Search

Many undergraduate students find the production of an extended piece of academic writing challenging. This challenge is more acute in the sciences where production of extended texts is infrequent throughout undergraduate studies. This paper reports the development of a new English for Academic Purposes (EAP) workshop and associated resources for third year undergraduate chemists to support their dissertation module. The workshop is designed to utilise a searchable database of student texts (a corpus) developed as part of the FOCUS project at Durham University. This novel use of data-driven learning (DDL), common in second language pedagogy, transfers well to the chemistry classroom as the processes of research and discovery (of words rather than chemicals) involved in DDL parallel similar processes in chemistry research. Our workshop and online consolidation activities have been positively evaluated by both staff and our current cohort of students. The project is being rolled out across other departments at Durham as well as the corpus tool being utilised at other UK HEIs. This corpus-based approach to academic writing in chemistry offers a unique perspective on the interplay between language and scientific literacy.

Robert Edward Bell, a distinguished Canadian physicist, Fellow of the Royal Society, former President of the Royal Society of Canada and former Principal and Vice- Chancellor of McGill University, died on 1 April 1992 in Vancouver, Canada, after a long and difficult illness.

Quadtrees constitute a hierarchical data structure which permits fast access to multidimensional data. This paper presents the analysis of the expected cost of various types of searches in quadtrees -- fully specified and partial-match queries. The data model assumes random points with independently drawn coordinate values. The analysis leads to a class of "full-history" divide-and-conquer recurrences. These recurrences are solved using generating functions, either exactly for dimensiond=2, or asymptotically for higher dimensions. The exact solutions involve hypergeometric functions. The general asymptotic solutions rely on the classification of singularities of linear differential equations with analytic coefficients, and on singularity analysis techniques. These methods are applicable to the asymptotic solution of a wide range of linear recurrences, as may occur in particular in the analysis of multidimensional searching problems.

It is well known that removal of the pituitary gland is followed by alterations in a number of metabolic processes. It was therefore thought of interest to determine whether these alterations involved any changes in certain immune processes, since very little is known at present of the factors controlling them. Our immunity experiments were made on rabbits and consisted in determining the complement content, the bactericidal power and the opsonic activity of the rabbits' serum.

A study of 59 isolates of Bartonella henselae reveals relatively limited diversity among those of human origin ( n = 28). Either of two distinct alleles of both gltA and 16S ribosomal DNA (rDNA) was found in all isolates, with a high level of congruity between 16S and gltA inheritance among proven human pathogens. Human isolates from all over Eastern Australia were most commonly 16S rDNA (Bergmans) type I, with the same gltA allele as the type strain (Houston-1). Comparable feline isolates were more commonly 16S type II, with less congruity of inheritance between 16S and gltA alleles. Previously described arbitrarily primed PCR and Eag I- Hha I infrequent restriction site PCR fingerprinting techniques separated Bartonella species effectively but lacked discriminating power within B. henselae. Examination of the 16-23S intergenic spacer region revealed for several strains several point mutations as well as a repeat sequence of unknown significance which is readily detected by Hae III restriction fragment length polymorphism analysis. The bacteriophage-associated papA gene was present in all isolates. Enterobacterial repetitive intergenic consensus PCR proved to be a useful and robust typing tool and clearly separated human isolates (including imported strains) from the majority of feline isolates. Our data are consistent with published evidence and with previous suggestions of intragenomic rearrangements in the type strain and suggest that human isolates come from a limited subset of B. henselae strains. They strengthen arguments for careful exploration of genotype-phenotype relationships and for the development of a multilocus enzyme electrophoresis and multilocus sequence typing-based approach to the phylogeny of B. henselae .

The discovery of the NP-Complete problems has created a vigorous industry producing proofs of NP-Completeness. But does NP-Completeness really imply intractability of interesting instances? This question seems to divide the Computer Science community into two camps, the pessimists who believe that NP-Complete problems require exponential resources and are therefore intractable and the optimists who expect a subexponential algorithm to emerge eventually. There is however a viable third belief, namely that the resources required do rise exponentially but slowly enough for large practical problems to be tractable. A number of algorithms have been reported, using an approach more sophisticated than the obvious search of all possible solutions to achieve run times significantly less than the naive approach would suggest (Iwama, 1987; Schroeppel and Shamir, 1981; Stearns and Hunt, 1990; Tanaka, 1991) but on a sequential machine these do not yet seem to solve real large problems in reasonable time. On the other hand the naive approach to most NP-Complete problems parallelises easily but yields an algorithm which is too slow even on large parallel machines. However, where the sophisticated algorithms can be parallelised,the result may well be that very large problems which have appeared intractable can be solved quite easily with machines which exist today and will be cheap tomorrow. One interesting development in this direction is described by Ferreira (this volume).

An operation op of arity k on ℕ, i.e. a function op: ℕk → ℕ is linear time Turing computable (for short, LTTC) if it is computable in linear time on a Turing machine (for usual binary or dyadic notation of integers). Let + and Conc respectively denote usual addition of integers and concatenation (of their dyadic notations). A RAM which uses only arithmetical operations of a set I is called an I - RAM. An LTTC-RAM is a RAM which only uses LTTC operations.

The sum of the absorption, incoherent, and thermal inelastic scattering cross sections of natural titanium has been measured at 293 K for three neutron velocities in the range 6–8 m/s. They agree with values to be expected on the basis of an inverse velocity extrapolation from measurements near thermal neutron velocities.

Alternating Turing machines with restrictions preventing them from returning to a previous configuration model games with rules enforcing such a restriction, for instance, the Chinese version of Go. Such restrictions do not affect the time complexity of problems for alternating Turing machines but space S on a machine with the restriction is equivalent either to time or to space exponential in S on a normal alternating machine, depending on the precise nature of the restriction.

Measurements have been made of the thermal neutron fluxes at various distances from a point source of 14-MeV neutrons embedded in three large shields. The first shield consisted of a 24-m/sup 3/ assembly of solid concrete building blocks of density 2.2 g/cm/sup 3/ and gave an attenuation length of 14.1 + or - 0.7 cm at a distance of 150 cm from the source. The second shield was a layered assembly of wood and concrete blocks with a mean density of 1.92 g/cm/sup 3/ and gave an attenuation length of 15.7 + or - 0.7 cm at the same distance. The third assembly consisted of a cube of side 61 cm of steel surrounded by concrete blocks; at a distance of 120 cm from the source it gave an attenuation length of 9.3 + or - 0.4 cm.)

The experimental work on the radioactivity decay of the neutron between 1948 and 1981 is reviewed in the light of the developments in our understanding of the beta decay process. Whereas the early work was primarily concerned with the nature of the decay the more recent experiments have concentrated on an accurate determination of the ratio of the coupling constants involved in the process. The progress has been impressive but our knowledge of the half-life is still disappointingly imprecise.

The amount of store necessary to operate a dynamic storage allocation system, subject to certain constraints, with no risk of breakdown due to storage fragmentation, is considered. Upper and lower bounds are given for this amount of store, both of them stronger than those established earlier. The lower bound is the exact solution of a related problem concerning allocation of blocks whose size is always a power of 2.

The intensity of ultra cold neutrons transmitted along a copper tube has been calculated by Monte Carlo techniques and compared with experimental intensities and with pure diffusion theory calculations. The possibility of focussing ultra cold neutrons by using a conical tube is also illustrated by this technique.

SummaryThe injection of adrenaline hydrochloride into mature female mice is able to inhibit the occurrence of oestrus.The injection of adrenaline hydrochloride into immature female mice prevents the onset of sexual maturity.Adrenaline does not interfere with the action of α-hormone (œstrin) on the uterus and vagina; it has an inhibitory effect on the action of gonadotropic hormones (prepared from pregnancy urine) on the ovary.I should like to thank Mr P. G. Marshall for the supply of gonadotropic preparation from pregnancy urine used in these experiments.

Testosterone propionate produces inhibition of the reaction to oxytocin of the rabbit's uterus and some progestational proliferation. The relative intensities of these two effects is different from that brought about by progesterone; the inhibitory action on the muscle may be obtained when little or no progestational proliferation of the endometrium is present. The expenses of this investigation have been defrayed by a grant from the Medical Research Council.