Showing papers by "Université de Montréal published in 1989"
TL;DR: In this article, the spatial heterogeneity of populations and communities plays a central role in many ecological theories, such as succession, adaptation, maintenance of species diversity, community stability, competition, predator-prey interactions, parasitism, epidemics and other natural catastrophes, ergoclines, and so on.
Abstract: The spatial heterogeneity of populations and communities plays a central role in many ecological theories, for instance the theories of succession, adaptation, maintenance of species diversity, community stability, competition, predator-prey interactions, parasitism, epidemics and other natural catastrophes, ergoclines, and so on. This paper will review how the spatial structure of biological populations and communities can be studied. We first demonstrate that many of the basic statistical methods used in ecological studies are impaired by autocorrelated data. Most if not all environmental data fall in this category. We will look briefly at ways of performing valid statistical tests in the presence of spatial autocorrelation. Methods now available for analysing the spatial structure of biological populations are described, and illustrated by vegetation data. These include various methods to test for the presence of spatial autocorrelation in the data: univariate methods (all-directional and two-dimensional spatial correlograms, and two-dimensional spectral analysis), and the multivariate Mantel test and Mantel correlogram; other descriptive methods of spatial structure: the univariate variogram, and the multivariate methods of clustering with spatial contiguity constraint; the partial Mantel test, presented here as a way of studying causal models that include space as an explanatory variable; and finally, various methods for mapping ecological variables and producing either univariate maps (interpolation, trend surface analysis, kriging) or maps of truly multivariate data (produced by constrained clustering). A table shows the methods classified in terms of the ecological questions they allow to resolve. Reference is made to available computer programs.
2,166 citations
TL;DR: A model for the transit assignment problem with a fixed set of transit lines is described, formulated as a linear programming problem of a size that increases linearly with the network size that solves the latter problem in polynomial time.
Abstract: We describe a model for the transit assignment problem with a fixed set of transit lines The traveler chooses the strategy that allows him or her to reach his or her destination at minimum expected cost First we consider the case in which no congestion effects occur For the special case in which the waiting time at a stop depends only on the combined frequency, the problem is formulated as a linear programming problem of a size that increases linearly with the network size A label-setting algorithm is developed that solves the latter problem in polynomial time Nonlinear cost extensions of the model are considered as well
753 citations
TL;DR: In this paper, a symmetric iterative interpolation process is defined using a base b and an even number of knots, and the main properties of this process come from an associated function F. The basic functional equation for F is that F(t/b) = [
Abstract: Using a base b and an even number of knots, we define a symmetric iterative interpolation process. The main properties of this process come from an associated function F. The basic functional equation for F is that F(t/b) = \([\sum
olimits_n {F(n/b)F(t - n)} ]\). We prove that F is a continuous positive definite function. We find almost precisely in which Lipschitz classes derivatives of F belong. If a function y is defined only on integers, this process extends y continuously to the real axis as \([y(t) = \sum
olimits_n {y(n)F(t - n)} ]\). Error bounds for this iterative interpolation are given.
667 citations
TL;DR: It is claimed that the differences between short-range and long-range motion phenomena are a direct consequence of the stimuli used in the two paradigms and are not evidence for the existence of two qualitatively different motion processes.
Abstract: Several authors have proposed that motion is analyzed by two separate processes: short-range and long-range. We claim that the differences between short-range and long-range motion phenomena are a direct consequence of the stimuli used in the two paradigms and are not evidence for the existence of two qualitatively different motion processes. We propose that a single style of motion analysis, similar to the well known Reichardt and Marr-Ullman motion detectors, underlies all motion phenomena. Although there are different detectors of this type specialized for different visual attributes (namely first-order and second-order stimuli), they all share the same mode of operation. We review the studies of second-order motion stimuli to show that they share the basic phenomena observed for first-order stimuli. The similarity across stimulus types suggests, not parallel streams of motion extraction, one short-range and passive and the other long-range and intelligent, but a concatenation of a common mode of initial motion extraction followed by a general inference process.
619 citations
TL;DR: The greater the degree of cell discharge variation associated with different actively maintained limb postures, the greater the activity changes caused by loads, and preliminary evidence suggests that phasic and tonic cell groups may be spatially segregated in the motor cortex.
Abstract: Shoulder joint-related motor cortex cells show continuously graded changes in activity, centered on a preferred movement direction, during active arm movements in 8 directions away from a central starting position (Georgopoulos et al., 1982). We demonstrate here that many of these cells show similar large continuously graded changes in discharge when the monkey compensates for inertial loads which pull the arm in 8 different directions. These load-dependent discharge variations are typically unimodal, centered on one load direction called the cell's load axis, and are often sufficiently continuous, symmetric, and broad as to show a good fit to a sinusoidal curve. A vectorial representation of cell activity indicates that the pattern of load-dependent activity changes in the population forms a signal whose direction is appropriate to compensate for the loads. The responses of single cells to different combinations of movement and load direction are often complex. Nevertheless, the mean activity of the sample population under any condition of movement direction and load direction can be described reasonably well by a simple linear summation of the movement-related discharge without any loads, and the change in tonic activity of the population caused by the load, measured prior to movement. The strength of the load-dependent discharge variation differs among cells. Cells can be sorted into 2 phasic and 2 tonic groups that show differing degrees of sensitivity to loads. In particular, it was found that the greater the degree of cell discharge variation associated with different actively maintained limb postures, the greater the activity changes caused by loads. No similar correlation was found for the degree of discharge variation during movement. Preliminary evidence suggests that phasic and tonic cell groups may be spatially segregated in the motor cortex. These observations are consistent with the idea that there exists in the motor cortex activity encoding aspects of movement kinematics, as well as movement dynamics. These observations are in agreement with studies of more distal arm joints, showing that the activity of certain motor cortex cells varies with the patterns of muscle activity and output forces required to produce a movement. These experiments extend the description of the control of the direction of movement of a multiple degree-of-freedom joint into the spatial (direction) domain to a greater extent than previously achieved.
606 citations
TL;DR: The variation method for one-dimensional (1D) profiles is presented and it is shown that, in the limit, it is equivalent to the classical box-counting method and the result is an algorithm for reliably estimating the fractal dimension of 1D profiles.
Abstract: There are many definitions of the fractal dimension of an object, including box dimension, Bouligand-Minkowski dimension, and intersection dimension. Although they are all equivalent in the continuous domain, they differ substantially when discretized and applied to digitized data. We show that the standard implementations of these definitions on self-affine curves with known fractal dimension (Weierstrass-Mandelbrot, Kiesswetter, fractional Brownian motion) yield results with significant errors. An analysis of the source of these errors leads to a new algorithm in one dimension, called the variation method, which yields accurate results. The variation method uses the notion of \ensuremath{\epsilon} oscillation to measure the amplitude of the one-dimensional function in an \ensuremath{\epsilon} neighborhood. The order of growth of the integral of the \ensuremath{\epsilon} oscillation (called the \ensuremath{\epsilon} variation), as \ensuremath{\epsilon} tends toward zero, is directly related to the fractal dimension. In this paper, we present the variation method for one-dimensional (1D) profiles and show that, in the limit, it is equivalent to the classical box-counting method. The result is an algorithm for reliably estimating the fractal dimension of 1D profiles; i.e., graphs of functions of a single variable. The algorithm is tested on profiles with known fractal dimension.
416 citations
TL;DR: These tumors appear to be an adequate model for human breast cancers overexpressing c-neu, and the expression of the activated c-NEu oncogene was necessary but not sufficient to induce malignant transformation of the mammary epithelial cells.
404 citations
TL;DR: Data confirm that both the speed and accuracy of detecting changes in noxious heat stimuli are decreased when the subject attends to another stimulus modality and show that direction of attention affects the perceived intensity and unpleasantness of painful stimuli in a similar manner.
Abstract: Both experimental and clinical studies have shown that psychological manipulations, such as hypnosis, behavioral modification and cognitive-behavioral therapy, can reduce reports of pain. Although these are complex procedures, one important variable common to each is direction of attention. We have previously demonstrated in both humans and monkeys a method for monitoring and manipulating attention toward or away from a painful stimulus and have shown that changes in the direction of attention alter the ability to discriminate noxious heat stimuli. The present study assessed whether these changes in discrimination were accompanied by changes in the perception of pain intensity and/or unpleasantness. These data confirm that both the speed and accuracy of detecting changes in noxious heat stimuli are decreased when the subject attends to another stimulus modality. In addition, they show that direction of attention affects the perceived intensity and unpleasantness of painful stimuli in a similar manner. Our previous findings of attention-related modulation of nociceptive neuronal activity in the medullary dorsal horn suggest that these attention-dependent changes in sensory-discriminative and affective components of pain are mediated at early stages of sensory processing.
368 citations
TL;DR: It is demonstrated that the cerebellum generates a signal that varies with the direction of movement of the proximal arm during normal aimed reaching movements and is consistent with a role in the control of the activity of muscles or muscle groups generating these movements.
Abstract: 1. Three monkeys were trained to make whole-arm reaching movements from a common central starting position toward eight radially arranged targets disposed at 45 degrees intervals. A sample of 312 c...
347 citations
Book•
01 Jan 1989TL;DR: Le Blanc and Frechette as mentioned in this paper investigated the factors that sustain the development of offending and the mechanisms which accelerate, stabilize, and decelerate the commission of crimes in criminal activity.
Abstract: Male Criminal Activity From Childhood Through Youth reports the results of a large longitudinal study from 1972 to 1985 on a sample of delinquents and a comparison sample of the population in Montreal A clarification emerges from this extensive study: how to describe criminal activity in a comprehensive theory of crime which integrates the offense, offending, and patterns of offending Using a developmental approach, Drs Le Blanc and Frechette observed a gradation of crimes with subjects progressing through five distinct stages of offending In all, the research investigates the factors that sustain the development of offending and the mechanisms which accelerate, stabilize, and decelerate the commission of crimes This book represents a significant advance in the understanding of the development of criminal activity"
339 citations
TL;DR: In this paper, the capacity of different sampling designs and sample sizes to detect the spatial structure of a sugar-maple (Acer saccharum L.) tree density data set gathered from a secondary growth forest of southwestern Quebec was compared.
Abstract: Using spatial analysis methods such as spatial autocorrelation coefficients (Moran’s I and Geary’s c) and kriging, we compare the capacity of different sampling designs and sample sizes to detect the spatial structure of a sugar-maple (Acer saccharum L.) tree density data set gathered from a secondary growth forest of southwestern Quebec. Three different types of subsampling designs (random, systematic and systematic-cluster) with small sample sizes (50 and 64 points), obtained from this larger data set (200 points), are evaluated. The sensitivity of the spatial methods in the detection and the reconstruction of spatial patterns following the application of the various subsampling designs is discussed. We find that the type of sampling design plays an important role in the capacity of autocorrelation coefficients to detect significant spatial autocorrelation, and in the ability to accurately reconstruct spatial patterns by kriging. Sampling designs that contain varying sampling steps, like random and systematic-cluster designs, seem more capable of detecting spatial structures than a systematic design.
TL;DR: This paper considers the vehicle routing problem with stochastic demands, and a new solution framework for the problem using Markovian decision processes is presented.
Abstract: This paper considers the vehicle routing problem with stochastic demands. The objective is to provide an overview of this problem, and to examine a variety of solution methodologies. The concepts and the main issues are reviewed along with some properties of optimal solutions. The existing stochastic mathematical programming formulations are presented and compared and a new formulation is proposed. A new solution framework for the problem using Markovian decision processes is then presented.
TL;DR: There are at least two pathways by which cAMP may decrease the number of beta 2 ARs in cells: one involves phosphorylation of the receptor by the cAMP-dependent protein kinase and the other leads to a reduction in steady state beta 2AR mRNA levels.
01 Jul 1989
TL;DR: The solution to the grasping problem is based on displacement commands instead of force commands used in robotics and human behavior, which allows a realistic envelope deformation of the human fingers comparable to existing methods.
Abstract: This paper addresses the problem of simulating deformations between objects and the hand of a synthetic character during a grasping process. A numerical method based on finite element theory allows us to take into account the active forces of the fingers on the object and the reactive forces of the object on the fingers. The method improves control of synthetic human behavior in a task level animation system because it provides information about the environment of a synthetic human and so can be compared to the sense of touch. Finite element theory currently used in engineering seems one of the best approaches for modeling both elastic and plastic deformation of objects, as well as shocks with or without penetration between deformable objects. We show that intrinsic properties of the method based on composition/decomposition of elements have an impact in computer animation. We also state that the use of the same method for modeling both objects and human bodies improves the modeling both objects and human bodies improves the modeling of the contacts between them. Moreover, it allows a realistic envelope deformation of the human fingers comparable to existing methods. To show what we can expect from the method, we apply it to the grasping and pressing of a ball. Our solution to the grasping problem is based on displacement commands instead of force commands used in robotics and human behavior.
TL;DR: The Duplan strain of murine leukaemia virus is studied, which induces a severe immunodeficiency disease with striking similarities to human AIDS, and the aetiological agent is identified as another defective retrovirus, with a genome of 4.8 kilobases.
Abstract: DIFFERENT classes of retroviruses have been shown to induce immunodeficiency diseases in various animal species1. These animal models may provide an insight into our understanding of AIDS1–3 but, with the exception of one strain of feline leukaemia virus4, the determinants of pathogenicity have not yet been mapped to these viral genomes. The immunodeficiency-inducing feline leukaemia virus is replication-defective4, harbouring the determinant of pathogenicity within its env sequences5. We have studied the Duplan strain of murine leukaemia virus6 which induces, in C57BL/6 mice7–11, a severe immunodeficiency disease with striking similarities to human AIDS2,3,8,9. We have identified the aetiological agent of this murine immunodeficiency disease as another defective retrovirus, with a genome of 4.8 kilobases. Molecular cloning and sequencing of this DNA showed that the pol and env genes have been deleted, but that the complete gag region has been conserved and has a novel sequence encoding the p12 protein. As with the feline leukaemia virus4,5, these results provide evidence for the role of defective retroviruses in inducing immunodeficiency and facilitate the study of the mechanisms underlying the pathogenesis of retrovirus-induced immunodeficiency syndromes, including AIDS.
TL;DR: The discussion includes the important role that alterations in the physiology of motor units, notably changes in firing rates and muscle fiber atrophy, play in the manifestation of muscle weakness.
Abstract: Clinical and experimental results are reviewed concerning muscle weakness in patients with hemiparesis after a stroke. The discussion includes the important role that alterations in the physiology of motor units, notably changes in firing rates and muscle fiber atrophy, play in the manifestation of muscle weakness. This role is compared with the lesser role that spasticity (defined as hyperactive stretch reflexes) of the antagonist muscle group appears to play in determining the weakness of agonist muscles. The contribution of other factors that result in mechanical restraint of the agonist by the antagonist (e.g., passive mechanical properties and inappropriate cocontraction) is discussed relative to muscle weakness in patients with hemiparesis.
Journal Article•
TL;DR: It was concluded that the 20 m shuttle run is a valid test to predict VO2max in adults and the regression equation retained to ensure a smooth transition between children and adults in predictingVO2max.
Abstract: The purpose of this study was to assess the validity of the 1 min stage version of the 20 m shuttle run multistage test to predict VO2max in adults (53 males and 24 females, 19 to 47 years old). The maximal shuttle run speed (S-MAS) was thus compared to the VO2max attained during a multistage treadmill test (TE-VO2max), the retroextrapolated VO2max at time zero of the O2 recovery curve of the shuttle run (SR-VO2max) and the VO2max predicted from a previously developed regression equation with children (Mercier et al., 1983) and putting 18 year olds in the regression equation for all adults which yielded (SP-VO2max = -27.4 + 6.0 S-MAS). The latter regression equation was very similar to the ones obtained with the two other criteria and was thus retained to ensure a smooth transition between children and adults in predicting VO2max. Correlations and standard errors of the estimate between S-MAS and TE-VO2max (r = 0.90 and Syx = 4.4) or SR-VO2max (r = 0.87 and Syx = 4.7) were quite good. TE-, SR- and SP-VO2max were also similar (mean +/- SD = 49.4 +/- 10.1, 48.8 +/- 9.3 and 47.1 +/- 8.3 mL.kg-1.min-1, respectively, p greater than 0.05). It was concluded that the 20 m shuttle run is a valid test to predict VO2max in adults.
TL;DR: An empirical model relating human running performance to some characteristics of metabolic energy-yielding processes using A, the capacity of anaerobic metabolism, MAP, the maximal aerobic power, and E, the reduction in peak aerobic power with the natural logarithm of race duration T is developed.
Abstract: The objective of this study was to develop an empirical model relating human running performance to some characteristics of metabolic energy-yielding processes using A, the capacity of anaerobic metabolism (J/kg); MAP, the maximal aerobic power (W/kg); and E, the reduction in peak aerobic power with the natural logarithm of race duration T, when T greater than TMAP = 420 s. Accordingly, the model developed describes the average power output PT (W/kg) sustained over any T as PT = [S/T(1 - e-T/k2)] + 1/T integral of T O [BMR + B(1 - e-t/k1)]dt where S = A and B = MAP - BMR (basal metabolic rate) when T less than TMAP; and S = A + [Af ln(T/TMAP)] and B = (MAP - BMR) + [E ln(T/TMAP)] when T greater than TMAP; k1 = 30 s and k2 = 20 s are time constants describing the kinetics of aerobic and anaerobic metabolism, respectively, at the beginning of exercise; f is a constant describing the reduction in the amount of energy provided from anaerobic metabolism with increasing T; and t is the time from the onset of the race. This model accurately estimates actual power outputs sustained over a wide range of events, e.g., average absolute error between actual and estimated T for men's 1987 world records from 60 m to the marathon = 0.73%. In addition, satisfactory estimations of the metabolic characteristics of world-class male runners were made as follows: A = 1,658 J/kg; MAP = 83.5 ml O2.kg-1.min-1; 83.5% MAP sustained over the marathon distance. Application of the model to analysis of the evolution of A, MAP, and E, and of the progression of men's and women's world records over the years, is presented.
TL;DR: Results confirm that both visual analogue and verbal descriptor techniques successfully quantify sensory intensity and affective aspects of pain, but that verbal descriptors may provide the more sensitive tool for separating intensity and unpleasantness.
Abstract: Although the multidimensional nature of pain is now well recognized, there are, nevertheless, very few quantitative tests to measure the separate dimensions of pain and little data concerning their relative sensitivity. The present study compares 2 currently available methods, verbal descriptor and visual analogue scales. Eight subjects rated painful and near-painful heat stimuli by using visual analogue scales for intensity or unpleasantness and by choosing the most appropriate phrases from lists of intensity or unpleasantness descriptors. In the intensity dimension, the relationship between perception and stimulus temperature was essentially identical whether calculated from the visual analogue or verbal descriptor scales. However, data derived from the verbal descriptor scales revealed that subjects rated the painful temperatures as relatively more intense than unpleasant; this difference could not be detected using the visual analogue scales. These results confirm that both visual analogue and verbal descriptor techniques successfully quantify sensory intensity and affective aspects of pain, but that verbal descriptors may provide the more sensitive tool for separating intensity and unpleasantness.
TL;DR: Fourteen new capsular types of Streptococcus suis are described and several cross-reactions probably not due to capsular material were detected among different types by using the coagglutination test.
Abstract: Fourteen new capsular types of Streptococcus suis (types 9 to 22) are described. All reference strains are morphologically and biochemically similar to types previously described. Reference strain types 9 to 13, 15, 16, and 22 were isolated from diseased pigs, whereas types 17 to 19 and 21 came from clinically healthy pigs; type 14 was isolated from a human case of meningitis, and type 20 was isolated from a diseased calf. The group T streptococcus of de Moor has been included in the typing system as type 15. Two-way cross-reactions between types 6 and 16 and a one-way cross-reaction between types 2 and 22 have been demonstrated. In addition, several cross-reactions probably not due to capsular material were detected among different types by using the coagglutination test. This test should not be used alone; weak or multiple positive reactions must be confirmed by the capsular reaction test or the capillary precipitation test.
TL;DR: It is suggested that the balance between the production of IL-4 and IFN-gamma may be significantly influenced by the chronological order of activation of their respective gene.
Abstract: rIL-4 inhibits the production of IFN-gamma by PBMC stimulated with mitogens or allogeneic cells. The suppression is observed at the protein and at the mRNA level; it is dose and time dependent, and it is abolished by a neutralizing mAb to IL-4. It is suggested that the balance between the production of IL-4 and IFN-gamma may be significantly influenced by the chronological order of activation of their respective gene.
TL;DR: An attempt is made to classify patients with cervicopharyngeal pain related to the stylohyoid apparatus according to etiology to lead to a global understanding of the causes of such symptomatology and less confusion among the professions in regard to terminology.
TL;DR: It is shown that some single neurons in medial thalamus of alert monkey discriminate changes in the intensity of noxious stimuli that are equal to or below the monkey's own discrimination threshold.
Abstract: Lateral and medial thalamus are traditionally thought to have separate roles in pain processing, with lateral lemniscal regions transmitting discriminative information about location and intensity, while medial nonspecific regions are involved in emotional responses. Contrary to this view, the present study shows that some single neurons in medial thalamus of alert monkey discriminate changes in the intensity of noxious stimuli that are equal to or below the monkey's own discrimination threshold. Since these neurons are also modulated by anesthesia and attentional factors, we suggest that parts of medial thalamus may participate in both discriminative and affective dimensions of pain.
TL;DR: Because upper gastrointestinal series x-ray studies failed to detect upper gastrointestinal lesions in 13 patients of 69 of those with upper gastrointestinal disease, endoscopy should be considered in all children and adolescents in whom a diagnosis of Crohn disease is entertained.
Abstract: This retrospective study of Crohn disease in 230 children and adolescents with a mean age of 12.5 years at the time of diagnosis and an average follow-up of 6.6 years showed that 30% had lesions of the esophagus, stomach, and duodenum. Three patients had Crohn disease isolated to the upper gastrointestinal tract. The 169 patients with both small and large bowel disease were at greater risk (33%, P less than .05) of having upper gastrointestinal lesions than the 37 with isolated small bowel disease and the 21 with disease limited to the colon and/or rectum. An aggregate of symptoms and signs more likely present in those with upper gastrointestinal involvement included: dysphagia, pain when eating, nausea and/or vomiting, and aphthous lesions of the mouth. Furthermore, weight loss was more severe and hypoalbuminemia more frequent. Because upper gastrointestinal series x-ray studies failed to detect upper gastrointestinal lesions in 13 patients of 69 of those with upper gastrointestinal disease, endoscopy should be considered in all children and adolescents in whom a diagnosis of Crohn disease is entertained. Endoscopy and biopsy of the upper gastrointestinal tract should be done in any patient with symptoms suggestive of proximal involvement. Finally, in view of the fact that endoscopy established the diagnosis of Crohn disease in five patients previously thought to have chronic ulcerative colitis, the procedure should routinely be performed in all patients with chronic ulcerative colitis or indeterminate colitis before surgery is performed.
TL;DR: The results of this quantitative synthesis suggest that patients with bleeding esophageal varices benefit from the inclusion of repeated sclerotherapy in their long-term management regimen.
TL;DR: The chemical shift data of the oligomers and the parent polymers were compared, and indicated the distribution of the substituents in hybrid polymers.
TL;DR: The apparatus designed by Charles H .
Abstract: Quantum cryptography has recently entered the experimental era . The first convincingl y successful quantum exchange took place a few weeks ago . After a short historical revie w of quantum cryptography, we report on the apparatus designed by Charles H . Bennett and built by him at the IBM T. J . Watson Research Center in Yorktown Heights, NY, with the help of John Smolin . Our preliminary results follow .
TL;DR: Cutaneous primary afferents were recorded intracellularly during fictive locomotion in decorticated cats with the goal of improving the understanding of how locomotor networks might centrally control the transmission in cutaneous pathways at a presynaptic level.
Abstract: 1. Cutaneous primary afferents were recorded intracellularly during fictive locomotion in decorticated cats with the goal of improving our understanding of how locomotor networks might centrally co...
TL;DR: Histologically, corticosteroids significantly reduced the severity of OA structural changes of the cartilage on both medial and lateral femoral condyles and tibial plateaus in operated animals, with the exception of the lateral plateaus of those treated orally.
Abstract: The in vivo effects of corticosteroids on osteoarthritic (OA) lesions were examined in 12 dogs in which the anterior cruciate ligament had been sectioned Six were treated with oral prednisone and 6 were treated with intraarticular (IA) injections of triamcinolone hexacetonide (TH), at surgery and 4 weeks later Twelve other operated dogs received no treatment All dogs were killed 8 weeks postsurgery Four of 15 normal control dogs received IA TH injections Operated untreated dogs developed significant cartilage lesions on the femoral condyles and tibial plateaus with prominent osteophytes Operated dogs treated orally or with IA injections had a significant reduction in osteophyte size Cartilage erosions on femoral condyles were observed in 25% of the untreated dogs, 8% of the dogs receiving oral prednisone, and none of the dogs receiving IA TH In both groups of treated dogs, the size of the tibial plateau lesions was significantly reduced compared with the operated untreated dogs Histologically, corticosteroids significantly reduced the severity of OA structural changes of the cartilage on both medial and lateral femoral condyles and tibial plateaus in operated animals, with the exception of the lateral plateaus of those treated orally In electron microscopy studies, we found no evidence of increased cell degeneration or death associated with steroids IA corticosteroids had no deleterious effects on normal articular cartilage These results indicate that glucocorticoids administered orally or intraarticularly are effective against the development of OA lesions in this model
TL;DR: This work presents a new algorithm for estimating the fractal dimension of surfaces - the variation method - that is more reliable and robust than the standard ones, and is shown to give more accurate results than the classical algorithms.
Abstract: Fractal objects derive from many interface phenomena, as they arise in, for example, materials science, chemistry and geology. Hence the problem of estimating fractal dimension becomes of both theoretical and practical importance. Existing algorithms implement the standard definitions of fractal dimension directly, but, as we show, often give unreliable results when applied to digitized and quantized data. We present a new algorithm for estimating the fractal dimension of surfaces - the variation method - that is more reliable and robust than the standard ones. It is based on a new definition of fractal dimension particularly suited for graphs of functions. The variation method is validated with both fractional brownian surfaces and Takagi surfaces, two classes of mathematical objects with known fractal dimension, and is shown to give more accurate results than the classical algorithms. Finally, our new algorithm is applied to data from sand-blasted metal surfaces.