Showing papers by "Durham University published in 1977"

Simple Monte Carlo Tests for Spatial Pattern

Abstract: The Monte Carlo approach to testing a simple null hypothesis is reviewed briefly and several examples of its application to problems involving spatial distributions are presented. These include spatial point pattern, pattern similarity, space‐time interaction and scales of pattern. The aim is not to present specific “recommended tests” but rather to illustrate the value of the general approach, particularly at a preliminary stage of analysis.

Eye movement strategies involved in face perception.

Abstract: Recordings were made of the eye fixations of three subjects in two tasks involving black-and-white photographs of faces. In the first task, subjects matched a test face with a previously viewed target face; in the second task, subjects compared two simultaneously presented faces. The eye movements were recorded with a corneal reflection technique. Each subject showed an individual fixation strategy for the tasks; in particular each subject had one or more preferred facial feautres which were viewed foveally in both tasks. The subjects also showed some tendency to use a regular sequential pattern of eye movements. However, the sequences used differed from one task to the other. Although some aspects of the results support the scanpath hypothesis of Noton, it is suggested that an alternative interpretation is possible.

Factors affecting the age of first breeding of the kittiwake rissa tridactyla

Abstract: SUMMARY At a Kittiwake colony in Northumberland, 80% of those birds which returned to their natal colony to breed were males and these supplied 52% of all male recruits. More females breed away from their natal colony than males. There was no differences in the proportions of young fledged from sites in the centre or at the edge of the colony, or by parents of different experience, which returned to breed. Kittiwakes breed for the first time at ages from 3 to 8 years, but most at 4 or S years old. Males arrive back at the colony at an earlier age than females and breed for the first time one year earlier. Males obtaining sites at the centre of the colony first breed at an earlier age than those at the edges. Neither the age nor the area of first breeding appear to be transmitted from parent to offspring. Males breeding first aged 4 years or younger produced more young than those which first bred aged 5 years or older, despite their partners laying smaller clutches. This difference was most marked among those males recruited to sites in the centre of the colony. The advantage of this earlier breeding is counteracted by a lower survival rate among those males which start to breed at the younger ages. In all breeding Kittiwakes, annual reproductive output increases with experience while annual survival rates decrease. Once they had started to breed, many birds failed to breed in one subsequent season. Nearly 60% of these cases of intermittent breeding occurred in the year following first breeding. Intermittent breeding was most frequent among young birds and among females. It is suggested that each breeding involves a cost to the individual in terms of reduced survival, and that deferred and intermittent breeding are means of guarding survival. A model is proposed whereby the age at which a bird starts to breed, the nesting site which it obtains, and its subsequent breeding strategy result in each individual producing an optimal number of reproducing offspring in its lifetime, relative to its quality.

The effects of sand movement on intertidal seaweeds and selected invertebrates at Bound Rock, New Hampshire, USA

Abstract: A seasonal study of sand movement and the benthic intertidal organisms at Bound Rock, New Hampshire, USA was conducted between November, 1973 and February, 1975. The site is subjected to irregular sand fluctuations, as well as diurnal, neapspring and major summer sand intrusions. The abundance and distribution of intertidal species was interrelated with the historical sand fluctuations at the area. For example, the lower limits of Mytilus edulis, Balanus balanoides and Porphyra umbilicalis approximated the highest summer sand elevations. Highly abraded rock surfaces in the lower intertidal zone were dominated by opportunistic annuals (e.g. Enteromorpha spp.) and perennial psammophytic or sand-loving seaweeds (e.g. Ahnfeltia plicata and Sphacelaria radicans). Overall, the intertidal seaweed populations at Bound Rock showed a lower number of perennials and fewer species than adjacent rocky shores. The low species diversity of seaweeds at the study site is attributable to unstable environmental conditions and a limited number of habitats. Even so, several psammophytic microhabitats are evident at Bound Rock depending upon the extent of sand burial and abrasion. The morphological and reproductive adaptations of several psammophytic species are discussed.

Application of ESCA to polymer chemistry. XVI. Electron mean free paths as a function of kinetic energy in polymeric films determined by means of ESCA

Abstract: Electron mean free paths as a function of kinetic energy have been measured by the substrate overlayer technique for in situ-polymerized films of poly(p-xylylene) and the monochloro- and monobromo-substituted derivatives. The results are compared with previous estimates of mean free paths available in the literature for organic materials. Comparison is also drawn with corresponding experimental data for typical metals and semiconductors, and it is shown that organic polymers fit into a consistent picture which may be rationalized on the basis of existing theory. For electrons of kinetic energy ∼969 eV, ∼1170 eV, 1202 eV, and 1403 eV, mean free paths of ∼14 A, ∼22 A, ∼23 A, and ∼29 A, respectively, are obtained for the poly(p-xylylene) polymer films studied in this work.

World-wide variations in the direction and concentration of cirque and glacier aspects

Abstract: Topoclimatic effects on glacier balance encourage shade, lee and east-facing glaciers in vary- ing combination in different regional climates and at different altitudes. Present-day glaciers usually face slightly east of poleward on average: in Scandinavia and the Urals, consistent westerly winds strengthen the lee tendency, especially where gentle summits favour drifting of snow. Eastward cirque aspects are found in the Falkland Islands, New Hampshire and Central Spain, east-northeast aspects in the American Rockies, the Faeroes, Central Europe, Japan and Tasmania. In Scandinavia, the British Isles and the Carpathians, northeastward resultants are most common, showing a lee effect tempered with a shade effect. Elsewhere (in the Canadian Arctic, Alaska, British Columbia, western U.S.A., central Chile, the Alps, southwest and central Asia, the Altai and even Papua-New Guinea), both cirque and glacier aspect resultants are poleward or within 30? further east. This situation reflects dif- ferential ablation from direct solar radiation as a more important factor than wind. Cirque aspects provide a constraint on palaeoclimatic reconstructions but can- not provide precise information on palaeowind direc- tions. The degree of asymmetry (vector strength) varies more locally and is usually greater in ranges which were only just high enough to nourish glaciers. For a temporal comparison of glaciers with cirques, this observation may be formalised as a "law of decreasing glacial asymmetry with increasing glacier cover".

ESCA applied to polymers. XV. RF Glow-discharge modification of polymers, studied by means of ESCA in terms of a direct and radiative energy-transfer model†

Abstract: The crosslinking of an ethylene–;tetrafluoroethylene copolymer by exposure to an argon plasma, excited by an inductively coupled RF field, is studied over a wide range of pressures and power loadings. The results are interpreted in terms of a two-component, direct and radiative energy-transfer model showing that the outermost monolayer crosslinks rapidly via direct energy transfer from argon ions and metastables.

Perks, pilferage, and the fiddle: The historical structure of invisible wages

Abstract: History lives on. The perpetual and perpetuating myth of the present is to believe that we -are liberated from the anguish of the past. On the contrary, the greatest source of history is impregnated in the mundane and everyday world of the present. The meaning of the world of work, for example, is revealed in its relationship to its past. Workers are not only, on the whole, paid as a class,1 those situated at structurally disadvantaged parts receive large segments of their wages “invisibly” - as tips or fiddles from customers, or pilferage and perks from employers. The crucial common factor in these forms of “invisible wages” is the added power which accrues to employers through their establishment. They are meaningfully located, however, not simply as archaic relics in the gradual rational liberation of the present from the feudal bond, but as forms of domination crucial to the persistence and growth of modern capitalism because of their solution to those disciplinary problems not soluble in money alone.

The macrophytic vegetation of the River Tees in 1975: observed and predicted changes

Abstract: SUMMARY. An account is given of the distribution of macrophytes in the River Tees and its tributaries, north-east England, together with a critical discussion of the problems involved in recording data in a form which can be used for monitoring long-term changes of vegetation in rivers. Among the conventions and methods adopted in the present study are an attempt to define the vertical limits of the river sensu strictu as opposed to the bank, the extension of the term macrophyte to include as many visually obvious photosynthetic organisms as possible, the use of a check-list prepared in advance which contains a wider range of species than are actually expected for the river, and the collection of two different types of standard record for each 0.5 km length of river. The Tees has been the subject of intermittent observations on its vegetation for some 45 years. The most obvious change has taken place since 1965, with a substantial upstream spread of four submerged angiosperm species. Potamogeton crispus, Zannichellia palustris and Myriophyllum spicatum were previously present only in the lower reaches of the Tees, and have spread 25, 9.5 and 4.5 km respectively upstream from their previously known most upstream localities. Ranunculus penicillatus var. calcareus is an apparent invader to the river. It seems probable that these changes have taken place since 1971 as a result of regulation of the Tees by Cow Green Reservoir. Further changes are predicted with the advent of water transfer from the Tyne to Tees around 1980, because at least twenty-six macrophytes are known to be present in the former river that are either absent or confined to the lowest stretches of the latter.

Influence of zinc on lotic plants

Abstract: SUMMARY. Field and laboratory studies have been carried out on the tolerance to zinc of the filamentous green algae Hormidium rivulare Kutz., H. flaccidum Kutz. and H. fluitans (Gay) Heering growing in flowing waters. Forty-seven different sites in England, France, Germany and Ireland were included, the majority of them chosen to represent examples of zinc pollution resulting from past or present mining activities. All three species were widespread both in waters free of zinc pollution and waters with zinc pollution, and H. rivulare and H. flaccidum were frequent at a site with the highest zinc level included in the survey (mean of 22.8 mg l−1, maximum of 30.2 mg l−1 Zn passing through a filter). At sites with higher zinc levels, populations showed increased resistance to zinc of the filamentous green algae Hormidium rivulare Kutz., H. flaccidum creased resistance being largely, if not entirely, the result of genetic adaptation. An increased frequency of geniculations can occur both as an environmental and a genetic response to very high zinc levels. The application of various statistical analyses to the data suggests that two groups of chemical factors may be influencing the toxicity of zinc in the field. The first group which appears to increase the toxicity of zinc includes cadmium and lead, while the second group, which decreases the toxicity of zinc, includes magnesium, calcium and various hardness factors. As the occurrence of zinc, cadmium and lead in the field are all strongly intercorrelated, it is not possible to distinguish clearly the effects of one from the other, although the data do suggest that cadmium is more likely than lead to influence zinc toxicity. The ‘amelioration’ factors are also strongly intercorrelated in the field, so it is difficult to comment on their relative importance. There is some indication for H. rivulare at least, that an increase in PO4-P and a decrease in pH may also reduce zinc toxicity.

Filter elements for gas or liquid and methods of making such elements

Abstract: A filter element for gas or liquid comprises a layer of glass, ceramic, metal, mineral wool or organic fibers containing, wholly within the layer, an apertured sheet, for example of steel or aluminum, the fibers being bound to one another throughout the layer and through the apertures, as well as to the sheet itself, by a synthetic resin such as silicone resin or polyurethane. The filter element is formed by mounting the apertured sheet a selected distance above a filter surface on which the fibers build up while a slurry containing the fibers is drained through the filter surface. When the fibers have built up to a predetermined distance above the sheet, the fibers containing the sheet are removed and the assembly impregnated with a synthetic resin and cured. Two or more grades of slurry mixture may be used in succession to produce a density grading through the thickness of the fibrous layer. In the case of cylindrical elements, end caps are fitted and made fluid tight by a synthetic resin, a taper fit or a gasket.

Status of Large Gulls Nesting on Buildings

Abstract: Some 3,000 pairs of Herring Gulls are now known to be nesting on buildings, mainly in coastal towns they are increasing most rapidly in eastern Britain, where recruitment is taking place from natural colonies. A smaller number of Lesser Black-backed Gulls has occupied rooftops in the Bristol Channel region.

Diving injuries to the inner ear.

Abstract: Most of the previous literature concerning otologic problems in compressed gas environments has emphasized middle ear barotrauma. With recent increases in commercial, military, and sport diving to ...

Nitrogen fixation by blue-green algal communities in the intertidal zone of the lagoon of Aldabra Atoll.

Abstract: All eight types of blue-green algal community sampled from the intertidal sediments of the lagoon of Aldabra showed detectable rates of acetylene reduction, and six of them showed at least some examples of rates considered by previous authors to be rapid. When the reduction rates are related to the chlorophyll a contents of the communities, the maximum rates recorded come in the following order: Hyella balani, Scytonema sp., Hyella balani-Schizothrix sp., Calothrix crustacea, Rivularia sp., Microcoleus chthonoplastes, Hyella balani-purple sulphur bacteria, Pleurocapsa-Chroococcus. With the exception of the mixed Hyella balani-purple sulphur bacterial community, the rate of acetylene reduction was in all experiments greater in the light than in the dark, the difference being significant (P<0.05) in the majority of cases. The rates were similar in all experiments whether incubation was carried out with sea or brackish water. It seems probable that nitrogen fixation by blue-green algal communities makes an important addition to the lagoon ecosystem, and that not only heterocystous, but also some non-heterocystous, species are involved. Among the latter, the data for Hyella balani and Microcoleus chthonoplastes are especially convincing.

Filters for liquids or gases

Abstract: Filter elements are described in which a pleated cylindrical sheet of non-woven microporous glass fibre filter material impregnated with a binder, which may be silicone, polyurethane, phenolic resin or epoxy resin, is mounted in contact with a cylindrical supporting sheet of, for example, expanded metal for maintaining the filter material against shock pressure loads. To protect the filter material during assembly a porous layer of protective material may be interposed between the filter material and the supporting cylinder. The supporting cylinder may be a simple cylinder or pleated so as to fit the filter material. An activated carbon layer for removing odors during air filtration may be added to the filter material. When the air contains oil mist, a layer containing dye that will be taken up by the oil and discolor the filter element as a warning indication that the filter has become saturated, may be interposed between the filter material and the activated carbon layer. The filter material may comprise an organic binder holding together borosilicate glass fibres, this amorphous mass being further impregnated by a synthetic resin binder. The filter material may consist of a glass fibre filter paper with a further layer of non-woven material secured thereto by a synthetic resin binder.