Showing papers by "University of North Carolina at Chapel Hill published in 1987"
01 Sep 1987-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: It is concluded that clipped ahe should become a method of choice in medical imaging and probably also in other areas of digital imaging, and that clip ahe can be made adequately fast to be routinely applied in the normal display sequence.
Abstract: Adaptive histogram equalization (ahe) is a contrast enhancement method designed to be broadly applicable and having demonstrated effectiveness. However, slow speed and the overenhancement of noise it produces in relatively homogeneous regions are two problems. We report algorithms designed to overcome these and other concerns. These algorithms include interpolated ahe, to speed up the method on general purpose computers; a version of interpolated ahe designed to run in a few seconds on feedback processors; a version of full ahe designed to run in under one second on custom VLSI hardware; weighted ahe, designed to improve the quality of the result by emphasizing pixels' contribution to the histogram in relation to their nearness to the result pixel; and clipped ahe, designed to overcome the problem of overenhancement of noise contrast. We conclude that clipped ahe should become a method of choice in medical imaging and probably also in other areas of digital imaging, and that clipped ahe can be made adequately fast to be routinely applied in the normal display sequence.
3,041 citations
TL;DR: In this article, the authors examine both the nature of the software problem and the properties of the bullets proposed, and show that there is no single development, in either technology or in management technique, that by itself promises even one order-of-magnitude improvement in productivity, in reliability, in simplicity.
Abstract: But, as we look to the horizon of a decade hence, we see no silver bullet. There is no single development, in either technology or in management technique, that by itself promises even one order-of-magnitude improvement in productivity, in reliability, in simplicity. In this article, I shall try to show why, by examining both the nature of the software problem and the properties of the bullets proposed.
2,794 citations
01 Jan 1987
TL;DR: In this article, a 6-dimensional hyperbolic Riemannian manifold is introduced, which takes for its metric the coefficient of the momenta in the Hamiltonian constraint and the geodesic incompletability of this manifold, owing to the existence of a frontier of infinite curvature, is demonstrated.
Abstract: Following an historical introduction, the conventional canonical formulation of general relativity theory is presented. The canonical Lagrangian is expressed in terms of the extrinsic and intrinsic curvatures of the hypersurface ${x}^{0}=\mathrm{constant}$, and its relation to the asymptotic field energy in an infinite world is noted. The distinction between finite and infinite worlds is emphasized. In the quantum theory the primary and secondary constraints become conditions on the state vector, and in the case of finite worlds these conditions alone govern the dynamics. A resolution of the factor-ordering problem is proposed, and the consistency of the constraints is demonstrated. A 6-dimensional hyperbolic Riemannian manifold is introduced which takes for its metric the coefficient of the momenta in the Hamiltonian constraint. The geodesic incompletability of this manifold, owing to the existence of a frontier of infinite curvature, is demonstrated. The possibility is explored of relating this manifold to an infinite-dimensional manifold of 3-geometries, and of relating the structure of the latter manifold in turn to the dynamical behavior of space-time. The problem is approached through the WKB approximation and Hamilton-Jacobi theory. Einstein's equations are revealed as geodesic equations in the manifold of 3-geometries, modified by the presence of a "force term." The classical phenomenon of gravitational collapse shows that the force term is not powerful enough to prevent the trajectory of space-time from running into the frontier. The as-yet unresolved problem of determining when the collapse phenomenon represents a real barrier to the quantum-state functional is briefly discussed, and a boundary condition at the barrier is proposed. The state functional of a finite world can depend only on the 3-geometry of the hypersurface ${x}^{0}=\mathrm{constant}$. The label ${x}^{0}$ itself is irrelevant, and "time" must be determined intrinsically. A natural definition for the inner product of two such state functionals is introduced which, however, encounters difficulties with negative probabilities owing to the barrier boundary condition. In order to resolve these difficulties, a simplified model, the quantized Friedmann universe, is studied in detail. In order to obtain nonstatic wave functions which resemble a universe evolving, it is necessary to introduce a clock. In order that the combined wave functions of universe-cum-clock be normalizable, it turns out that the periods of universe and clock must be commensurable. Wave packets exhibiting quasiclassical behavior are constructed, and attention is called to the phenomenological character of "time." The innerproduct definition is rescued from its negative-probability difficulties by making use of the fact that probability flows in a closed finite circuit in configuration space. The article ends with some speculations on the uniqueness of the state functional of the actual universe. It is suggested that a viewpoint due to Everett should be adopted in its interpretation.
1,846 citations
Book•
01 Jan 1987TL;DR: In this paper, the authors introduce the leading marketing thinking on how customer value is the driving force behind every marketing strategy, focusing on customer relationships, the creation of value and brand equity.
Abstract: Introduces the leading marketing thinking on how customer value is the driving force behind every marketing strategy. The book's strength lies in the many international practical examples and real-world cases. Special attention to customer relationships, the creation of value and brand equity reflects well today's marketing requirements. A focus on the ever-increasing importance of new technologies makes this book invaluable for business schools – in the UK and abroad.
1,288 citations
TL;DR: A crucial question is whether Zipf's law of word occurrence should be considered a part of this particular sub-discipline of ‘bibliometrics’.
Abstract: The definitions of the term ‘bibliometrics’ as used in the literature are examined and evaluated. Most such definitions are held to be too broad. A new definition is proposed; then its advantages and possible defects pointed out. A crucial question is whether Zipf's law of word occurrence should be considered a part of this particular sub-discipline.
776 citations
TL;DR: In this paper, the effects of giving acausal account, or a justification versus not providing a justification, on judgments of interactional fairness and endorsement of a decision maker's actions were examined.
Abstract: There has been an increasing amount of research conducted on issues of procedural justice. Although this research has demonstrated that the type of procedure used to allocate outcomes has an independent influence on people's judgments of the fairness of a decision, there is growing empirical evidence that such judgments are influenced by the enactment of the procedure as well. Fairness concerns raised about the propriety of a decision maker's behavior during the enactment of procedures are representative of a desire forinteractional justice. In this paper, we present three studies that examine the effects of giving acausal account, or a justification, versus not providing a justification, on judgments of interactional fairness and endorsement of a decision maker's actions. In Study I, a laboratory study, ratings of interactional fairness and support for a manager were higher when subjects received a causal account that claimed mitigating circumstances for a manager's improper action than when they did not receive such a causal account. A second laboratory study replicated the same pattern of findings in two different organizational contexts. In addition, it was found that the perceived adequacy of the causal account was a critical factor explaining its effect. In Study 3, a field setting, ratings of both interactional fairness and procedural fairness were higher when a manager provided anadequate causal account to justify the allocation of an unfavorable outcome. The discussion focuses on the implications of these findings for research on interactional and procedural justice.
735 citations
TL;DR: It is concluded that a form of IGF binding protein that is present in extracellular fluids and is secreted by many types of cells can markedly potentiate the cellular response to IGF-I.
Abstract: The insulin-like growth factors IGF-I and IGF-II circulate in blood bound to carrier proteins. The higher molecular mass IGF-binding protein complex (150 kDa) is composed of subunits, and one subunit that forms this complex is growth hormone dependent. In addition, many cell types and tissues secrete another form of IGF binding protein that is not growth hormone dependent. Both forms of the IGF binding protein are believed to inactivate the IGFs and to function as delivery systems to tissues. This conclusion was based on studies that determined the effects of impure preparations of these binding proteins or that examined the effect of these proteins only on the insulin-like actions of the IGFs. We report here that a pure preparation of the extracellular form of the IGF binding protein (purified from human amniotic fluid) markedly potentiated replication of several cell types in response to human IGF-I. Secondary cultures of human, mouse, and chicken embryo fibroblasts as well as porcine aortic smooth muscle cells showed marked enhancement of their DNA synthesis response (2.8- to 4.4-fold increases) to IGF-I in the presence of this protein. These responses were synergistic since the sum of the responses to either IGF-I or to the binding protein alone was between 8 and 17% of the increase obtained in cultures exposed to both peptides. The binding protein not only potentiated the DNA synthesis response but also enhanced the increase in cell number in response to IGF-I. This stimulation is specific for growth factors that bind to the binding protein since incubation with insulin, which binds to the type I IGF receptor but not to the binding protein, did not result in potentiation of this response. We conclude that a form of IGF binding protein that is present in extracellular fluids and is secreted by many types of cells can markedly potentiate the cellular response to IGF-I.
707 citations
TL;DR: It is concluded that heterozygous carriers of the gene for ataxia-telangiectasia have an excess risk of cancer, particularly breast cancer in women.
Abstract: Patients who are homozygous for ataxia-telangiectasia have an exceptionally high incidence of cancer. In a group of families expected to have a high proportion of heterozygotes for ataxia-telangiectasia, we tested the hypothesis that such heterozygotes, estimated to make up 0.68 to 7.7 percent of the U.S. white population, also have an excess cancer risk. Retrospective cancer incidence rates in adult blood relatives of patients with ataxia-telangiectasia in 110 white non-Amish families were significantly elevated over the incidence rates in spouse controls (rate ratios, 1.6 for men [P = 0.032]; 2.0 for women [P = 0.013]). For persons who are heterozygous for ataxia-telangiectasia, the relative risk of cancer was estimated to be 2.3 for men (P = 0.014) and 3.1 for women (P = 0.004). Breast cancer in women was the cancer most clearly associated with heterozygosity for ataxia-telangiectasia (rate ratio, 3.0 [P = 0.028]; heterozygote relative risk, 6.8 [P = 0.006]). On the basis of this estimated relative risk of 6.8 and an estimated heterozygote frequency in the general population of 1.4 percent, 8.8 percent of patients with breast cancer in the U.S. white population would be heterozygous for ataxia-telangiectasia. We conclude that heterozygous carriers of the gene for ataxia-telangiectasia have an excess risk of cancer, particularly breast cancer in women.
701 citations
TL;DR: In this article, the variance function estimation in heteroscedastic regression models is studied in a unified way, focusing on common methods proposed in the statistical and other literature, to make both general observations and compare different estimation schemes.
Abstract: Heteroscedastic regression models are used in fields including economics, engineering, and the biological and physical sciences. Often, the heteroscedasticity is modeled as a function of the covariates or the regression and other structural parameters. Standard asymptotic theory implies that how one estimates the variance function, in particular the structural parameters, has no effect on the first-order properties of the regression parameter estimates; there is evidence, however, both in practice and higher-order theory to suggest that how one estimates the variance function does matter. Further, in some settings, estimation of the variance function is of independent interest or plays an important role in estimation of other quantities. In this article, we study variance function estimation in a unified way, focusing on common methods proposed in the statistical and other literature, to make both general observations and compare different estimation schemes. We show that there are significant di...
697 citations
TL;DR: By in situ hybridization histochemistry, IGF I (somatomedin C) and IGF II messenger RNAs were localized to connective tissues or cells of mesenchymal origin in 14 organs and tissues from human fetuses.
Abstract: The somatomedins or insulin-like growth factors (IGFs) are synthesized in many organs and tissues, but the specific cells that synthesize them in vivo have not been defined. By in situ hybridization histochemistry, IGF I (somatomedin C) and IGF II messenger RNAs were localized to connective tissues or cells of mesenchymal origin in 14 organs and tissues from human fetuses. IGF messenger RNAs were localized to perisinusoidal cells of liver, to perichondrium of cartilage, to sclera of eye, and to connective tissue layers, sheaths, septa, and capsules of each organ and tissue. All of the hybridizing regions are comprised predominantly of fibroblasts or other cells of mesenchymal origin. Because these cells are widely distributed and anatomically integrated into tissues and organs, they are ideally located for production of IGFs, which may exert paracrine effects on nearby target cells.
671 citations
TL;DR: It is shown that coagulase-negative staphylococci are the most common agents responsible for peritonitis in patients undergoing continuous ambulatory peritoneal dialysi and that vancomycin has beco e the resistance of methicilli.
Abstract: COAGULASE-negative staphylococci have been11 increasilgly recognized as causative agents in sevel l types of infection, including nosocomial bacteremia and infection of indwelling devices, such as prosthetic hea t valv1 , 2 2 a d neurosurgical and arteriovenous shunt3 , 4 4 Coagulase-negative staphylococci are also the most common agents responsible for peritonitis in patients undergoing continuous ambulatory peritoneal dialysi5 6 7 8 9 10 Until recentl, beta-lactamase-stable penicillins we e regarded as t e treatmen s f choi e f r staphylococcal infections. Unfortunately, 35 t66 6 percent of clinically important coagulase-negative staphylococcal isolates are currently resista t o methicilli11 12 13 14 15c As a result, vancomycin has beco e the . . .
TL;DR: This paper provides a tuple relational calculus semantics for the TQuel statements that differ from their Quel counterparts, including the modification statements, and discusses reducibility of the semantics to Quel's semantics when applied to a static database.
Abstract: Recently, attention has been focused on temporal databases, representing an enterprise over time. We have developed a new language, Tquel, to query a temporal database. TQuel was designed to be a minimal extension, both syntactically and semantically, of Quel, the query language in the Ingres relational database management system. This paper discusses the language informally, then provides a tuple relational calculus semantics for the TQuel statements that differ from their Quel counterparts, including the modification statements. The three additional temporal constructs defined in Tquel are shown to be direct semantic analogues of Quel's where clause and target list. We also discuss reducibility of the semantics to Quel's semantics when applied to a static database. TQuel is compared with ten other query languages supporting time.
TL;DR: Ryanodine affects excitation-contraction coupling in skeletal and cardiac muscle by specifically interacting with the sarcoplasmic reticulum Ca2+ release channel by increasing the open probability of the channels in such a way that Po was close to unity under a variety of activating and inactivating conditions.
Abstract: Ryanodine affects excitation-contraction coupling in skeletal and cardiac muscle by specifically interacting with the sarcoplasmic reticulum (SR) Ca2+ release channel. The effect of the drug at the single channel level was studied by incorporating skeletal and cardiac SR vesicles into planar lipid bilayers. The two channels were activated by micromolar free Ca2+ and millimolar ATP and inhibited by Mg2+ and ruthenium red. Addition of micromolar concentrations of ryanodine decreased about twofold the unit conductance of the Ca2+- and ATP-activated skeletal and cardiac channels. A second effect of ryanodine was to increase the open probability (Po) of the channels in such a way that Po was close to unity under a variety of activating and inactivating conditions. The effects of ryanodine were long lasting in that removal of ryanodine by perfusion did not return the channels into their fully conducting state.
TL;DR: Overall, the findings revealed significant, durable effects of treatment that differed somewhat with client age and treatment method but were reliably greater than zero for most groups, most problems, and most methods.
Abstract: How effective is psychotherapy with children and adolescents? The question was addressed by metaanalysis of 108 well-designed outcome studies with 4-18-year-old participants. Across various outcome measures, the average treated youngster was better adjusted after treatment than 79% of those not treated. Therapy proved rnore effective for children than for adolescents, particularly when the therapists were paraprofessionals (e.g., parents, teachers) or graduate students. Professionals (with doctor's or master's degrees) were especially effective in treating overcontrolled problems (e.g., phobias, shyness) but were not more effective than other therapists in treating undercontrolled problems (e.g., aggression, impulsivity). Behavioral treatments proved more effective than nonbehavioral treatments regardless of client age, therapist experience, or treated problem. Overall, the findings revealed significant, durable effects of treatment that differed somewhat with client age and treatment method but were reliably greater than zero for most groups, most problems, and most methods.
TL;DR: It is found that after 'chemical hypoxia' with cyanide and iodoacetate, cytosolic free Ca2+ does not change during bleb formation or before loss of cellular viability.
Abstract: Cell surface 'blebbing' is an early consequence of hypoxic and toxic injury to cells. A rise in cytosolic free Ca2+ has been suggested as the stimulus for bleb formation and the final common pathway to irreversible cell injury. Here, using digitized low-light video microscopy, we examine blebbing, cytosolic free Ca2+, mitochondrial membrane potential and loss of cell viability in individual cultured hepatocytes. Unexpectedly, we found that after 'chemical hypoxia' with cyanide and iodoacetate, cytosolic free Ca2+ does not change during bleb formation or before loss of cellular viability. Cell death was precipitated by a sudden breakdown of the plasma membrane permeability barrier, possibly caused by rupture of a cell surface bleb.
TL;DR: It is found that measures that account for ordering on the base variable proved to be more highly correlated with subjects' actual similarity judgments, and, surprisingly, the best measures were ones that focus on only one “slice” of the membership function.
TL;DR: The surgical approach to bleeding visceral artery aneurysms has a mortality rate of 16-50% that is dependent primarily on anatomic location and underlying cause, and there was a 79% success rate and no mortality in patients studied.
Abstract: The surgical approach to bleeding visceral artery aneurysms has a mortality rate of 16-50% that is dependent primarily on anatomic location and underlying cause. Nineteen patients were studied over a 10-year period who were definitively treated by embolization. There was a 79% success rate and no mortality. The cause of the aneurysms was pancreatitis in 13 patients, trauma in four patients, subacute bacterial endocarditis in one patient, and secondary to biliary tract surgery in one patient.
TL;DR: In this paper, the properties of cobalt tetrakis(o-aminopheny1) porphyrin polymers are described and compared to those of polypyrin solutions in acetonitrile or methylene chloride.
Abstract: are described. Oxidations of these monomers lead to thin polymeric coatings on electrodes by coupling reactions analogous to those operative in polyaniline, polypyrrole, and polyphenol electropolymerization. The films contain from two to several hundred layers of porphyrin sites and display reductive electrochemical and electronic spectroscopic properties similar to those of monomer solutions in acetonitrile or methylene chloride. The pyrtolyl- and amino-based polymers are polycationic and thus anion exchangers, whereas the hydroxy-based polymers (at pH >8) are polyanionic. Films prepared from electropolymerization of cobalt tetrakis(o-aminopheny1)porphyrin display a split Co(III/II) wave in aqueous acid and base and are good oxygen reduction catalysts, whereas films prepared from all other cobalt porphyrin monomers display only one Co(III/II) wave and are poor catalysts.
TL;DR: A vew of planning appropriate for the 1990's is described and contributions form the information technology (IT) planning literature likely to facilitate IT planning efforts are identified.
Abstract: Although planning is a crucial information management issue, it must be seen as only one facet of an organization's complete program for information technology management. Attention in this article is first directed toward understanding the larger management context within which planning activities are likely to transpire. The paper then describes a vew of planning appropriate for the 1990's and identifies contributions form the information technology (IT) planning literature likely to facilitate IT planning efforts.
TL;DR: The validity of the syndrome is reviewed based on the last review (Rutter, 1978; Schopler, 1978), and controversies over both the boundaries and the heterogeneity within the autism syndrome are evaluated.
Abstract: The purpose of this report is to bring up to date available information on the defining features and diagnostic issues relating to autism and related disorders We review the validity of the syndrome based on our last review (Rutter, 1978; Schopler, 1978) Subsequent data have produced refinement in our understanding of both diagnostic criteria and the nature of the basic deficit Controversies over both the boundaries and the heterogeneity within the autism syndrome are evaluated according to available evidence Diagnostic rating instruments for expediting systematic sample selection are critiqued, and leads for new research directions are suggested
TL;DR: The spatial learning abilities of young, middle-age, and senescent rats were investigated in two experiments using several versions of the Morris water maze task and revealed that following cue training, young subjects exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training, while aged rats showed no spatial bias.
Abstract: The spatial learning abilities of young, middle-age, and senescent rats were investigated in two experiments using several versions of the Morns water maze task In Experiment 1, Long-Evans hooded rats were trained to find a submerged escape platform hidden within the water maze During this phase of testing, aged rats exhibited acquisition deficits compared with either young or middle-age subjects With continued training, however, all age groups eventually achieved comparable asymptotic levels of performance Subsequent testing in Experiment 1 revealed that following original training, aged rats were not impaired in learning a novel escape location or in their ability to locate a visible, cued escape platform In an attempt to identify the basis of the age-related impairments observed in Expenment I, naive young and aged rats in Experiment 2 were initially tested for their ability to locate a cued escape platform in the water maze During this phase of testing, the escape latencies of both young and aged rats rapidly decreased to equivalent asymptotic levels Subsequent analyses revealed that following cue training, young subjects exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training In contrast, aged rats showed no spatial bias Training was continued in Expenment 2 using a novel submerged platform location for each subject During these place training trials, the escape latencies of senescent rats were longer than those of young subjects These impairments were also accompanied by a lack of spatial bias among aged rats relative to young control subjects In combination, the results of these investigations indicate that age-related impairments in water maze performance reflect a specific deficit in the ability of aged rats to utilize spatial information In recent years the number of investigation s focusing on the identification of age-related changes in learning and memory has risen dramatically. Related to this intensified research effort is an increasing growth in the proportion of aged individuals in the population Because the incidence of various forms of cognitive deterioration is well documented to increase with increasing age (Botwimck, 1978), an important focus of current research is to delineate age-related changes in learning and memory in laboratory animals Such investigations may, therefore, highlight specific cognitive processes that are compromised in senescence, as well as provide insight into possible neural sites and mechanisms of senescent memory decline. In this context, a number of investigations utilizing a wide range of behavioral testing procedures have demonstrated that the performance of aged animals is impaired relative to young subjects (see Kubams & Zometzer, 1981, for a recent review) Perhaps the most consistent finding across investigations using rodents is that aged rats are impaired in tasks that young animals solve using spatial information Specifically, spatial information processing in aged rats has been studied using a number of testing procedures including the Barnes hole-board task (Barnes, 1979, Barnes, Nadel, & Homg, 1980), the 8-arm
TL;DR: The VRNF gene is genetically linked to the locus encoding nerve growth factor receptor, located on the long arm of chromosome 17 in the region 17q12----17q22, and crossovers with the VRNF locus suggest that a mutation in the nerve growthFactor receptor gene itself is unlikely to be the fundamental defect responsible for the VR NF phenotype.
TL;DR: It appears that age-related changes are not consistently found on measures such as the activity of ChAT or the content of ACh in these regions, basal levels of A Ch release in cortex, and the number of cholinergic neurons in the basal forebrain.
TL;DR: In patients who had persistent pain and stiffness of the acromioclavicular joint, or in whom symptomatic post-traumatic arthritis developed, resection of the distal part of the clavicle reliably produced significant improvement.
Abstract: The cases of 127 patients who had an acute dislocation of the acromioclavicular joint were studied. Fifty-two patients, with an average follow-up of 10.8 years, were managed operatively, and seventy-five patients, with an average follow-up of 9.5 years, were managed non-operatively. Using a rating system that included subjective, objective, and roentgenographic criteria, it did not appear that reduction of the acromioclavicular joint was necessary to obtain consistently good results. Operative management, using either coracoclavicular or acromioclavicular fixation, was associated with a higher rate of complications than non-operative treatment. The use of a sling for four weeks without reduction of the joint, followed by a graduated exercise program, led to acceptable clinical results. In patients who had persistent pain and stiffness of the acromioclavicular joint, or in whom symptomatic post-traumatic arthritis developed, resection of the distal part of the clavicle reliably produced significant improvement.
TL;DR: Although bone marrow transplant recipients had an order-of-magnitude greater risk of nosocomial Aspergillus infection than other immunocompromised hosts, this risk could be eliminated by using HEPA filters with horizontal laminar airflow.
TL;DR: In this article, a complex least squares fitting of small-signal frequency response data at various immittance levels is presented, and a number of actual equivalent circuits used in the past for both liquid and solid electrolytes are presented and compared.
TL;DR: It is demonstrated that the immediately-early gene region of HCMV, in particular immediate-early region 2, trans-activates the expression of the bacterial gene chloramphenicol acetyltransferase that is fused to the HIV long terminal repeat and carried by plasmid pHIV-CAT.
Abstract: Almost all homosexual patients with acquired immunodeficiency syndrome are also actively infected with human cytomegalovirus (HCMV). We have hypothesized that an interaction between HCMV and human immunodeficiency virus (HIV), the agent that causes acquired immunodeficiency syndrome, may exist at a molecular level and contribute to the manifestations of HIV infection. In this report, we demonstrate that the immediate-early gene region of HCMV, in particular immediate-early region 2, trans-activates the expression of the bacterial gene chloramphenicol acetyltransferase that is fused to the HIV long terminal repeat and carried by plasmid pHIV-CAT. The HCMV immediate-early trans-activator increases the level of mRNA from the plasmid pHIV-CAT. The sequences of HIV that are responsive to trans-activation by the HCMV immediate-early region are distinct from HIV sequences that required for response to the HIV tat. The stimulation of HIV gene expression by HCMV gene functions could enhance the consequences of HIV infection in persons with previous or concurrent HCMV infection.
TL;DR: In this article, the authors present an overview of a project examining longitudinal trends as small streams gradually coalesce into large rivers, summarizing their results in a series of budgets and predictive equations describing changes in organic carbon dynamics and community structure.
Abstract: Ecosystem processes and community structure in running waters of the boreal forests of Quebec, Canada, are strongly influenced by climate and channel geomorphology. Here we present an overview of a project examining longitudinal trends as small streams gradually coalesce into large rivers, summarizing our results in a series of budgets and predictive equations describing changes in organic carbon dynamics and community structure. There were significant trends with stream order for 70% of the 73 components, processes, and ratios examined. Of 46 independent components examined, 63% showed a significant trend with stream order. As stream size increased from 1st to 9th order there was a decrease in total carbon inputs (i.e., precipitation, throughfall, primary production, and allochthonous materials) followed by a gradual increase due to greater primary production in streams >6th order. The standing stock of carbon decreased exponentially downstream, and total carbon outputs (i.e., respiration, leaching, methane evasion, and insect emergence) increased slightly downstream. Nevertheless, some ecosystem—level processes, as well as community structure, showed equivocal trends, which were apparently due to the hierarchical scale of examination and the relative degree of physicochemical vs. biological control, of the processes and communities. The data, when placed in a watershed perspective, showed that total carbon inputs were evenly distributed by stream order throughout the 19 871—km2 Moisie River drainage network. Most carbon was stored in the small 1st to 3rd order streams, whereas the majority of organic carbon was metabolized in the 7th to 9th order rivers. Fluvial transport of organic carbon to the Gulf of St. Lawrence was nearly three times that of the measured total annual input, suggesting that inputs of dissolved organic carbon in groundwater were more important than previously expected. Ecosystem—level measurements of carbon retention and utilization also showed significant trends with stream order. The spiraling length for carbon increased exponentially from 8—15 km in small streams to 426 km in the 9th order river. There was a concomitant decrease in reach retention with stream order, while the rate coefficient of respiration and rate of downstream movement increased with order. The stream metabolism index, a measure of ecosystem efficiency, increased from 1st to 7th order, thereafter decreasing as streams became larger. These trends with stream order were related to physical gradients in channel dimensions, hydrology, riparian influences, and sunlight. We conclude that these subarctic lotic ecosystems have numerous strong relationships with stream order and that the dynamics can be described by a relatively small set of predictive equations.