Showing papers by "Durham University published in 1969"

Estimation of Finite Mixtures of Distributions from the Exponential Family

Abstract: General “successive substitutions” iteration equations are developed for obtaining estimates for finite mixtures of distributions from the exponential family. These, in general, correspond to relative maximums of the likelihood function. It is assumed that the number of distributions is known, and that the mixtures are from distributions of the same type, but with different parameter values. The particular equations for the Poisson, binomial, and exponential distributions are given, as well as examples of the results of the procedure for each distribution. From the examples tried, it was observed that the likelihood function increased at each iteration. Graphs of the asymptotic variances of the estimates are given, and two sampling experiments comparing estimates obtained by this scheme with moment estimates are also given.

A Stochastic Analysis of the Maintenance Behaviour of Skylarks

Abstract: The paper attempts to describe the maintenance behaviour of Skylarks Alauda arvensis using conventional qualitative and quantitative descriptive frameworks and, as a new technique, random event series analysis. It is based on behaviour records of individually marked birds which were observed in the field for extended periods. Starting from frequency analysis and using random signal analysis as a stepping stone the rationale of random event analysis is briefly explained. Some of the problems involved in considering behaviour sequences as signals and the implications of viewing animals as black box systems, particularly when only the output i.e. behaviour, is available, are reviewed. The limitations of random event analysis for dealing with non-stationarity and non-linearity are considered. A qualitative description of the maintenance behaviour follows. Some information is given on the behavioural responses to environmental stimuli, particularly to the arrival of the observer. The sequential organisation of the behaviour in terms of transition probabilities is presented next. Deviations from a null order model are found when the behaviour events are separated by less than a minute and some of the implications are briefly mentioned. In a special subsection the sequential organisation of preening is similarly treated but on the basis of too few data to give any conclusive result. Then the distribution of intervals between the various behaviour patterns are given in a matrix form and some indications of deviations of random occurrence are found and discussed. A matrix of inter-behaviour correlations based on the frequency of behavioural events per various time units is presented and the finding that the duration of time units affects the correlations is discussed. In this context some correlation coefficients with non-maintenance behaviour are given and they support the idea that the comfort patterns may be related to a sleep syndrome. Matrices of auto-and cross-correlation functions and the related intensity functions support the view that frequency correlation matrices are not capable of imparting information on an important characteristic of interbehaviour relationships, the time dependent dynamic responses. Lastly, the transformation of the correlation function, the auto- and cross-spectra, are presented for comfort behaviour and flying. These support the notion that comfort behaviour is affected by rhythmical processes while flying is shown in an essentially random fashion. Little systematic relationship was found between comfort behaviour and flying as reflected by the transfer and coherence functions. In the discussion the various quantitative descriptive formats are briefly discussed and some of the objections to the use of advanced analytical techniques are dealt with. The implications of these techniques for models of behaviour are discussed and the complexity of interactions between the causal processes leading to behaviour are stressed. Finally some suggestions for future work are offered.

Relations between dynamic mechanical properties and melting behavior of nylon 66 and poly(ethylene terephthalate)

Abstract: Nylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at −140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawing. The form I and form II types of melting behavior are also found in poly(ethylene terephthalate); the interconversions and thermal behavior of the forms are analogous to the nylon 66 case. In poly(ethylene terephthalate), the β relaxation at −40 to −60°C is present only when form I melting behavior is found. Conversion to form II melting behavior by annealing or drawing (80°C) again causes the relaxation to disappear. No β relaxation was found in amorphous polymer. The γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) can therefore be associated with the crystalline structure responsible for form I melting behavior. Form I melting behavior has been associated with foldedchain crystals based on previous work. It is therefore postulated that the γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) are associated with motions in the chain folds. This assignment is not inconsistent with the change in the γ dispersion of nylon 66 with the number of backbone CH2 units, since these will affect the fold structure.

The Organization of the Legion: The First Cohort and The Equites Legionis

Abstract: It is generally recognized that the first cohort of a legion in the Principate was larger than the other nine cohorts It consisted of five centuries, each double the size of each of the six centuries of cohorts II to X Literature, epigraphy and archaeology all agree over this point Vegetius, in the Epitoma rei militaris, probably quoting a third-century source, says that the first cohort was twice as large as each of the other cohorts, but he disagrees with himself over the number of men in the cohort At one stage (II, 6) he states that the first cohort had 1,105 pedites and 132 equites and was called a cohors miliaria, compared to the 555 pedites and sixty-six equites of each of the other nine cohorts, cohortes quingenariae But two paragraphs later (II, 8) this number has been reduced to 1,000 This is made up of 400 men in the first century, 200 in the second, 150 in the third and fourth and 100 in the fifth Although none of Vegetius' figures is to be trusted, his basic point remains—the first cohort of a legion was double in size This is supported by epigraphic evidence III, 6178, dated to about AD 134, lists, by cohort, the soldiers of legio V Macedonica discharged at one time The first cohort contains at least forty names, the second seventeen, the third at least fourteen, the fourth at least ten and the ninth at least twelve A similar situation is found on III, 14507, a laterculus, which is a dedication by veterans of VII Claudia discharged in 195 In this case the first cohort discharged forty-seven men, the second twenty-two and the third eighteen These two inscriptions point to the fact that the first cohort was about twice as large as each of the other nine Excavations at Inchtuthil have provided the most eloquent testimony Here the barracks of the first cohort, ten in number, compared to the six of each of the other nine cohorts, have been revealed, in association with five large centurions' houses, situated next to the headquarters building This is where it is placed by ‘Hyginus’ in the liber de munitionibus castrorum (3; 4), probably dated to the sole reign of Marcus Aurelius

Artificial Atrial and Ventricular Pacing in the Treatment of Arrhythmias

Abstract: Five patients with various types of arrhythmias refractory to standard therapeutic agents are presented, and the therapeutic approach to the control of these arrhythmias is outlined. The p...

Right Atrial Stimulation in the Treatment of Atrial Flutter

Abstract: The use of right atrial stimulation in the treatment of atrial flutter was evaluated in 10 patients. Atrial flutter was present in these patients from 6 to 96 hr before the procedure. Eigh...

Excavations at the Saxon Monastic Sites of Wearmouth and Jarrow, co. Durham: an Interim Report

Abstract: (1969). Excavations at the Saxon Monastic Sites of Wearmouth and Jarrow, co. Durham: an Interim Report. Medieval Archaeology: Vol. 13, No. 1, pp. 21-66.

Spin orientation during acrylic fiber formation by wet‐spinning

Abstract: The molecular orientation acquired during fiber formation of acrylic fibers by wetspinning has been studied. Orientation was detected by measurements of sonic modulus which were converted into an orientation factor. The orientation correlates very well with the ratio of take-up velocity to the freely extreuded velocity. Several mechanisms for the origin of spin orientation are discussed.

Relation between melting behavior and physical structure in polymers

Abstract: The phenomenon of double melting, as manifested by two characteristic endotherms in the melting region on a differential thermal analysis (DTA) scan, has been studied in nylon 66 and polystyrene as a function of sample treatment by annealing or drawing A variety of techniques were used in these studies including DTA, x-ray diffraction, electron microscopy, and mechanical testing It is shown that the two endotherms are not caused by a bimodal crystal size distribution, by recrystallization, by orientation changes, or by phase changes It is proposed that one endotherm is caused by the melting of foldedchain crystals, while the other is due to the melting of less perfect bundle crystals This view is well supported by the results, especially by the DTA measurements made at different heating rates Published data on the thermal behavior of annealed and drawn poly(ethylene terephthalate) and on polyethylene crystallized at various pressures may also be explained on this basis if it is allowed that in polyethylene the chains may be more extended

Pollen diagrams from the north york moors

Abstract: Summary Four pollen diagrams from the Egton High Moor watershed of the North York Moors are described. Two are from infilled sub-glacial meltwater channels and two from blanket peat. The channel mires developed from woodland through fen peats (dominated by Thelypteris) to acidic bogs during Post-glacial times. The uplands started to accumulate peats in late zone VI or early zone VIIa. The stratigraphy suggests that fire as well as paludification was involved in the inception of blanket peat. Clearance phenomena are observed in pre-Ulmus decline times and some of these are tentatively assigned to Mesolithic activity. In the upper portions of the diagrams massive forest clearance is seen and this is probably due to Bronze Age occupation. The representation of Tilia is discussed in its regional context and the possible significance of the Fagus percentages in the light of Tauber's work is briefly mentioned.

Flow Orientation of Short Fiber Composites

Abstract: A method for characterizing the orientation of short fibers during flow of short fiber composites is described. A system comprised of approximately 50% by volume glass fibers in an epoxy resin matrix was used for this study. A glass rheometer was used to observe steel tracer fibers, which were incorporated into feed particles with the glass. By reacting the epoxy resin with a secondary amine, a product was obtained which did not react further during the measurements. The product also had a viscosity at room temperature similar to com mercial systems at processing temperatures; this made flow measure ments at room temperature possible. A technique of data reduction for the orientation measurements is described.Early results show that, at these high fiber loadings, plug flow with little change in orientation occurs above and below the constriction in the rheometer tube. At the constriction, particles are sheared into strands. If feed particles containing pre-oriented fibers are not used, a "log jam" results...

A phase-shift analysis of electron-helium scattering: I - Elastic scattering below the 2S resonance

Abstract: A phase-shift analysis of electron-helium elastic scattering in the energy range 31 to 191 ev has been made. s- and p-wave phase shifts consistent with the dispersion relation and with experimental information on the total elastic scattering cross section, the diffusion cross section and recent measurements of the differential cross section, to within 5% are obtained. The Gibson-Dolder measurements of the differential scattering cross section are shown to be theoretically preferable to the earlier measurements of Ramsauer and Kollath. The d-wave phase shift cannot be determined to better than 25% by available experimental information. The phase shifts obtained are consistent with, but do not distinguish between, recent non-adiabatic theoretical calculations, but exclude the simple polarized orbital model. They satisfy Spruch bounds based on the experimental polarizability and yield a scattering length of 11a0 in agreement with other determinations.

Some Problems of Punctuation in the Latin Hexameter

Abstract: IN a discussion of the reading in Lucan i. 231, Richard Bentley dismissed Grotius's suggestion Ariminon: ignes on the correct grounds that, like Virgil, Lucan avoids starting a new sentence or clause at the beginning of the sixth foot of the hexameter, except with a pair of monosyllables (as in 6. 700, per quam) or with a word emphasized either by repetition (as in 7. 350, ipsi … ipsi) or by a strong contrast (as in Cicero, Arat. 266, hic totus medius circo disiungitur: ille… —the only example of this sort of break in Cicero's poetical fragments).

Free and membrane bound ribosomes of the cotyledons of Vicia faba (L.) : I. Seed development.

Abstract: Changes in the quantities of free and membrane-bound ribosomes were followed in the cotyledons of developing seeds During the phase of storage protein synthesis, free and membrane bound ribosomes do not interchange, and as both classes synthesise protein in vivo, it is possible that they may synthesise different groups of proteins This suggestion is discussed in relationship to the developing cotyledon

Differential Criminalization under Operation Streamline: Challenges to Freedom of Movement and Humanitarian Aid Provision in the Mexico-US Borderlands

Abstract: On January 14, 2008, under the wider program of the Arizona Denial Prosecution Initiative, Operation Streamline was put into effect in the Tucson Sector of the Mexico-US borderlands. Initially implemented in Del Rio, Texas, this program—aimed at mass incarceration of undocumented persons to reduce repeated migration attempts—has been most rigorously applied in the Tucson Sector, known as both the busiest and deadliest corridor for migration. Every day approximately seventy migrants are apprehended by the US Border Patrol and then sentenced for up to 180 days imprisonment. I consider Operation Streamline and its impacts on undocumented migrants through the lens of local organizing, particularly by the humanitarian aid group No More Deaths, asserting that such policies—which further militarize the border and justify criminalization of migrants in the public eye—put bodies at greater risk, even before they are prosecuted, through practices of spatial containment that add to the rigours of crossing the Sonoran Desert. In this work I explore the methods in which grassroots humanitarian aid groups apply practices of direct action to challenge such policies and promote freedom of movement.

The elastic constants and interatomic binding in yttria-stabilised zirconia

Abstract: Zirconia (ZrO2) can be forced into a cubic fluorite structure by the addition of more than 7 mol % yttria (Y2O3). The elastic stiffness constants of cubic zirconia single crystals containing 8 and 12 mol % yttria have been determined between 77 and 300° K by an ultrasonic pulse echo technique. Elastic constants are almost temperature-independent and at 77° K are for the 8 and 12 mol % respectively: C 11=2.04, C 12=0.87, C 44=1.58; C 11=2.23, C 12=0.973, C 44=1.54 (units: 1012 dynes cm−2). Compressibilities and elastic compliances are also presented. The data provide a basis for discussion of crystalline stability and the nature of the interatomic forces. The decreasing cubic lattice stability as the yttria content is reduced is demonstrated quantitatively. An ionic model closely characterises the binding forces. The repulsive energy is about 12% of the Madelung attractive energy. Debye temperatures calculated from the elastic constant data extrapolated to 0° K are 595 and 604° K for the 8 and 12 mol % respectively.

Non empirical LCAO-MO-SCF calculations with gaussian type functions on some three membered ring heterocycles

Abstract: Non empirical molecular quantum chemical calculations have been performed on the three membered ring heterocyclic molecules, aziridine, oxirane and thiirane and the as yet unknown 1 azirene, 2 azirene, oxirene and thiirene. For the nitrogen compounds the corresponding protonated species have been investigated and for comparison the isoelectronic saturated and unsaturated hydrocarbon molecules, cyclopropane and cyclopropene. A discussion is given of total energies, eigenvalues, and gross atomic populations.

The subunit structure of jack-bean urease.

Abstract: 1. Urease of specific activity 160-180 Sumner units/g. (Sumner, 1951) was purified from jack-bean meal. The preparation was pure on the basis of polyacryl-amide-gel electrophoresis and N-terminal studies. 2. By using both the 1-fluoro-2,4-dinitrobenzene method and the phenyl isothiocyanate method a single N-terminal methionine residue was found. 3. A single C-terminal sequence -Tyr-Leu-Phe was found by studies with carboxypeptidase A, carboxypeptidase B and hydrazinolysis. 4. N-Bromosuccinimide cleavage showed that five unique tryptophan sequences were present: Trp-Ala, Trp-Glu, Trp-Gly, Trp-Met and Trp-Arg. 5. Polyacrylamide-gel electrophoresis in sodium dodecyl sulphate showed that urease had a subunit molecular weight of 76000. 6. The yield of N- and C-terminal amino acids, the number of tryptic peptides and tryptophan sequences and the above polyacrylamide-gel electrophoretic measurement all suggest that urease contains a single structural subunit of molecular weight 75000.

Free and membrane-bound ribosomes of the cotyledons of Vicia faba (L.)

Abstract: During the first few days of germination, the RNA content of the cotyledons remained approximately constant, but the quantity of membrane-bound ribosomes increased. Experiments with orthophosphate-32P indicated that these ribosomes were synthesised de novo, and did not originate by the attachment to membranes of pre-existing free ribosomes. This conclusion was discussed in relation to the suggestion that free and membrane-bound ribosomes synthesise different groups of proteins.

An Ecological Study on Laminaria Ochroleuca

Abstract: The distribution of Laminaria ochroleuca along the south-west coast of England and the Isles of Stilly is brought up to date. The pattern of distribution is discussed with reference to certain factors controlling the ‘ performance’ and success of the species on the northernmost edge of its range. The performance of individuals of the species (measured as net stipe production) sampled from populations growing on the coast of south-west England is compared with populations from north-west Spain, where it is growing in the centre of its geographical range. The degree of exposure to direct onshore wave action appears to govern the upper limit of its bathymetric range as well as its distribution along the south-west coast of England. It was found possible to age this species using the method and precautions described by Kain for Laminaria hyperborea . The stipe material sampled from the English populations had a higher ash content per gram dry weight and a higher calorific content per gram of organic material than that from the Spanish populations. Individuals from the English population had a lower weight per unit length of stipe in all age-classes than those from Spain. It is suggested that incident radiation may be a more important factor than temperature in controlling the northward limit of the species.

New high‐temperature polymers. VIII. Ordered benzoxazole‐ and benzothiazole‐imide copolymers

Abstract: Ordered heterocycle copolymers of high thermal stability were prepared from aromatic dianhydrides reacted with aromatic diamines containing preformed benzoxazole or benzothiazole units. These ordered benzoxazole-imide and benzothiazole-imide copolymers were prepared in the form of their soluble precursor polyamic-acids, which, after fabrication to desired shapes, were converted to the thermally stable polymer. In general, these polymers are more resistant to air oxidation at elevated temperatures than are simple aromatic polyimides, and their thermooxidative stability is equal to or greater than that reported for benzoxazole or benzothiazole homopolymers. Unlike the o-hydroxyamide precursors to simple polybenzoxazoles, the amic acid precursors to benzoxazole-imide ordered copolymers do not require temperatures above 300°C to complete ring closure nor inert atmospheres to prevent polymer degradation during ring formation. Excellent self-supporting films and film coatings for metals were prepared. Selected compositions were readily spun to excellent fiber.