 is supported.
Abstract: Among the eight species of the fern genus Dryopteris which have been recorded from Kenya (East Africa), the group of D. inacqualis, D. pentheri and D. schimperana is regarded as critical. There is no agreement among experts as to whether D. inaequalis s. str. is restricted to South Africa and whether it should be separated specifically from D. pentheri Chemical and, as far as possible, cytological investigations of available material showed that the following taxa of Dryopteris occur in Kenya (ploidy in brackets) : 1. D. athamantica (2 × );2. D. callolepis (4 × ); 3. D. inaequalis (4 × ); 4. D. kilenzensis (2 × ); 5. D. manniana (4 × ); 6. D. pentheri (2 × ); 7. D. schimperana (2 × ); 8. D. sp. RBF-71/885 (TR-330.5) (4 × ); 9. D. squamiseta(ploidy not determined). The nomenclature of the four critical taxa, 3, 6, 7 and 8 is provisional. For comparison, two taxa from the Canary Islands, 10. D. ‘dilatata’ (4 × ) and 11. D. oligodonta (2 × ) were also investigated. Among the nine taxa from Kcnya, two (4 and 9) did not contain any phloroglucides. Dryopteris kilomensis must be regarded as one of the few representatives of the genus Dryopteris which lacks such compounds. On the other hand, the negative result for 9 is in agreement with the fact that this species has recently been transferred to a new genus Nothopevanema. The following three new compounds havc been isolated: Trisaspidinol (8), from D. inaequalis; Pentherin-I (not quitc pure) and Pentherin-I1 (hypothetical partial formula 25), from D. pentheri. Pentherin-I is also present in D. sp. RBF-71/885. Chemical and cytological results are compatiblc with the hypothesis that the latter is an allotetraploid derived from the diploids 6 and 7. The chemical patterns of 6, 7 and 8 show similarities to that of D. manniana, which in turn also shows similarities to the European D. filix-mas. Dryopteris ‘dilatata’ from the Canary Islands is chemically different from Europcan D. dilatata s. str. in lacking para-aspidin, while D. oligodonta gave results rather different from D. inaequalis or other East African species, and also from known European taxa.

Journal ArticleDOI
TL;DR: In this paper, the molecular structure of sulphonyl fluoride in the vapour state was studied by electron diffraction and the following geometrical parameters (r a structure) have been obtained: r(C-H) = 1.093±0.010A, r(S-O) =1.410± 0.003A, R(SF) = 2.561 ± 0.004A, S-C) = 98.2±1.5°, ∠-S-F = 106.1 ± 1.4°

Journal ArticleDOI
TL;DR: In this article, it was shown that the sintering of a platinum black catalyst was most affected by the presence of hydrogen which caused considerable growth in crystallite size, and it was possible that apparent effects of reaction and thermal treatment may have, in previous work, been caused by pre-treatment in hydrogen.
Abstract: Counter claims appear in the literature on the effects of the particle size, sintering and pre-treatment of a catalyst on its activity. We have investigated these by studying a platinum black catalyst and the way in which helium, hydrogen, air, oxygen and thermal cycling affect the particle size as seen in the electron microscope. By making a logical sequence of experiments it has been possible to show that the sintering of the catalyst was most affected by the presence of hydrogen which caused considerable growth in crystallite size. It thus seems possible that apparent effects of reaction and thermal treatment may have, in previous work, been caused by pre-treatment in hydrogen.

Journal ArticleDOI
G. Lázár1, G. Borbély1, J. Udvardy1, G. Premecz1, G. L. Farkas1 
TL;DR: In protoplasts isolated from tobacco leaves and incubated in 0.7 M mannitol for 24 h, the ribonuclease (RNAase) level increased 12- to 15-fold during incubation, and various inhibitors of protein synthesis prevented or reduced the increase in RNAase activity.

Journal ArticleDOI
TL;DR: Two acridine drugs, Acranil and quinacrine, were found to be effective, the former being almost as protective as tilorone and the latter less so, and both induced an interferon-like substance which could be detected in the serum of treated mice.
Abstract: Several drugs with certain structural similarities (tricyclic ring system with dialkylaminoalkyl side chains) to tilorone, a potent interferon inducer, were screened for antiviral activity in vivo. Two acridine drugs, Acranil and quinacrine, were found to be effective, the former being almost as protective as tilorone and the latter less so. Both agents induced an interferon-like substance which could be detected in the serum of treated mice. The concentration of the inhibitory factor in the serum was highest after exposure to tilorone, followed in turn by Acranil and quinacrine, based on the administration of equal weights of drugs. Both tilorone and Acranil induced lower levels of circulating interferon-like substance in Balb/c mice than in other strains of mice. The serum factor induced by Acranil was shown to be stable at pH 2.

Journal ArticleDOI
TL;DR: A family T of k-subsets of an n-set such that no more than r have pairwise fewer than s elements in common is maximum (for sufficiently large n) only if T consists of all the k-sets containing at least one of r fixed disjoint s- Subsets.


Journal ArticleDOI
TL;DR: Strains of Newcastle disease virus (NDV), which were good or poor inducers of interferon in chick cells, occurred in all virulence groups of this virus.
Abstract: Summary Strains of Newcastle disease virus (NDV), which were good or poor inducers of interferon in chick cells, occurred in all virulence groups of this virus. Mesogenic and velogenic strains which killed the embryo rapidly were better interferon inducers in embryonated egg than were the lentogenic strains. Identical and low sensitivities to interferon were shown by an interferon-inducing vaccine strain and a non-inducing and highly virulent strain. Measurements made when various strains were used to infect either normal or interferon-pre-treated cells showed that the absence of interferon production was not due to the inhibitory effect of virus infection on cellular protein synthesis. It is suggested that infective NDV synthesizes two kinds of inhibitory protein during infection. One of these inhibits the synthesis of the interferon protein and in consequence the majority of strains do not induce interferon in chick cells. The second protein is induced mainly by mesogenic and velogenic strains and may be responsible for inhibiting cellular protein synthesis.