Showing papers by "Harvard University published in 1986"

Numerical Recipes in C: The Art of Scientific Computing

Abstract: From the Publisher: This is the revised and greatly expanded Second Edition of the hugely popular Numerical Recipes: The Art of Scientific Computing. The product of a unique collaboration among four leading scientists in academic research and industry, Numerical Recipes is a complete text and reference book on scientific computing. In a self-contained manner it proceeds from mathematical and theoretical considerations to actual practical computer routines. With over 100 new routines (now well over 300 in all), plus upgraded versions of many of the original routines, this book is more than ever the most practical, comprehensive handbook of scientific computing available today. The book retains the informal, easy-to-read style that made the first edition so popular, with many new topics presented at the same accessible level. In addition, some sections of more advanced material have been introduced, set off in small type from the main body of the text. Numerical Recipes is an ideal textbook for scientists and engineers and an indispensable reference for anyone who works in scientific computing. Highlights of the new material include a new chapter on integral equations and inverse methods; multigrid methods for solving partial differential equations; improved random number routines; wavelet transforms; the statistical bootstrap method; a new chapter on "less-numerical" algorithms including compression coding and arbitrary precision arithmetic; band diagonal linear systems; linear algebra on sparse matrices; Cholesky and QR decomposition; calculation of numerical derivatives; Pade approximants, and rational Chebyshev approximation; new special functions; Monte Carlo integration in high-dimensional spaces; globally convergent methods for sets of nonlinear equations; an expanded chapter on fast Fourier methods; spectral analysis on unevenly sampled data; Savitzky-Golay smoothing filters; and two-dimensional Kolmogorov-Smirnoff tests. All this is in addition to material on such basic top

Development of criteria for the classification and reporting of osteoarthritis: Classification of osteoarthritis of the knee

Abstract: For the purposes of classification, it should be specified whether osteoarthritis (OA) of the knee is of unknown origin (idiopathic, primary) or is related to a known medical condition or event (secondary). Clinical criteria for the classification of idiopathic OA of the knee were developed through a multicenter study group. Comparison diagnoses included rheumatoid arthritis and other painful conditions of the knee, exclusive of referred or para-articular pain. Variables from the medical history, physical examination, laboratory tests, and radiographs were used to develop sets of criteria that serve different investigative purposes. In contrast to prior criteria, these proposed criteria utilize classification trees, or algorithms.

Dynamic Scaling of Growing Interfaces

Abstract: A model is proposed for the evolution of the profile of a growing interface. The deterministic growth is solved exactly, and exhibits nontrivial relaxation patterns. The stochastic version is studied by dynamic renormalization-group techniques and by mappings to Burgers's equation and to a random directed-polymer problem. The exact dynamic scaling form obtained for a one-dimensional interface is in excellent agreement with previous numerical simulations. Predictions are made for more dimensions.

A human DNA segment with properties of the gene that predisposes to retinoblastoma and osteosarcoma

Abstract: The genomes of various tumour cells contain mutant oncogenes that act dominantly, in that their effects can be observed when they are introduced into non-malignant cells. There is evidence for another class of oncogenes, in which tumour-predisposing mutations are recessive to wild-type alleles. Retinoblastoma is a prototype biological model for the study of such recessive oncogenes. This malignant tumour, which arises in the eyes of children, can be explained as the result of two distinct genetic changes, each causing loss of function of one of the two homologous copies at a single genetic locus, Rb, assigned to the q14 band of human chromosome 13. Mutations affecting this locus may be inherited from a parent, may arise during gametogenesis or may occur somatically. Those who inherit a mutant allele at this locus have a high incidence of non-ocular, second tumours, almost half of which are osteosarcomas believed to be caused by the same mutation. Here we describe the isolation of a complementary DNA segment that detects a chromosomal segment having the properties of the gene at this locus. The gene is expressed in many tumour types, but no RNA transcript has been found in retinoblastomas and osteosarcomas. The cDNA fragment detects a locus spanning at least 70 kilobases (kb) in human chromosome band 13q14, all or part of which is frequently deleted in retinoblastomas and osteosarcomas.

Total energy intake: implications for epidemiologic analyses

Abstract: Associations between intake of specific nutrients and disease cannot be considered primary effects of diet if they are simply the result of differences between cases and noncases in body size, physical activity, and metabolic efficiency. Epidemiologic studies of diet and disease should therefore be directed at the effect of nutrient intakes independent of total caloric intake in most instances. This is not accomplished with nutrient density measures of dietary intake but can be achieved by employing nutrient intakes adjusted for caloric intake by regression analysis. While pitfalls in the manipulation and interpretation of energy intake data in epidemiologic studies have been emphasized, these considerations also highlight the usefulness of obtaining a measurement of total caloric intake. For instance, if a questionnaire obtained information on only cholesterol intake in a study of coronary heart disease, it is possible that no association with disease would be found even if a real positive effect of a high cholesterol diet existed, since the caloric intake of cases is likely to be less than that of noncases. Such a finding could be appropriately interpreted if an estimate of total caloric intake were available. The relationships between dietary factors and disease are complex. Even with carefully collected measures of intake, consideration of the biologic implications of various analytic approaches is needed to avoid misleading conclusions.

Origin of life: The RNA world

Abstract: Sur la base de la decouverte d'activites enzymatiques de certains ARN (chez E. coli au cours de la maturation des ARN+ et chez Tetrahymena avec un exon d'un ARNr a auto-epissage), l'auteur postule un systeme, auto-replicatif a l'origine uniquement compose de molecules d'ARN

The botany of mangroves

Abstract: Preface Acknowledgements Part I. General Account: 1. Ecology 2. Floristics 3. Biogeography 4. Shoot systems 5. Root systems 6. Water relations and salt balance 7. Flowering 8. Seedlings and seeds 9. Utilization and exploitation Part II. Detailed Descriptions by Family References Index.

Cointegration and Tests of Present Value Models

Abstract: In a model where a variable Y[sub t] is proportional to the present value, with constant discount rate, of expected future values of a variable y[sub t] the "spread" S[sub t]= Y[sub t] - [theta sub t] will be stationary for some [theta] whether or not y[sub t]must be differenced to induce stationarity. Thus, Y[sub t] and y[sub t] are cointegrated. The model implies that S[sub t] is proportional to the optimal forecast of [delta Y{sub t+1}] and also to the optimal forecast of S*[sub t], the present value of future [delta y{sub t}]. We use vector autoregressive methods, and recent literature on cointegrated processes, to test the model. When Y[sub t] is the long-term interest rate and y[sub t] the short-term interest rate, we find in postwar U.S. data that S[sub t] behaves much like an optimal forecast of S*[sub t] even though as earlier research has shown it is negatively correlated with [delta Y{sub t+1}]. When Y[sub t] is a real stock price index and y[sub t] the corresponding real dividend, using annual U.S. data for 1871-1986 we obtain less encouraging results for the model, al-though the results are sensitive to the assumed discount rate.

Hysteresis and the European Unemployment Problem

Abstract: European unemployment has been steadily increasing for the last 15 years and isexpected to remain very high for many years to come. In this paper, we argue thatthis fact implies that shocks have much more persistent effects on unemployment thanstandard theories can possibly explain. We develop a theory which can explain suchpersistence, and which is based on the distinction between insiders and outsiders inwage bargaining. We argue that if wages are largely set by bargaining betweeninsiders and firms, shocks which affect actual unemployment tend also to affectequilibrium unemployment. We then confront the theory to both the detailed facts ofthe European situation as well as to earlier periods of high persistent unemploymentsuch as the Great Depression in the US.

The etiology of osteoarthritis of the hip: an integrated mechanical concept.

Abstract: More than 90% of patients with so-called primary or idiopathic osteoarthritis of the hips in whom sufficient data were available to make an assessment of the normality of the hip joint at the cessation of growth clearly showed demonstrable abnormalities in the hip joint. The most common are mild acetabular dysplasia and/or pistol grip deformity. This latter deformity is associated with mild slipped capital femoral epiphysis (recognized or unrecognized at the time), Legg-Perthes' disease (recognized or unrecognized at the time), multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia, and/or the presence of an intraacetabular labrum, as well as, in certain instances, acetabular dysplasia. When these abnormalities are taken in conjunction with the detection of other metabolic abnormalities that can lead to osteoarthritis of the hip and which may not be recognized readily, such as hemochromatosis, ochronosis, calcium pyrophosphate disease, and monarticular rheumatoid arthritis, it seems clear that either osteoarthritis of the hip does not exist at all as a primary disease entity or, if it does, is extraordinarily rare.

Menu Auctions, Resource Allocation, and Economic Influence

Abstract: In many examples of competitive bidding (e.g., government construction contracting) the relevant object is either partially divisible or ill-defined, in contrast to much of the recent theoretical work on auctions. In this paper we consider a more general class of auctions, in which bidders name a "menu" of offers for various possible actions (allocations) available to the auctioneer. We focus upon "first-price" menu auctions under the assumption of complete information, and show that, for an attractive refinement of the set of Nash Equilibria, an efficient action always results. Our model also has application to situations of economic influence, in which interested parties independently attempt to influence a decision-maker's action.

Replication of the neurochemical characteristics of Huntington's disease by quinolinic acid

Abstract: Huntington's disease (HD) is an autosomal dominant neurological disorder characterized by progressive chorea, cognitive impairment and emotional disturbance. The disease usually occurs in midlife and symptoms progress inexorably to mental and physical incapacitation. It has been postulated that an excitotoxin is involved in the pathogenesis of HD. Schwarcz and colleagues have shown that quinolinic acid (QA) can produce axon-sparing lesions similar to those observed in HD. The lesions result in a depletion of neurotransmitters contained within striatal spiny neurones, for example gamma-aminobutyric acid (GABA), while dopamine is unaffected. Recently, we and others have demonstrated that in HD striatum there is a paradoxical 3-5-fold increase in both somatostatin and neuropeptide Y which is attributable to selective preservation of a subclass of striatal aspiny neurones in which these peptides are co-localized. In the present study we demonstrate that lesions due to quinolinic acid closely resemble those of HD as they result in marked depletions of both GABA and substance P, with selective sparing of somatostatin/neuropeptide Y neurones. Lesions produced by kainic acid (KA), ibotenic acid (IA) and N-methyl-D-aspartate (MeAsp) were unlike those produced by QA, as they affected all cell types without sparing somatostatin/neuropeptide Y neurones. These results suggest that QA or a similar compound could be responsible for neuronal degeneration in HD.

The Developmental Niche: A Conceptualization at the Interface of Child and Culture:

Abstract: Anthropological approaches to human development have been oriented primarily to the socialized adult, at the expense of understanding developmental processes. Developmental psychology, in contrast, has traditionally been concerned with a decontextualized, 'universal' child. After a brief historical review, the 'developmental niche' is introduced as a framework for examining the cultural structuring of child development. The developmental niche has three components: the physical and social settings in which the child lives; the customs of child care and child rearing; and the psychology of the caretakers. Homeostatic mechanisms tend to keep the three subsystems in harmony with each other and appropriate to the developmental level and individual characteristics of the child. Nevertheless, they have different relationships to other features of the larger environment and thus constitute somewhat independent routes of disequilibrium and change. Regularities within and among the subsystems, and thematic continu...

Prevention of diabetic glomerulopathy by pharmacological amelioration of glomerular capillary hypertension.

Abstract: Two groups of adult male Munich-Wistar rats and a third group of nondiabetic age-matched and weight-matched normal control rats underwent micropuncture study 1 mo, and morphologic studies 14 mo, after induction of streptozotocin diabetes or sham treatment. All animals were fed standard rat chow. Diabetic rats received daily ultralente insulin to maintain stable moderate hyperglycemia (approximately 350 mg/dl). In addition, one group of diabetic rats was treated with the angiotensin I converting enzyme inhibitor, enalapril, 15 mg/liter of drinking water. Average kidney weight, whole kidney and single-nephron glomerular filtration rate, and glomerular plasma flow rate were elevated to similar values in both groups of diabetic rats, relative to normal control rats. Non-enalapril-treated diabetic rats exhibited significant elevations in mean glomerular capillary hydraulic pressure and transcapillary hydraulic pressure gradient, compared with the other groups studied, and only this group eventually developed marked and progressive albuminuria. Likewise, histological examination of the kidneys at 14 mo disclosed a high incidence of glomerular structural abnormalities only in non-enalapril-treated diabetic rats. These findings indicate that prevention of glomerular capillary hypertension in rats with diabetes mellitus effectively protects against the subsequent development of glomerular structural injury and proteinuria. This protection is afforded despite pronounced hyperglycemia and elevated levels of glucosylated hemoglobin, further supporting our view that hemodynamic rather than metabolic factors predominate in the pathogenesis of diabetic glomerulopathy.

The Existence of Equilibrium in Discontinuous Economic Games, I: Theory

Abstract: The article presents information about the existence of equilibrium in discontinuous economic games. In this paper and its sequel presents study the existence of Nash equilibrium in games where agents' payoff functions are discontinuous. The enquiry is motivated by a number of recent studies that have uncovered serious existence problems in seemingly innocuous economic games. In the sequel to this paper, authors have explained the utility function in the economic games referred to earlier are neither continuous nor quasi-concave. However, they demonstrate that the payoff functions in mildly modified versions of these constructs exhibit two weaker forms of continuity which, together with the requirement of quasi-concavity, suffice for the existence of an equilibrium. From this one may conclude that, at least in the modified versions of these models, discontinuities in the payoff functions are not the real source of the problem. Rather, it is the failure of the payoff functions to the quasi-concave which is "responsible" for the non-existence of equilibrium. These observations bear on the existence of Nash equilibrium in pure strategies.

Therapeutic advantage of converting enzyme inhibitors in arresting progressive renal disease associated with systemic hypertension in the rat.

Abstract: Micropuncture and morphologic studies were performed in six groups of male Munich-Wistar rats after removal of the right kidney and segmental infarction of two-thirds of the left kidney. Groups 1 and 4 received no specific therapy. Groups 2 and 5 were treated with the angiotensin I-converting enzyme inhibitor, enalapril, 50 mg/liter, in the drinking water. Groups 3 and 6 were treated with reserpine (5 mg/liter), hydralazine (80 mg/liter), and hydrochlorothiazide (25 mg/liter). All rats were fed standard chow. Groups 1-3 underwent micropuncture study 4 wk after renal ablation. Untreated group 1 rats exhibited systemic hypertension and elevation of the single nephron glomerular filtration rate (SNGFR) due to high average values for the mean glomerular transcapillary hydraulic pressure gradient (delta P) and glomerular plasma flow rate (QA). In group 2 rats, treatment with enalapril prevented systemic hypertension and maintained delta P at near-normal levels without significant reduction in SNGFR and QA. In contrast, triple drug therapy normalized systemic hypertension, but failed to lower delta P in group 3 rats. Groups 4-6 were followed for 12 wk after renal ablation. Untreated group 4 rats demonstrated continuous systemic hypertension, progressive proteinuria, and glomerular structural lesions, including mesangial expansion and frequent areas of segmental sclerosis. In group 5 rats, treatment with enalapril maintained systemic blood pressure at normal levels over the 12-wk period and dramatically limited the development of proteinuria and glomerular lesions. Despite equivalent systemic blood pressure control in group 6 rats, failure of triple drug therapy to control glomerular hypertension was associated with progressive proteinuria and glomerular lesions comparable to those seen in untreated group 4 rats. Thus, unless glomerular capillary hypertension is corrected, control of systemic blood pressure is insufficient to prevent progressive renal injury in rats with reduced renal mass.

Matrix fracture in fiber-reinforced ceramics

Abstract: A fiber-reinforced ceramic subject to tensile stress in the fiber direction can undergo extensive matrix cracking normal to the fibers, while the fibers remain intact. In this paper, the critical conditions for the onset of widespread matrix cracking are studied analytically on the basis of fracture mechanics theory. Two distinct situations concerning the fiber-matrix interface are contemplated : (i) unbonded fibers initially held in the matrix by thermal or other strain mismatches, but susceptible to frictional slip, and (ii) fibers that initially are weakly bonded to the matrix, but may be debonded by the stresses near the tip of an advancing matrix crack. The results generalize those of the Aveston-Cooper-Kelly theory for case (i). Optimal thermal strain mismatches for maximum cracking strength are studied, and theoretical results are compared with experimental data for a SiC fiber, lithium-alumina-silicate glass matrix composite.

Validation of questionnaire information on risk factors and disease outcomes in a prospective cohort study of women

Abstract: To assess the validity of self-reported illnesses, medical records were reviewed for participants reporting major illnesses on the biennial follow-up questionnaires used in a prospective cohort study which began in 1976. In over 90% of cases of cancer of the breast, skin, large bowel, and thyroid, histopathology reports confirmed the subjects' self-report. Lower levels of confirmation were obtained for cancers of the lung, ovary, and uterus. Application of strict diagnostic criteria also gave lower levels of confirmation for myocardial infarction (68%) and stroke (66%). Among random samples of women reporting fractures and hypertension all records obtained confirmed self-reports. For self-reported elevated cholesterol levels 85.7% of self-reports were confirmed. Self-report is a valuable epidemiologic tool but may require additional documentation when the disease is diagnostically complex.

Isolation of candidate cDNAs for portions of the Duchenne muscular dystrophy gene

Abstract: Duchenne muscular dystrophy (DMD) and the less severe Becker muscular dystrophy (BMD) are human X-linked muscle-wasting disorders that have been localized to the band Xp21 by genetic linkage analysis1–9 and cytologically detectable abnormalities10–12. A cloned DNA segment, DXS164 (or pERT87), has been shown to detect deletions in the DNA of unrelated DMD and BMD males13–15. Here we present the nucleotide sequence of two highly conserved DNA fragments from the DXS164 locus and their homologous sequences from the mouse X chromosome. One of the human conserved segments hybridized to a large transcript in RNA isolated from human fetal skeletal muscle and was used to isolate cDNA clones which cover approximately 10% of this transcript. The cDNA clones map to Xp21 and hybridize with a minimum of eight small regions that span 130 kilobases (kb) of the DXS164 locus. These expressed sequences are candidates for portions of the gene responsible for both DMD and BMD.

The Dividend-Price Ratio and Expectations of Future Dividends and Discount Factors

Abstract: A linearization of a rational expectations present value model for corporate stock prices produces a simple relation between the log dividend-price ratio and mathematical expectations of future log real dividend changes and future real discount rates. This relation can be tested using vector autoregressive methods. Three versions of the linearized model, differing in the measure of discount rates, are tested for U. S. time series 1871-1986: versions using real interest rate data, aggregate real consumption data, and return variance data. The results yield a metric to judge the relative importance of real dividend growth, measured real discount rates and unexplained factors in determining the dividend-price ratio.

Identification of a putative second T-cell receptor.

Abstract: Framework monoclonal antibodies have identified a population of human lymphocytes that express the T3 glycoprotein but not the T-cell receptor (TCR) alpha- and beta-subunits. Chemical crosslinking experiments reveal that these lymphocytes express novel T3-associated polypeptides, one of which appears to be the product of the T gamma gene. The other polypeptide may represent a fourth TCR subunit, designated T delta.