Showing papers by "The Chinese University of Hong Kong published in 1974"

Synthesis of indicator strains and density of ribonucleic acid-containing coliphages in sewage.

Abstract: Escherichia coli strains freshly isolated from natural sources are inefficient indicators of coliphages present in sewage Four E coli strains recently isolated from clinical specimens were mutagenized to obtain lac(-) mutants Such mutants were infected with an F'lac(+) sex factor of E coli K-12 Pairs of isogenic lac(-) and lac(-)/F'lac(+) strains were used as indicators of coliphages present in sewage, and it was found that such strains can be effectively used for a direct and almost selective enumeration of F-specific coliphage contents of sewage samples Serological tests were applied to a number of F-specific phages isolated All the isolates that were tested fell into two distinguishable antigenic classes: members of one class being related to ribonucleic acid (RNA) phage MS2 and those of the other being related to another RNA phage, namely, Qbeta MS2-related phages have been found to be more widely distributed than the Qbeta related phages Most habitats sampled were found to yield only one or the other kind of phage Single-stranded deoxyribonucleic acid-containing F-specific phages were not detectable by the methods employed by us

A testing of some dynamic kinetic equations

Abstract: The acid-catalysed iodination of acetone in aqueous solution was used to test three dynamic kinetic equations. The Freeman and Carroll treatment yields the most satisfactory results.

The effect of body lean and status of an interviewer on the non‐verbal behavior of japanese interviewees

Abstract: This study was a preliminary investigation of non-verbal communication in Japanese subjects. Sixteen males and sixteen females were interviewed by one of two male confederates. The confederates were described and dressed as either high or equal status persons. They assumed either a forward lean or a backward lean during the four minute interview. Tape and video recordings were analyzed across a wide spectrum of non-verbal behaviors emitted by the subjects during the interview. Both status and body lean variables affected a variety of dependent measures, particularly for female subjects. A factor analysis of the non-verbal behaviors produced some unexpected results which have implications for similar studies done in other cultures.

Attendance Regularity of Adult Learners: An Examination of Content and Structural Factors.

Abstract: This exploratory study investigated attendance regularity of adult learners enrolled in the Chinese University extramural courses from the perspective of content and structural processes. Corre lational analysis of questionnaire data revealed that degree of course understanding, need-fulfillment, approachability of the instructor, and amount of informal and formal interaction were all positively and significantly related to attendance rate whereas sociability of classmates and attendance rate were negatively and significantly related. F-tests from step-wise multiple linear regres sion analysis indicated that none of these factors made any special contribution in explaining attendance, though their relative shares could still be detected.

N-methyl-N′-nitro-N-nitrosoguanidine and hydroxylamine induced mutants of the rII region of phage T4

Abstract: rII mutations of bacteriophage T4 were induced by in vivo treatment with N-methyl-N′-nitro-N-nitrosoguanidine (NG) and in vitro treatment with hydroxylamine (HA). All the NG induced mutations were mappable to small segments of the rIIA cistron and all except one were also highly revertible by 2-aminopurine (AP) treatment. From these observations, it is concluded that treatment of T4 with NG induces only transitions and contrary to its effects on E. coli, in T4, NG does not induce any deletions. Spectra of HA and NG induced mutants of the rIIA cistron were compared. Both mutagens seem to be more effective in inducing mutations nearer the two extremities of this cistron and very few in the middle. This asymmetric effect has been seen to be more pronounced in case of NG than in the case of HA.

On supports of semigroups of measures

Abstract: supp fi is the support of \i e P(S). In the case in which S is commutative it was shown by Glicksberg in (4) that S(T) is an algebraic group in S if F is an algebraic group. For a general semigroup S, Pym (7) considered F = {n}, r\ being an idempotent, and established that S(V) is a topologically simple subsemigroup of S, i.e. every ideal of S(T) is dense in S(F). In this note we prove that if F is a simple subsemigroup of P(S) (a semigroup is simple if it contains no proper ideal) which contains an idempotent then S(F) is a topologically simple subsemigroup of S. We also give an example to show that our conclusion (hence also Pym's) is best possible in the sense that S(T) is not simple in general. Next, if Sis jointly continuous and supp F = S(F) (the bar denotes closure), we can then obtain that supp F must be simple if F is assumed simple but not necessarily containing an idempotent. In other words, (Theorem 4) for a jointly continuous semigroup S, the support of a simple subsemigroup of P(S) is a compact simple subsemigroup of S. This fills a lacuna in the literature. In fact it was first stated by Lin as a corollary of the following (5, Theorem 3): " If £ is a closed subsemigroup of P(S), then the minimal ideal K(svpp I ) of supp S is the support of the minimal ideal K(L) of £." Unfortunately the proof of this statement given in (5) contains a gap since the set

Improved logic model for thyristor

Abstract: A method of developing a logic model to simulate the thyristor is described. Examples are given to illustrate the use of the model in invertor simulation

Decay instability of cirularly polarized waves into cirularly polarized and Langmuir waves in a magnetized plasma

Abstract: A study was made of a parametric instability in a magnetized plasma in which an electromagnetic pump wave of either right- or left-hand circular polarization decayed into a Langmuir wave and another circularly polarized wave, all with wave vectors colinear with the external magnetic field. The analysis was based on a multiple-time- scale perturbation expansion of the fluid equations, incorporating the effects of temperature, collisions, and the spatial variation of the pump wave. The threshold values of the pump field intensity required for instability and the growth rates above threshold were calculated. (auth)

Stimulatory effect of Leonurus artemisia (i-mu ts'ao) on the contraction of human myometrium in vitro.

Abstract: Leonurus artemisiae, l'agripaume chinoise, est applicable comme emmenagogue selon une tradition millenaire chinoise. L'element efficient est la leonurine. L'extrait de leonurine par l'alcool methanolique acidifie a un effet stimulant dans la myometrie humaine in vitro.

Backscattering and Absorptive Parametric Instabilities Involving the Lower Hybrid Mode in a Magnetized Plasma

Abstract: The theories of two decay-type parametric instabilities involving the lower hybrid mode in a magnetized plasma are presented. In the first of these, a pump wave of ordinary polarization causes the growth of a backward propagating transverse wave and a longitudinal lower hybrid wave, all with wave vectors perpendicular to the external magnetic field. The second instability concerns the parametric excitation of the upper hybrid and the lower hybrid modes.

Elementary and Composite Particles in Asymptotically Free Gauge Theories

Abstract: We demonstrate that in asymptotically free gauge theories the wave-function renormalization constants for spin-1/2 fields do not vanish. (The scalar fields, if incorporated, also have this property.) However, there exists a subclass of such theories where the $Z'\mathrm{s}$ for the gauge fields themselves tend to zero in the limit of infinite cutoff. These features are shown to be gauge-independent. This suggests the potentiality of constructing asymptotically free strong-interaction theories in which the only elementary fields are "quarks" and all other hadrons are bound states.

On the boundary of algebraic radicals in topological semigroups

Abstract: A topological semigroup is a semigroup with a Hausdorff topology in which multiplication is continuous in both variables. In what follows S will denote a topological semigroup. We let A be any subset of S. The algebraic radical of A is defined to be the set {xCS]xkEA for some integer k_->l} and is denoted by R(A). In [3], K. P. SHUM and C. S. Hoo studied some properties of the algebraic radicals of ideals in compact abelian semigroups. In this paper, we are going to give further investigations on the algebraic radical of an ideal A of S. We find that the boundary of the algebraic radical of an open ideal A of S is closely related with a compact group in S. But in general, the structure of such a compact group is still not known to the author. Here only the existence of a compact group on the boundary of R (A) will be discussed. We list here several definitions which will be frequently used in this paper. Let A be any subset of S, then J(A) = A U SA UASU SAS is called theprincipal ideal generated by A. If S is abelian, then an ideal P of S is said to be prime if ab CP implies that a EP or b CP. An ideal Q of S is said to be primary if ab EQ implies that a E Q or there exists an integer k => 1 such that b k E Q. If S is a semigroup without zero, then S is simple if S does not properly contain an ideal. In an abelian semigroup S, an ideal Q of S is primary if and only if R(Q) is a prime ideal of S, cf. [3]. Throughout, we use cl (C) to denote the closure of the set C, C' for the complement of C and B(C) for the boundary of C. The reader is referred to [4] for other unstated definitions and notations. THEOREM 1. Let S be a connected abelian semigroup with unity and let A be an open ideal of S. Then A is a primqry ideal if and only if the boundary B(R(A)) of R(A) is a subsemigroup of S.

Dual variational principles with delayed argument

Abstract: This work develops dual or complementary variational principles for functional with delayed argument. Local conditions for the existence of a pair of dual extremum principles are given. It extends the results of B. Noble to the case with delayed argument.

A New and Simple Three-Phase Thyristor Inverter for Variable Frequency Operation

Abstract: A new three-phase inverter circuit is described and analyzed for the condition of an inductive load. The circuit does not require an auxiliary supply or any auxiliary thyristors to assist commutation. All commutation capacitors are placed across the dc side but are used in the same way as capacitors that are normally used for ac side commutation. The output voltage of the inverter is a quasi sine wave controlled by a simple firing circuit. The author was a visiting Research Fellow with the Department of Electrical Engineering and Electronics, the University of Manchester Institute of Science and Technology, Manchester, England.