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Showing papers by "Dalhousie University published in 1984"


Journal ArticleDOI
TL;DR: This article showed that infants can discriminate non-native speech contrasts without relevant experience, and that there is a decline in this ability during ontogeny, which is a function of specific language experience.
Abstract: Previous work in which we compared English infants, English adults, and Hindi adults on their ability to discriminate two pairs of Hindi (non-English) speech contrasts has indicated that infants discriminate speech sounds according to phonetic category without prior specific language experience (Werker, Gilbert, Humphrey, & Tees, 1981), whereas adults and children as young as age 4 (Werker & Tees, in press), may lose this ability as a function of age and or linguistic experience. The present work was designed to (a) determine the generalizability of such a decline by comparing adult English, adult Salish, and English infant subjects on their perception of a new non-English (Salish) speech contrast, and (b) delineate the time course of the developmental decline in this ability. The results of these experiments replicate our original findings by showing that infants can discriminate non-native speech contrasts without relevant experience, and that there is a decline in this ability during ontogeny. Furthermore, data from both cross-sectional and longitudinal studies shows that this decline occurs within the first year of life, and that it is a function of specific language experience. © 2002 Published by Elsevier Science Inc.

2,438 citations


Journal ArticleDOI
TL;DR: The cortical representations of the hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2–8 months after surgical amputation of digit 3, or of both digits 2 and 3.
Abstract: The cortical representations ofthe hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2-8 months after surgical amputation of digit 3, or of both digits 2 and 3. Digital nerves were tied to prevent their regeneration within the amputation stump. Suc­ cessive maps were derived in several monkeys to determine the nature of changes in map organization in the same individuals over time. In all monkeys studied, the representations of adjacent digits and pal­ mar surfaces expanded topographically to occupy most or all of the cortical territories formerly representing the amputated digit(s). With the expansion of the representations of these surrounding skin surfaces (1) there were severalfold increases in their magnification and (2) roughly corresponding decreases in receptive field areas. Thus, with increases in magnification, surrounding skin surfaces were represented in correspondingly finer grain, implying that the rule relating receptive field overlap to separation in distance across the cortex (see Sur et aI., '80) was dynamically maintained as receptive fields progressively decreased in size. These studies also revealed that: (1) the discontinuities between the representations of the digits underwent significant translocations (usually by hundreds of microns) after amputation, and sharp new discontinuous boundaries formed where usually separated, expanded digital representa­ tions (e.g., of digits 1 and 4) approached each other in the reorganizing map, implying that these map discontinuities are normally dynamically main­ tained. (2) Changes in receptive field sizes with expansion of representations of surrounding skin surfaces into the deprived cortical zone had a spatial distribution and time course similar to changes in sensory acuity on the stumps of human amputees. This suggests that experience-dependent map changes result in changes in sensory capabilities. (3) The major topographic changes were limited to a cortical zone 500-700 JIm on either side of the initial boundaries of the representation of the amputated digits. More dis­ tant regions did not appear to reorganize (i.e., were not occupied by inputs from surrounding skin surfaces) even many months after amputation. (4) The representations of some skin surfaces moved in entirety to locations within the former territories of representation of amputated digits in every

1,327 citations


Journal ArticleDOI
TL;DR: It would be misleading to claim that all relevant experimental results directly corroborate the evolutionary theory of senescence, but there are two corollaries which follow from the general theory itself: the reproductive schedule of an outbred population will give rise to natural selection acting to accelerate senescences in populations with a relatively earlier age of reproduction and postpone senescenced populations.
Abstract: Evolutionary genetics seems to have found the fundamental cause of senescence: the decline in the sensitivity of natural selection to gene effects expressed at later ages in most populations of organisms with separate somatic and germline tissue. (Here "senescence" refers to decline in age-specific fitness-components after the onset of reproductive maturity.) This idea traces back to Haldane (1941) and Medawar (1946, 1952), with considerable elaboration and elucidation since then (Williams, 1957; Hamilton, 1966; Edney and Gill, 1968; Emlen, 1970; Charlesworth and Williamson, 1975; Charlesworth, 1980; Rose, 1983a). While there are still clear limitations to the mathematical formulation of this theory (cf. Hamilton, 1966; Charlesworth, 1980), the basic formal analysis leads to a straightforward conclusion: the first partial derivative of fitness with respect to appropriately scaled changes in age-specific life-history characters usually declines in magnitude with the age of these changes. The force of natural selection thus declines with age. This overall theory and its particular subsidiary variants lead to a number of empirically testable corollaries (Rose, 1983a, 1983b). Some of these corollaries are specific to the subsidiary variants of the theory (Rose and Charlesworth, 1980, 1981a, 1981b; Rose, 1983b), sothattests of them individually do not test the theory as a whole. Fortunately, there are two corollaries which follow from the general theory itself: the reproductive schedule of an outbred population will give rise to natural selection acting to (i) accelerate senescence in populations with a relatively earlier age of reproduction and (ii) postpone senescence in populations with a relatively later age of reproduction (Edney and Gill, 1968; Rose, 1983a). The former prediction has been corroborated by Sokal (1970) using Tribolium castaneum, while the latter has been corroborated by Wattiaux (1968a, 1968b) and by Rose and Charlesworth (1980, 198 lb), using Drosophila species. Once a theory has been well-developed mathematically and then empirically corroborated, attention turns to experiments in which the theory either is not clearly corroborated or is ostensibly refuted. It would be misleading to claim that all relevant experimental results directly corroborate the evolutionary theory of senescence. Sokal (1 970) and Mertz (1975) using Tribolium castaneum and Taylor and Condra (1980) using Drosophila pseudoobscura found heterogeneity between lines in experiments with replication, such that some lines did not exhibit the predicted response to the imposed selective regime. Taylor and Condra (1980) also found a difference in the response of the sexes which was later attributed to the pattern of female mating preference (Taylor et al., 1981). More problematic still are the studies from the Lints laboratory, one of which failed to obtain a direct response to artificial selection for longevity (Lints et al., 1979), while another gave puzzling fluctuations in life-history attributes (Lints and Hoste, 1974, 1977). Lints (1978, 1983) has made a great deal of these problems, contending that they cast doubt on all proposed evolutionary theories of senescence. While it can be argued that these puzzling results are due to technical artifacts such as inbreeding, genetic disequilibrium, and inadequate controls (cf. Rose and Charlesworth, 1981b), the only ef-

733 citations


Journal ArticleDOI
TL;DR: The method described here provides a powerful and generally applicable molecular taxonomic approach towards a global phylogeny encompassing all organisms and organelles.
Abstract: To probe the earliest evolutionary events attending the origin of the five known genome types (archaebacterial, eubacterial, nuclear, mitochondrial and plastid), we have analyzed sequences corresponding to a ubiquitous, highly conserved core of secondary structure in small subunit rRNA. Our results support (i) the existence of three primary lineages (archaebacterial, eubacterial, and nuclear), (ii) a specific eubacterial ancestry for plastids and mitochondria (plant, animal, fungal), and (iii) an endosymbiotic, evolutionary origin of the two types of organelle from within distinct groups of eubacteria (blue-green algae (cyanobacteria) in the case of plastids, nonphotosynthetic aerobic bacteria in the case of mitochondria). In addition, our analysis suggests (iv) a biphyletic origin of mitochondria, with animal and fungal mitochondria branching together but separately from plant mitochondria, and (v) a monophyletic origin of plastids. The method described here provides a powerful and generally applicable molecular taxonomic approach towards a global phylogeny encompassing all organisms and organelles.

372 citations


Journal ArticleDOI
TL;DR: It is concluded that the palatability of highly concentrated salt solutions increases in sodium-deplete rats because of a shift in FAPs, which may be instrumental in directing the appetitive behavior of the animal.
Abstract: Sterotyped fixed action patterns (FAPs) are elicited in rats by oral infusions of taste solutions. These taste-elicited FAPs can be classified as either ingestive or aversive. They reflect the palatability of the taste and can be modified by learning and by the physiological state of the animal. These studies demonstrated that when the physiological state of the rat is altered by sodium depletion, the pattern of FAPs elicited by oral infusions of 0.5 M NaCl shifts from a mixture of ingestive and aversive components (while sodium replete) to exclusively ingestive ones (while sodium deplete). This shift in taste reactivity occurred the first time the rats were made sodium deplete. A similar shift was not observed to accompany infusions of 0.01 M HCl, a taste solution that also elicited mixed ingestive and aversive FAPs. This result suggests that the shift in response to NaCl is not due to a general change in ingestive bias or to a general taste deficit. On the basis of the change in FAPs, it is concluded that the palatability of highly concentrated salt solutions increases in sodium-deplete rats. Such a shift in salt palatability may be instrumental in directing the appetitive behavior of the animal.

211 citations


Journal ArticleDOI
TL;DR: In this article, rare earth element concentrations have been measured in organic-rich Luce river water and coastal sea water and they have been associated with Feorganic matter colloids which flocculate during estuarine mixing.

209 citations


Journal ArticleDOI
TL;DR: A mass mortality of Strongylocentrotus droebachiensis, attributed to disease, was monitored in an echinoiddominated barren ground at Eagle Head on the south-western coast of Nova Scotia, Canada, in 1982 and time to morbidity was not affected significantly by nutritional condition and was similar for juvenile and adult echinoids.
Abstract: A mass mortality of Strongylocentrotus droebachiensis, attributed to disease, was monitored in an echinoiddominated barren ground at Eagle Head on the south-western coast of Nova Scotia, Canada, in 1982. Mortality was 70% in a shallow (3 m) nearshore area, resulting in a loss of echinoid biomass of 2 042 g fresh weight m-2, and 6% in deeper (7 m, 10 m) offshore areas. Echinoid density, size and nutritional condition (gonad index) were highest in the nearshore area. Survivorship was higher in juveniles (<15 mm diameter) than in adults resulting in the formation of a bimodal size distribution in the nearshore area. Mortality began around early October, near the peak of the annual cycle of seawater temperature (∼15°C), and was arrested by early December (seawater temperature ∼7°C) when morbid echinoids appeared to recover. In laboratory experiments, time to morbidity of S. droebachiensis exposed to morbid conspecifics increased exponentially with decreasing temperature (20° to 8°C). There was no survival at 20° and 16°C, 20% survival at 12°C and 100% survival at 8°C after 60 d; suggesting a lower temperature limit (between 12° and 8°C) for possible transmission of a pathogenic agent. Morbid laboratory echinoids from experiments at 16°C, and recovering echinoids collected in the nearshore area in early December, showed 100 and 85% survival respectively at <=8°C, and 0 and 15% survival respectively at 16°C, after 30 d. Time to morbidity was not affected significantly by nutritional condition and was similar for juvenile and adult echinoids. Time to morbidity was greater in echinoids exposed to one or three morbid individuals continuously, or seven morbid individuals for 1 h, relative to higher levels of exposure (up to seven morbid individuals continuously). Recent mass mortalities in S. droebachiensis have occurred in years of record high sea surface temperatures. The extent of mortality is correlated with the magnitude and duration of temperatures above a lower limit.

190 citations


Journal ArticleDOI
TL;DR: The aqueous solubilities of phenanthrene, anthracene, 2-methylanthracene and benzo(a)pyrene were determined at temperatures ranging from 3.7 to 25.3°C and salinities ranging from 0 to 36.7°C as mentioned in this paper.

182 citations


Journal ArticleDOI
TL;DR: In this article, the concept of effective sample size is discussed, and various methods of estimating this quantity are examined; it is found that "effective sample size" is quite difficult to estimate reliably, however, a procedure is described which they feel could be used successfully; it was noted that the concept could be extended to spatial arrays of data, in some circumstances.
Abstract: Statistical and dynamical relationships between observed values of a geophysical system or model effectively reduce the number of independent data. This reduction is expressible in terms of the covariance structure of the process and, in some instances, it is reasonable to devise a measure of the “effective sample size” in terms of sample statistics. Here we discuss the concept of “effective sample size,” and, having settled upon one of several possible definitions, examine various methods of estimating this quantity. It is found that “effective sample size” is quite difficult to estimate reliably. However, a procedure is described which we feel could be used successfully; it is noted that the concept could be extended to spatial arrays of data, in some circumstances.

169 citations


Journal ArticleDOI
06 Sep 1984-Nature
TL;DR: In this paper, it was shown that the vertical mixing induced by turbulence in the upper mixing layer of the ocean transports algae through a light field that decreases exponentially from the sea surface.
Abstract: In their natural environment, algal cells may experience large amplitude variations in incident light on time scales shorter than those associated with the reproductive rate. A major source of variability is due to vertical mixing of water masses: turbulence in the upper mixing layer of the ocean transports algae through a light field that decreases exponentially from the sea surface. Several attempts have been made to discover how the physiological adaptation of algae to fluctuating light1–9 might affect the magnitude of marine primary production10–16,17, but it has proved difficult to estimate the vertical mixing rate at sea, and hence the time scales of irradiance variability 18,19. We recently succeeded, for the first time to our knowledge, in making direct measurement of rates of turbulent kinetic energy (TKE) dissipation, simultaneously with those of photoadaptation properties of natural phytoplankton populations. Dissipation of TKE in these experiments was a strong determinant of algal photosynthetic rate in the upper mixing layer; we conclude that the vertical mixing induced by turbulence to a large degree controls the photosynthetic performance of algae in nature.

168 citations


Journal ArticleDOI
TL;DR: In this article, the metals, Cd, Pb, Cu, Zn, Mn and Fe were sequentially extracted from the dust into five fractions, exchangeable metal, carbonate bound metal, MnFe oxide bound metal and the residue.

Journal ArticleDOI
01 Aug 1984-Geology
TL;DR: The Andaman Sea region of the Indian Ocean may provide an actualistic model for the origin of the Troodos complex and other Mideast ophiolite complexes.
Abstract: Any comprehensive model for the origin of the Troodos complex and other Mideast ophiolite complexes must explain the geochemical evidence for subduction-zone involvement, the thin inferred oceanic crust, the extensional environment indicated by sheeted dikes, the existence of fault zones perpendicular to the inferred spreading axes, and the discontinuous nature of ophiolite exposures around the Arabian block. The Andaman Sea region of the Indian Ocean may provide an actualistic model for the origin of these ophiolites. There, spreading takes place in short segments above a subduction zone in the region of active spreading. The Andaman Sea model substantially accounts for the known geologic and geophysical data from the circum-Arabian ophiolite belt, and it leads to some predictions about the structural and geophysical relationships to be expected in this important belt. The model also predicts that Andaman Sea spreading-center magmas may be similar in composition to those found in the Mideast ophiolites.

Journal ArticleDOI
TL;DR: In a southwestern Nova Scotia kelp forest the average density of Laminaria longicruris Pyle remained constant through 1 yr at ≈1.2 plant·m −2 and the rate of mortality among macroscopic individuals of L. digitata (Huds.) Lamour was related to initial plant size and distance to nearest congeneric neighbour.

Journal ArticleDOI
TL;DR: Variations in COII gene structure and size, as well as the presence of repeated COII sequences, illustrate at the DNA sequence level, factors which contribute to higher plant mitochondrial DNA diversity and complexity.
Abstract: We have determined the sequence of the wheat mitochondrial gene for cytochrome oxidase subunit II (COII) and find that its derived protein sequence differs from that of maize at only three amino acid positions. Unexpectedly, all three replacements are non-conservative ones. The wheat COII gene has a highly-conserved intron at the same position as in maize, but the wheat intron is 1.5 times longer because of an insert relative to its maize counterpart. Hybridization analysis of mitochondrial DNA from rye, pea, broad bean and cucumber indicates strong sequence conservation of COII coding sequences among all these higher plants. However, only rye and maize mitochondrial DNA show homology with wheat COII intron sequences and rye alone with intron-insert sequences. We find that a sequence identical to the region of the 5' exon corresponding to the transmembrane domain of the COII protein is present at a second genomic location in wheat mitochondria. These variations in COII gene structure and size, as well as the presence of repeated COII sequences, illustrate at the DNA sequence level, factors which contribute to higher plant mitochondrial DNA diversity and complexity.

Journal ArticleDOI
TL;DR: In this article, the uppermost muddy turbidite unit is mapped throughout the northern half of the fan; its volume, grain-size distribution and the maximum height of deposition on the basin slopes are known.
Abstract: Several Holocene turbidites can be correlated across much of Navy Fan through more than 100 sediment core localities. The uppermost muddy turbidite unit is mapped throughout the northern half of the fan; its volume, grain-size distribution and the maximum height of deposition on the basin slopes are known. These parameters can be related to the precise channel morphology and mesotopography revealed by deep-tow surveys. Thus there is sufficient information to estimate detailed flow characteristics for this turbidity current as it moved from fan valley to distal basin plain. On the upper fan, the gradient and the increasing downstream width of the channel and only limited flow overspill suggest that the flow had a Froude number close to 1.0. The sediment associated with the channel indicates friction velocities of about 0.06 m s−1 and flow velocities of about 0.75 m s−1. Using this flow velocity and channel dimensions, sediment concentration (∼2×10−3) and discharge are estimated, and from a knowledge of the total volume of sediment deposited, the flow duration is estimated to be from 2 to 9 days. It is shown that the estimates of Froude number, drag coefficient, and sediment concentration are not likely to vary by more than a factor of 2. On the mid-fan, the flow was much thicker than the height of the surface relief of the fan and it spread rapidly. The cross-flow slope, determined from the horizontal extent of turbidite sediment, is used to estimate flow velocity, which is confirmed by consideration of both sediment grain size and rate of deposition. This again allows sediment concentration and discharge to be estimated. The requirements of flow continuity, entrainment of water during flow expansion, and observed sediment deposition provide checks on all these estimates, and provide an integrated picture of the evolution of the flow. The flow characteristics of this muddy turbidity current are well constrained compared to those for more sand-rich late Pleistocene and early Holocene turbidity currents on the fan.

Journal ArticleDOI
TL;DR: Perennials are well anchored in the sediment, are more able to withstand removal by ice, and have reserves available for production of new leaves when ice melts, and seed germination was greatest in areas where ice had removed whole plants (or their aboveground parts) than among mature ramets which had survived winter intact.
Abstract: The formation of winter ice, and its movement with the tides, has had a major influence on the life-history parameters of shallow-water populations of the rhizomatous marine angiosperm eelgrass (Zostera marina) in Nova Scotia, Canada. In this region, and annual form of eelgrass inhabits intertidal and shallow subtidal mudflats and a perennial form is common in subtidal areas. Where lowtide water depth was greater than winter ice thickness (∼25 cm), ice movement removed much of the aboveground biomass from perennial ramets, but did not influence the density of ramets. Measurements of primary production showed that perennial plants allocated a greater proportion of their total production to below-ground structures than measured in all previous studies on eelgrass. Thus perennials are well anchored in the sediment, are more able to withstand removal by ice, and have reserves available for production of new leaves when ice melts. In the spring, seed germination was greatest in areas where ice had removed whole plants (or their aboveground parts) than among mature ramets which had survived winter intact. Survival of seedlings (new genets) was not affected by shading from the adult canopy, but a shading experiment showed that competition for light with mature ramets had a significant negative effect on morphology, growth and the allocation of seedling biomass to below-ground parts, thus reducing the ability of new genets to survive ice disturbance in the next winter. The annual form ofZ. marina was restricted to areas where low tide water depth was much less than winter ice thickness. Annual plants did not survive winter, had small investment in below-ground parts and high reproductive effort, and overwintered as seeds. The genetic status of the two forms and the restriction of the annual to very shallow water are discussed in the light of previous work on eelgrass

Journal ArticleDOI
01 Dec 1984
TL;DR: Reduced 14CO2 production in exercise after other substrates is consistent with this, suggesting muscle carbohydrate reserves may be exclusively for locomotion, and a 5‐fold increase during forced exercise after fasting by octopuses given glucose may indicate increased carbohydrate catabolism.
Abstract: Average absorption and conversion to 14CO2for free leucine included in a meal were 96% and 30% after 24 h. The values for glucose were 98% and 48% and for palmitate 46% and 12.5%. Muscle was the major repository of leucine (38% of the total ingested) and glucose (44%), but the digestive gland contained most of the palmitate (20%). During normal feeding 14CO2 production from octopuses given leucine dropped to low stable levels after only 2 days, those given glucose required 4 to 5, but palmitate apparently did not enter a stable reserve. Fasting increased the release of 14CO2 from octopuses given palmitate and leucine, but glucose animals showed little change. A 5‐fold increase in 14CO2 production during forced exercise after fasting by octopuses given glucose may indicate increased carbohydrate catabolism. Reduced 14CO2production in exercise after other substrates is consistent with this, suggesting muscle carbohydrate reserves may be exclusively for locomotion. A comparison of nutrient uptake, catabolism...

Journal ArticleDOI
TL;DR: This work compared the visual detection of such camouflaged objects with the detection of objects whose boundaries were defined by luminance contrast, finding that the effect of eccentricity on threshold is less for large objects than for small objects.
Abstract: Some naturally camouflaged objects are invisible unless they move; their boundaries are then defined by motion contrast between object and background. We compared the visual detection of such camouflaged objects with the detection of objects whose boundaries were defined by luminance contrast. The summation field area is 0.16 deg2 , and the summation time constant is 750 msec for parafoveally viewed objects whose boundaries are defined by motion contrast; these values are, respectively, about 5 and 12 times larger than the corresponding values for objects defined by luminance contrast. The log detection threshold is proportional to the eccentricity for a camouflaged object of constant area. The effect of eccentricity on threshold is less for large objects than for small objects. The log summation field diameter for detecting camouflaged objects is roughly proportional to the eccentricity, increasing to about 20 deg at 32-deg eccentricity. In contrast to the 100:1 increase of summation area for detecting camouflaged objects, the temporal summation time constant changes by only 40% between eccentricities of 0 and 16 deg.

Journal ArticleDOI
TL;DR: An alternative method of cervical fixation utilizing a stainless steel clamp is described, which has been most satisfactory in the long term results.
Abstract: An alternative method of cervical fixation utilizing a stainless steel clamp is described. The clamp is applied to the adjoining laminae of involved vertebrae in those cervical dislocations and subluxations with posterior instability. The long term results of this method have been most satisfactory,

Journal ArticleDOI
TL;DR: Atavism can be produced by experimental manipulation within developing systems ‐increased growth of the chick fibula, enamel production from avian ectoderm, and balancer formation in amphibians.
Abstract: Summary 1. Atavisms emerge as evidence of localized modifications in development of an organ or of one of its parts. Different developmental processes can be triggered within the same organ rudiment, presumably in response to the same stimulus. We saw that that stimulus can have a genetic basis in a mutational event, which can be selected for. We also saw that atavism can be produced by experimental manipulation within developing systems -increased growth of the chick fibula, enamel production from avian ectoderm, and balancer formation in amphibians. Such atavisms are not based on heritable genetic changes. They indicate the developmental plasticity that exists within embryos and the relative ease with which development can be switched from one programme to another. 2. Examination of mutants (wingless chicks), limbless vertebrates and experimental manipulation of embryos, shows that cell death, inductive tissue interactions and altered patterns of growth are developmental mechanisms used in the formation of atavisms. 3. Differential development mechanisms can be triggered within the same organ at the same time to produce atavisms. In the guinea pig, formation of atavistic digit V involves prolongation of growth of metatarsal V whereas formation of atavistic digit I involves development of a new metatarsal I. 4. Secondary functional modifications ensure that the atavism is integrated with the other components of the functional unit, as illustrated by extra digits in horses or guinea pigs and fibulae in birds. Atavistic 2nd and 4th digits in horses arise by continued growth of their primordia. A consequent reduction in the growth rate of digit 3, the normal single functional digit, enables all three digits to attain approximately equal lengths and so potentially to function. The altered functional load transmitted to the limbs results in secondary but correlated alterations in muscles and skeletal elements in other portions of the limbs. The fact that embryonic digit 2 normally develops to a more advanced state than digit 4 explains why digit 2 more often develops atavistically, for if variation in growth rate is the basis for the atavistic digit, digit 2 has an advantage over digit 4. 5. Atavisms should not be an embarrassment to the evolutionary biologist. They are the outward and visible sign of a hidden potential for morphology change possessed by all organisms. Neither basic capacity to form the organ nor patterning information is lost. Modification of components of inductive tissue interactions helps to explain how organs are lost during evolution (also see Regal, 1977); retention of the basic mechanism explains how structures can be revived as atavisms (also see Rachootin & Thomson, 1981). Frequency of atavisms thus provides an indication of the degree of modification or loss of the underlying developmental programme.

Journal ArticleDOI
TL;DR: The value of the stable carbon isotope ratio as a tracer in food webs involving macroalgae is questioned, but for Z. marina, in which the values are seasonally predictable, the technique may be useful if interpreted with care.
Abstract: Stable carbon isotope ratios (δ13C) of eelgrass Zostera marina and of kelp Laminaria longicruris showed considerable variation in time and space. The isotopic composition of Z. marina varied seasonally from a mean of-6‰ for leaves formed in June to a mean of-10‰ for leaves formed in February. The maximum range for individual leaves was from-5 to-11.4‰. Once a leaf was fully formed, its isotopic composition appeared not to change. In L. longicruris there was no clear seasonal pattern of variation, but in any given blade there was a spatial pattern of variation, with the thickened central band tending to be least negative and the margins most negative. In one blade the range was from-12 to-20‰. Since this range overlaps values that are found in various other macrophytes and in seston, the value of the stable carbon isotope ratio as a tracer in food webs involving macroalgae is questioned. For Z. marina, in which the values are seasonally predictable, the technique may be useful if interpreted with care. The most probable explanation of variation in the ratios is differential storage of biochemical components of different isotopic compostion.

Journal ArticleDOI
TL;DR: Measurements of rates of feeding indicate that Euphausia superba can feed on particles ranging from nanophytoplankton to macrozooplankton; a typical animal of 120 mg dry weight processes about 450 ml water per h and eats at a maximum about 10% of its body carbon per day.
Abstract: Measurements of rates of feeding indicate that Euphausia superba can feed on particles ranging from nanophytoplankton to macrozooplankton; a typical animal of 120 mg dry weight processes about 450 ml water per h and ingests at a maximum about 10% of its body carbon per day A food concentration of about 100 µg carbon 1–1 allows the animal to ingest its minimum food requirement of 23% body carbon per day Measurements of 210Po and 210Pb indicate krill from Bransfield Strait in February 1982 were feeding herbivorously Photographic analysis of the thoracic legs employed by E superba for feeding indicates that the mechanical power required to extract phytoplankton from the water ranges up to about 30% of its total respiratory energy

Journal ArticleDOI
TL;DR: The perspective offered here is that to understand the development of coordinated action it is valuable to seek relative degrees of continuity-discontinuity and change-stability from several complementary perspectives, which provides the flexibility necessary to clarify underlying developmental pathways.
Abstract: My concern in this paper is to provide a framework for analyzing the development of coordinated action systems. By emphasizing the general theme of pattern formation in coordinated action, attention is drawn to dual problems of establishing separable dimensions of action that are in turn combined into higher-order configurations. During development processes of differentiation and integration are combined to make coordinated action possible. The rules by which this is accomplished, however, are still poorly understood. The perspective offered here is that to understand the development of coordinated action it is valuable to seek relative degrees of continuity-discontinuity and change-stability from several complementary perspectives. This avoids unnecessarily simple "unit" concepts of coordinated action, and thereby provides the flexibility necessary to clarify underlying developmental pathways.

Journal ArticleDOI
01 Jan 1984
TL;DR: The concept of local development is defined as a particular form of regional development, one in which endogenous factors occupy a central position as mentioned in this paper, where the roles of the entrepreneur and of human capital in the process of economic growth are examined.
Abstract: The concept of local development is defined as a particular form of regional development, one in which endogenous factors occupy a central position A stages model of local development is proposed: 1) the emergence of local entrepreneurship; 2) the “take off” of local enterprises; 3) the expansion of these enterprises beyond the local region; and 4) the achievement of a regional economic structure that is based upon local initiatives and locally created comparative advantages The theoretical and empirical foundations of this model are examined, with particular emphasis upon the roles of the entrepreneur and of human capital in the process of economic growth, and upon the spatial effects of the expansion of the firm

OtherDOI
TL;DR: The sections in this article are: Development of Visual Perception, Functional Role of Visual Experience, Genetic and Experiential Factors in Visual Development, and Effects of Unusual Visual Input on Cortical Development.
Abstract: The sections in this article are: 1 Development of Visual Perception 1.1 Methods of Study 1.2 Development of Spatial Resolution 1.3 Development of Depth Perception and Stereopsis 1.4 Overview 2 Development of Visual Neural Processes 2.1 Retina 2.2 Lateral Geniculate Nucleus 2.3 Visual Cortex 3 Consequences of Binocular Visual Deprivation 3.1 Forms of Binocular Deprivation 3.2 Effects on Perception 4 Effects of Selected Visual Experience on Neural Processes and Perception 5 Conditions that Influence Ocular Dominance 5.1 Monocular Deprivation 5.2 Artificial Strabismus 5.3 Alternating Monocular Deprivation 6 Conditions that Influence Other Receptive-Field Properties 6.1 Orientation Selectivity 6.2 Movement and Direction Selectivity 6.3 Effects of Unusual Visual Input on Cortical Development 7 Genetic and Experiential Factors in Visual Development 7.1 Functional Role of Visual Experience

Journal ArticleDOI
TL;DR: Most of the children with unilateral temporal lobe epilepsy had no measurable cognitive or emotional difficulties and were not identified by the PIC as maladjusted, but as a group showed significantly lower neuropsychological test functioning than did the normally adjusted children.
Abstract: By reviewing electroencephalographic reports compiled over five years and checking clinical details, we identified and studied 27 children with apparently pure left or pure right temporal lobe epilepsy. The children underwent neurological examination and neuropsychological testing (Halstead-Reitan Battery, Wechsler Intelligence Scale for Children [WISC] and Wide Range Achievement Test), and parents completed the Personality Inventory for Children (PIC). Of 15 boys and 12 girls with a mean age of 12.7 years, 14 had right and 13 left temporal lobe epilepsy. Seizure control was excellent in 17. Five (2 with left, 3 with right temporal lobe epilepsy) had received professional emotional help, 6 (3 with left, 3 with right focus) received special help at school, and 5 (3 with left, 2 with right focus) had failed a grade in school. No significant left-right differences were seen in WISC full scale, verbal, or performance IQ scores, neuropsychological test battery findings, or clinical scale scores on the PIC. Most of the children with unilateral temporal lobe epilepsy had no measurable cognitive or emotional difficulties. Cognitive, personality, and school problems were equally distributed between left and right temporal lobe epilepsy groups. When the two groups were combined, however, 10 patients (5 with left, 5 with right focus) were identified by the PIC as maladjusted, and as a group showed significantly lower neuropsychological test functioning than did the normally adjusted children.

Journal ArticleDOI
TL;DR: In this article, the results indicate significant paleoceanographic shifts along a north-south gradient both prior to and during the Holocene in the Emerald, Canso and Notre Dame basins using 14C dates and pollen stratigraphies.

Journal ArticleDOI
TL;DR: It is concluded that 18S + 5S rRNA genes are located at several distinct sites in the wheat mitochondrial genome, and it is suggested that reciprocal intra‐ and/or intermolecular recombination between such repeated sequences could promote extensive genomic rearrangement and thus contribute to the physical heterogeneity that is a hallmark of most plant mitochondrial DNAs.
Abstract: Closely linked genes for 18S and 5S rRNAs have been located on four different cloned SalI restriction fragments of wheat (Triticum aestivum L.) mitochondrial DNA. Restriction analysis has revealed that in each of the cloned fragments, the 18S and 5S rRNA genes are contained within the same basic structural unit, R, which is at least 4 kbp long. This unit is flanked by sequences designated u (0.8 kbp), v (13.7 kbp), w (0.7 kbp), and y (1.4 kbp), in the orientations v-R-w, v-R-y, u-R-w, and u-R-y in the four different SalI fragments. We conclude that 18S + 5S rRNA genes are located at several distinct sites in the wheat mitochondrial genome, and suggest that reciprocal intra- and/or intermolecular recombination between such repeated sequences could promote extensive genomic rearrangement and thus contribute to the physical heterogeneity that is a hallmark of most plant mitochondrial DNAs.

Journal ArticleDOI
TL;DR: The relationship between neurological urinary symptoms and urodynamic findings in patients with multiple sclerosis was examined and positive correlation was found between urge incontinence anddetrusor hyperreflexia, and between hesitancy and detrusor areflexia but no relationship was foundBetween urological symptoms and sphincter function.

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TL;DR: Seven Azospirillum strains induced more deformation of root hairs of wheat than did strains of Rhizobium leguminosarum, Azotobacter chroococcum, or Escherichia coli.
Abstract: Seven Azospirillum strains induced more deformation of root hairs of wheat than did strains of Rhizobium leguminosarum, Azotobacter chroococcum, or Escherichia coli. Azospirillum sp. strain Sp245 caused the most deformation. Strain Sp245 (isolated from surface sterile roots of wheat) and strain Sp7 (isolated from the rhizosphere of a forage grass) were compared with regard to their effects on root hair deformation, their attachment to roots, and their effects on the growth of four wheat cultivars. The amount of deformation caused by the two strains in the four cultivars increased in the following order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Strain Sp245 attached to the roots of all cultivars in low numbers, and attachment did not increase with time (up to 48 h). Strain Sp7 attached in higher numbers, and attachment increased with time. Inoculation of the four cultivars of wheat had pronounced effects on root mass measured at maturity. The magnitude of the effects in the four cultivars increased in the following order: Tobari, Tonari, BH1146, Lagoa; these effects were progressively more positive for strain Sp245 and progressively more negative for strain Sp7. Concentrations of N in wheat did not vary substantially between cultivars or strains. Concentrations of K and P did not vary substantially between cultivars but did vary between strains, Sp245 effecting increases and Sp7 effecting decreases.