Given a mapping f between continua.Let 2f and C(f) mean the induced mappings between hyperspaces.Relations are studied under the conditions:f is semi-open(almost open,respectively),2f is semi-open(almost open,respecti...Given a mapping f between continua.Let 2f and C(f) mean the induced mappings between hyperspaces.Relations are studied under the conditions:f is semi-open(almost open,respectively),2f is semi-open(almost open,respectively) and C(f) is semi-open(almost open,respectively).展开更多
Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction...Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.展开更多
Barge asked if each homeomorphism of a hereditarily decomposable chainable continuum has zero topological entropy and Toledo asked if a homeomorphism of a chainable continuum can always be induced by square commuting ...Barge asked if each homeomorphism of a hereditarily decomposable chainable continuum has zero topological entropy and Toledo asked if a homeomorphism of a chainable continuum can always be induced by square commuting diagram on inverse systems of finite graphs. We show in this note that if Toledos question has a positive answer then Barges question also has a positive answer.展开更多
Lattice-valued semicontinuous mappings play a basic and important role in solving the problems of L-fuzzy compactification theory,and make the previous work on weakly induced spaces and induced spaces determinatively ...Lattice-valued semicontinuous mappings play a basic and important role in solving the problems of L-fuzzy compactification theory,and make the previous work on weakly induced spaces and induced spaces determinatively generalized and strengthened.Moreover,we can describe the complete distributivity of lattices with them as well.In this paper,we give the mutually descrip- tive relation between lattice-valued semicontinuous mappings and the complete distributivity of lattices, and the construction theorems of open sets and closed sets in lattice-valued fully stratified spaces, weakly induced spaces and induced spaces(they are called S-spaces).Furthermore,we will investi- gate the structure of the co-topology of S-space,solve a series of interesting problems on product, N-compactness and metrization of S-spaces.展开更多
文摘Given a mapping f between continua.Let 2f and C(f) mean the induced mappings between hyperspaces.Relations are studied under the conditions:f is semi-open(almost open,respectively),2f is semi-open(almost open,respectively) and C(f) is semi-open(almost open,respectively).
文摘Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.
文摘Barge asked if each homeomorphism of a hereditarily decomposable chainable continuum has zero topological entropy and Toledo asked if a homeomorphism of a chainable continuum can always be induced by square commuting diagram on inverse systems of finite graphs. We show in this note that if Toledos question has a positive answer then Barges question also has a positive answer.
基金The Project Supported by National Natural Science Foundation of China.
文摘Lattice-valued semicontinuous mappings play a basic and important role in solving the problems of L-fuzzy compactification theory,and make the previous work on weakly induced spaces and induced spaces determinatively generalized and strengthened.Moreover,we can describe the complete distributivity of lattices with them as well.In this paper,we give the mutually descrip- tive relation between lattice-valued semicontinuous mappings and the complete distributivity of lattices, and the construction theorems of open sets and closed sets in lattice-valued fully stratified spaces, weakly induced spaces and induced spaces(they are called S-spaces).Furthermore,we will investi- gate the structure of the co-topology of S-space,solve a series of interesting problems on product, N-compactness and metrization of S-spaces.
