Showing papers by "Harvard University published in 1991"
TL;DR: OCT as discussed by the authors uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way analogous to ultrasonic pulse-echo imaging.
Abstract: A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.
11,568 citations
TL;DR: A revision of the FTQ: the Fagerström Test for Nicotine Dependence (FTND), which found that a revised scoring of time to the first cigarette of the day (TTF) and number of cigarettes smoked per day (CPD) improved the scale.
Abstract: We examine and refine the Fagerstrom Tolerance Questionnaire (FTQ: Fagerstrom, 1978). The relation between each FTQ item and biochemical measures of heaviness of smoking was examined in 254 smokers. We found that the nicotine rating item and the inhalation item were unrelated to any of our biochemical measures and these two items were primary contributors to psychometric deficiencies in the FTQ. We also found that a revised scoring of time to the first cigarette of the day (TTF) and number of cigarettes smoked per day (CPD) improved the scale. We present a revision of the FTQ: the Fagerstrom Test for Nicotine Dependence (FTND).
9,766 citations
TL;DR: For 98 countries in the period 1960-1985, the growth rate of real per capita GDP is positively related to initial human capital (proxied by 1960 school-enrollment rates) and negatively related to the initial (1960) level as mentioned in this paper.
Abstract: For 98 countries in the period 1960–1985, the growth rate of real per capita GDP is positively related to initial human capital (proxied by 1960 school-enrollment rates) and negatively related to the initial (1960) level of real per capita GDP. Countries with higher human capital also have lower fertility rates and higher ratios of physical investment to GDP. Growth is inversely related to the share of government consumption in GDP, but insignificantly related to the share of public investment. Growth rates are positively related to measures of political stability and inversely related to a proxy for market distortions.
9,420 citations
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TL;DR: In this paper, the authors used a new data set on the growth of large industries in 170 U.S. cities between 1956 and 1987 and found that local competition and urban variety, but not regional specialization, encourage employment growth in industries.
Abstract: Recent theories of economic growth, including Romer (1986), Porter (1989) and Jacobs (1969), have stressed the role of technological spillovers in generating growth. Because such knowledge spillovers are particularly effective in cities, where communication between people is more extensive, data on the growth of industries in different cities allows us to test some of these theories. Using a new data set on the growth of large industries in 170 U.S. cities between 1956 and 1987, we find that local competition and urban variety, but not regional specialization, encourage employment growth in industries. The evidence suggests that important knowledge spillovers might be between, rather than within industries, consistent with the theories of Jacobs (1969).
4,223 citations
TL;DR: The updated information on tolerance of normal tissues of concern in the protocols of this contract, based on available data, is presented, with a special emphasis on partial volume effects.
Abstract: The importance of knowledge on tolerance of normal tissue organs to irradiation by radiation oncologists cannot be overemphasized. Unfortunately, current knowledge is less than adequate. With the increasing use of 3-D treatment planning and dose delivery, this issue, particularly volumetric information, will become even more critical. As a part of the NCI contract N01 CM-47316, a task force, chaired by the primary author, was formed and an extensive literature search was carried out to address this issue. In this issue. In this manuscript we present the updated information on tolerance of normal tissues of concern in the protocols of this contract, based on available data, with a special emphasis on partial volume effects. Due to a lack of precise and comprehensive data base, opinions and experience of the clinicians from four universities involved in the contract have also been contributory. Obviously, this is not and cannot be a comprehensive work, which is beyond the scope of this contract.
4,133 citations
TL;DR: The results suggest that calcineurin is involved in a common step associated with T cell receptor and IgE receptor signaling pathways and that cyclophilin and FKBP mediate the actions of CsA and Fk506 by forming drug-dependent complexes with and altering the activity of calcineURin-calmodulin.
3,968 citations
TL;DR: In this article, the authors describe the mixed mode cracking in layered materials and elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness, showing that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip.
Abstract: Publisher Summary This chapter describes the mixed mode cracking in layered materials. There is ample experimental evidence that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip. An unloaded crack subsequently subject to a combination of modes I and II will initiate growth by kinking in such a direction that the advancing tip is in mode I. The chapter also elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness. The competition between crack advance within the interface and kinking out of the interface depends on the relative toughness of the interface to that of the adjoining material. The interface stress intensity factors play precisely the same role as their counterparts in elastic fracture mechanics for homogeneous, isotropic solids. When an interface between a bimaterial system is actually a very thin layer of a third phase, the details of the cracking morphology in the thin interface layer can also play a role in determining the mixed mode toughness. The elasticity solutions for cracks in multilayers are also elaborated.
3,828 citations
TL;DR: The cross-sectional problem is logically prior to a consideration of dynamics, and better understood, and three promising streams of research that address the longitudinal problem still fall short of exposing the true origins of competitive success.
Abstract: This paper reviews the progress of the strategy field towards developing a truly dynamic theory of strategy. It separates the theory of strategy into the causes of superior performance at a given period in time (termed the cross-sectional problem) and the dynamic process by which competitive positions are created (termed the longitudinal problem). The cross-sectional problem is logically prior to a consideration of dynamics, and better understood. The paper then reviews three promising streams of research that address the longitudinal problem. These still fall short of exposing the true origins of competitive success. One important category of these origins, the local environment in which a firm is based, is described. Many questions remain unanswered, however, and the paper concludes with challenges for future research.
3,780 citations
TL;DR: The high proportion that are due to management errors suggests that many others are potentially preventable now, and reducing the incidence of these events will require identifying their causes and developing methods to prevent error or reduce its effects.
Abstract: Background In a sample of 30,195 randomly selected hospital records, we identified 1133 patients (3.7 percent) with disabling injuries caused by medical treatment. We report here an analysis of these adverse events and their relation to error, negligence, and disability. Methods Two physician-reviewers independently identified the adverse events and evaluated them with respect to negligence, errors in management, and extent of disability. One of the authors classified each event according to type of injury. We tested the significance of differences in rates of negligence and disability among categories with at least 30 adverse events. Results Drug complications were the most common type of adverse event (19 percent), followed by wound infections (14 percent) and technical complications (13 percent). Nearly half the adverse events (48 percent) were associated with an operation. Adverse events during surgery were less likely to be caused by negligence (17 percent) than nonsurgical ones (37 percent). The proportion of adverse events due to negligence was highest for diagnostic mishaps (75 percent), noninvasive therapeutic mishaps ("errors of omission") (77 percent), and events occurring in the emergency room (70 percent). Errors in management were identified for 58 percent of the adverse events, among which nearly half were attributed to negligence. Conclusions Although the prevention of many adverse events must await improvements in medical knowledge, the high proportion that are due to management errors suggests that many others are potentially preventable now. Reducing the incidence of these events will require identifying their causes and developing methods to prevent error or reduce its effects.
3,734 citations
Book•
06 Feb 1991TL;DR: The Power of Reframing as mentioned in this paper is the power of reframing to make sense of the organization and its members, and it can be found in the following three main directions: the human resource frame in action, the human resources frame, and the political frame.
Abstract: MAKING SENSE OF ORGANIZATIONS. Introduction: The Power of Reframing. Simple Ideas, Complex Organizations. THE STRUCTURAL FRAME. Getting Organized. Structuring and Restructuring. Organizing Groups and Teams. THE HUMAN RESOURCE FRAME. People and Organizations. Human Resource Frame in Action. Groups and Interpersonal. THE POLITICAL FRAME. Power, Conflict, and Coalitions. The Manager as Politician. Organizations as Political Arenas and Political Agents. THE SYMBOLIC FRAME. Organizational Culture and Symbols. The Organization as Theater. Organizational Culture in Action. IMPROVING LEADERSHIP PRACTICE. Integrating Frames for Effective Practice. Reframing in Action: The Power of Scenarios. Choosing a Frame. Reframing Change: Training and Alignment. Reframing Leadership. Leaders as Architects and Catalysts. Leaders as Advocates and Prophets. Epilogue: Artistry, Choice, and Leadership.
3,638 citations
TL;DR: These examinations in CHS permit evaluation of CVD risk factors in older adults, particularly in groups previously under-represented in epidemiologic studies, such as women and the very old.
University of Texas Health Science Center at Houston1, Virginia Commonwealth University2, Stony Brook University3, University of California, Los Angeles4, University of Pittsburgh5, University of Pennsylvania6, New York University7, University of Colorado Denver8, University of Illinois at Chicago9, Harvard University10, National Institutes of Health11, Cleveland Clinic12
TL;DR: Mortality was most closely associated with right ventricular hemodynamic function and can be characterized by means of an equation using three variables: mean pulmonary artery pressure, mean right atrial pressure, and cardiac index.
Abstract: Objective To characterize mortality in persons diagnosed with primary pulmonary hypertension and to investigate factors associated with survival. Design Registry with prospective follow-up. Setting Thirty-two clinical centers in the United States participating in the Patient Registry for the Characterization of Primary Pulmonary Hypertension supported by the National Heart, Lung, and Blood Institute. Patients Patients (194) diagnosed at clinical centers between 1 July 1981 and 31 December 1985 and followed through 8 August 1988. Measurements At diagnosis, measurements of hemodynamic variables, pulmonary function, and gas exchange variables were taken in addition to information on demographic variables, medical history, and life-style. Patients were followed for survival at 6-month intervals. Main results The estimated median survival of these patients was 2.8 years (95% Cl, 1.9 to 3.7 years). Estimated single-year survival rates were as follows: at 1 year, 68% (Cl, 61% to 75%); at 3 years, 48% (Cl, 41% to 55%); and at 5 years, 34% (Cl, 24% to 44%). Variables associated with poor survival included a New York Heart Association (NYHA) functional class of III or IV, presence of Raynaud phenomenon, elevated mean right atrial pressure, elevated mean pulmonary artery pressure, decreased cardiac index, and decreased diffusing capacity for carbon monoxide (DLCO). Drug therapy at entry or discharge was not associated with survival duration. Conclusions Mortality was most closely associated with right ventricular hemodynamic function and can be characterized by means of an equation using three variables: mean pulmonary artery pressure, mean right atrial pressure, and cardiac index. Such an equation, once validated prospectively, could be used as an adjunct in planning treatment strategies and allocating medical resources.
TL;DR: The ability to prepare structures in the upper part of this range of sizes would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.
Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.
TL;DR: A dominant behavioral marker, rol‐6(su‐1006), and an efficient microinjection procedure which facilitate the recovery of Caenorhabditis elegans transformants are described and it is shown that low copy number extrachromosomal transformation can be achieved by adjusting the relative concentration of DNA molecules in the injection mixture.
Abstract: We describe a dominant behavioral marker, rol-6(su-1006), and an efficient microinjection procedure which facilitate the recovery of Caenorhabditis elegans transformants. We use these tools to study the mechanism of C.elegans DNA transformation. By injecting mixtures of genetically marked DNA molecules, we show that large extrachromosomal arrays assemble directly from the injected molecules and that homologous recombination drives array assembly. Appropriately placed double-strand breaks stimulated homologous recombination during array formation. Our data indicate that the size of the assembled transgenic structures determines whether or not they will be maintained extrachromosomally or lost. We show that low copy number extrachromosomal transformation can be achieved by adjusting the relative concentration of DNA molecules in the injection mixture. Integration of the injected DNA, though relatively rare, was reproducibly achieved when single-stranded oligonucleotide was co-injected with the double-stranded DNA.
01 Dec 1991
TL;DR: In this article, self-assembly is defined as the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds.
Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.
TL;DR: This paper found that the season of birth is related to educational attainment and earnings, and that roughly 25 percent of potential dropouts remain in school because of compulsory schooling laws. But, they did not study the effect of compulsory attendance laws on educational attainment.
Abstract: We establish that season of birth is related to educational attainment because of school start age policy and compulsory school attendance laws. Individuals born in the beginning of the year start school at an older age, and can therefore drop out after completing less schooling than individuals born near the end of the year. Roughly 25 percent of potential dropouts remain in school because of compulsory schooling laws. We estimate the impact of compulsory schooling on earnings by using quarter of birth as an instrument for education. The instrumental variables estimate of the return to education is close to the ordinary least squares estimate, suggesting that there is little bias in conventional estimates. Every developed country in the world has a compulsory schooling requirement, yet little is known about the effect these laws have on educational attainment and earnings.1 This paper exploits an unusual natural experiment to estimate the impact of compulsory schooling laws in the United States. The experiment stems from the fact that children born in different months of the year start school at different ages, while compulsory schooling laws generally require students to remain in school until their sixteenth or seventeenth birthday. In effect, the interaction of school-entry requirements and compulsory schooling laws compel students born
TL;DR: It is demonstrated that free heparin and heparan sulfate can reconstitute a low affinity receptor that is, in turn, required for the high affinity binding of bFGF.
TL;DR: Rolling of leukocytes on vascular endothelial cells, an early event in inflammation, can be reproduced in vitro on artificial lipid bilayers containing purified CD62, a selectin also named PADGEM and GMP-140 that is inducible on endothelial Cells.
TL;DR: It is proposed that binge eating is motivated by a desire to escape from self-awareness, and the escape model is capable of integrating much of the available evidence about binge eating.
Abstract: This article proposes that binge eating is motivated by a desire to escape from self-awareness. Binge eaters suffer from high standards and expectations, especially an acute sensitivity to the difficult (perceived) demands of others. When they fall short of these standards, they develop an aversive pattern of high self-awareness, characterized by unflattering views of self and concern over how they are perceived by others. These aversive self-perceptions are accompanied by emotional distress, which often includes anxiety and depression. To escape from this unpleasant state, binge eaters attempt the cognitive response of narrowing attention to the immediate stimulus environment and avoiding broadly meaningful thought. This narrowing of attention disengages normal inhibitions against eating and fosters an uncritical acceptance of irrational beliefs and thoughts. The escape model is capable of integrating much of the available evidence about binge eating.
TL;DR: A case-control design involving only cases may be used when brief exposure causes a transient change in risk of a rare acute-onset disease and self-matching of cases eliminates the threat of control-selection bias and increases efficiency.
Abstract: A case-control design involving only cases may be used when brief exposure causes a transient change in risk of a rare acute-onset disease. The design resembles a retrospective nonrandomized crossover study but differs in having only a sample of the base population-time. The average incidence rate ratio for a hypothesized effect period following the exposure is estimable using the Mantel-Haenszel estimator. The duration of the effect period is assumed to be that which maximizes the rate ratio estimate. Self-matching of cases eliminates the threat of control-selection bias and increases efficiency. Pilot data from a study of myocardial infarction onset illustrate the control of within-individual confounding due to temporal association of exposures.
TL;DR: In this paper, an analysis of the IR data using numerical simulations based on an average single chain model suggests that the alkyl chains in monolayers on silver are all-trans zig-zag and canted by - 12' from the normal to the surface.
Abstract: Long-chain alkanethiols, HS(CH2),CH3, adsorb from solution onto.the surfaces of gold, silver, and copper and form monolayers. Reflection infrared spectroscopy indicates that monolayers on silver and on copper (when carefully prepared) have the chains in well-defined molecular orientations and in crystalline-like phase states, as has been observed on gold. Monolayers on silver are structurally related to those formed by adsorption on gold, but different in details of orientation. The monolayers formed on copper are structurally more complex and show a pronounced sensitivity to the details of the sample preparation. Quantitative analysis of the IR data using numerical simulations based on an average single chain model suggests that the alkyl chains in monolayers on silver are all-trans zig-zag and canted by - 12' from the normal to the surface. The analysis also suggests a twist of the plane containing the carbon backbone of -45' from the plane defined by the tilt and surface normal vectors. For comparison, the monolayers that form on adsorption of alkanethiols on gold surfaces, as judged by their vibrational spectra, are also trans zig-zag extended but, when interpreted in the context of the same single chain model, have a cant angle of -27O and a twist of the plane of the carbon backbone of -53'. The monolayers formed on copper (when they are obtained in high quality) exhibit infrared spectra effectively indistinguishable from those on silver and thus appear to have the same structure. Films on copper are also commonly obtained that are structurally ill-defined and appear to contain significant densities of gauche conformations. These spectroscopically based interpretations are compatible with inferences from wetting and XPS measurements. The structure of the substrate-sulfur interface appears to control molecular orientations of the alkyl groups in these films. An improved structural model, incorporating a two-chain unit cell and allowing for the temperature-dependent population of gauche conformations, is presented and applied to the specific case of the structures formed on gold.
TL;DR: It is found that 14/24 (58%) of invasive squamous cell carcinomas of the skin contain mutations in the p53 tumor suppressor gene, each altering the amino acid sequence, which is believed to identify a carcinogen-related step in a gene involved in the subsequent human cancer.
Abstract: Sunlight is a carcinogen to which everyone is exposed. Its UV component is the major epidemiologic risk factor for squamous cell carcinoma of the skin. Of the multiple steps in tumor progression, those that are sunlight-related would be revealed if they contained mutations specific to UV. In a series of New England and Swedish patients, we find that 14/24 (58%) of invasive squamous cell carcinomas of the skin contain mutations in the p53 tumor suppressor gene, each altering the amino acid sequence. Involvement of UV light in these p53 mutations is indicated by the presence in three of the tumors of a CC----TT double-base change, which is only known to be induced by UV. UV is also implicated by a UV-like occurrence of mutations exclusively at dipyrimidine sites, including a high frequency of C----T substitutions. p53 mutations in internal malignancies do not show these UV-specific mutations. The dipyrimidine specificity also implicates dipyrimidine photoproducts containing cytosine as oncogenic photoproducts. We believe these results identify a carcinogen-related step in a gene involved in the subsequent human cancer.
TL;DR: The State Self-Esteem Scale (SSES) as mentioned in this paper is a modified version of the Janis-Field Feelings of Inadequacy Scale (Janis & Field, 1959).
Abstract: This article examines the measurement of short-lived (i.e., state) changes in self-esteem. A new scale is introduced that is sensitive to manipulations designed to temporarily alter self-esteem, and 5 studies are presented that support the scale's validity. The State Self-Esteem Scale (SSES) consists of 20 items modified from the widely used Janis-Field Feelings of Inadequacy Scale (Janis & Field, 1959). Psychometric analyses revealed that the SSES has 3 correlated factors: performance, social, and appearance self-esteem. Effects of naturally occurring and laboratory failure and of clinical treatment on SSES scores were examined; it was concluded that the SSES is sensitive to these sorts of manipulations. The scale has many potential uses, which include serving as a valid manipulation check index, measuring clinical change in self-esteem, and untangling the confounded relation between mood and self-esteem.
TL;DR: Self-assembled monolayers of omega-functionalized long-chain alkanethiolates on gold films are excellent model systems with which to study the interactions of proteins with organic surfaces and the ability to create interfaces with similar structures and well-defined compositions should make it possible to test hypotheses concerning protein adsorption.
Abstract: Self-assembled monolayers (SAMs) of ω-functionalized long-chain alkanethiolates on gold films are excellent model systems with which to study the interactions of proteins with organic surfaces. Mon...
Posted Content•
TL;DR: In this paper, the generalized autoregressive conditionally heteroskedastic (GARCH) model of returns is modified to allow for volatility feedback effect, which amplifies large negative stock returns and dampens large positive returns, making stock returns negatively skewed and increasing the potential for large crashes.
Abstract: It is sometimes argued that an increase in stock market volatility raises required stock returns, and thus lowers stock prices. This paper modifies the generalized autoregressive conditionally heteroskedastic (GARCH) model of returns to allow for this volatility feedback effect. The resulting model is asymmetric, because volatility feedback amplifies large negative stock returns and dampens large positive returns, making stock returns negatively skewed and increasing the potential for large crashes. The model also implies that volatility feedback is more important when volatility is high. In U.S. monthly and daily data in the period 1926-88, the asymmetric model fits the data better than the standard GARCH model, accounting for almost half the skewness and excess kurtosis of standard monthly GARCH residuals. Estimated volatility discounts on the stock market range from 1% in normal times to 13% after the stock market crash of October 1987 and 25% in the early 1930's. However volatility feedback has little effect on the unconditional variance of stock returns.
TL;DR: This technique was used to generate the first functional magnetic resonance maps of human task activation, by using a visual stimulus paradigm, and localized increases in blood volume were detected in the primary visual cortex during photic stimulation.
Abstract: Knowledge of regional cerebral hemodynamics has widespread application for both physiological research and clinical assessment because of the well-established interrelation between physiological function, energy metabolism, and localized blood supply. A magnetic resonance technique was developed for quantitative imaging of cerebral hemodynamics, allowing for measurement of regional cerebral blood volume during resting and activated cognitive states. This technique was used to generate the first functional magnetic resonance maps of human task activation, by using a visual stimulus paradigm. During photic stimulation, localized increases in blood volume (32 +/- 10 percent, n = 7 subjects) were detected in the primary visual cortex. Center-of-mass coordinates and linear extents of brain activation within the plane of the calcarine fissure are reported.
TL;DR: The literature supports considerable comorbidity of attention deficit hyperactivity disorder with conduct disorder, oppositional defiant disorder, mood disorders, anxiety disorders, learning disabilities, and other disorders, such as mental retardation, Tourette's syndrome, and borderline personality disorder.
Abstract: Objective Attention deficit hyperactivity disorder is a heterogeneous disorder of unknown etiology Little is known about the comorbidity of this disorder with disorders other than conduct Therefore, the authors made a systematic search of the psychiatric and psychological literature for empirical studies dealing with the comorbidity of attention deficit hyperactivity disorder with other disorders Data collection The search terms included hyperactivity, hyperkinesis, attention deficit disorder, and attention deficit hyperactivity disorder, cross-referenced with antisocial disorder (aggression, conduct disorder, antisocial disorder), depression (depression, mania, depressive disorder, bipolar), anxiety (anxiety disorder, anxiety), learning problems (learning, learning disability, academic achievement), substance abuse (alcoholism, drug abuse), mental retardation, and Tourette's disorder Findings The literature supports considerable comorbidity of attention deficit hyperactivity disorder with conduct disorder, oppositional defiant disorder, mood disorders, anxiety disorders, learning disabilities, and other disorders, such as mental retardation, Tourette's syndrome, and borderline personality disorder Conclusions Subgroups of children with attention deficit hyperactivity disorder might be delineated on the basis of the disorder's comorbidity with other disorders These subgroups may have differing risk factors, clinical courses, and pharmacological responses Thus, their proper identification may lead to refinements in preventive and treatment strategies Investigation of these issues should help to clarify the etiology, course, and outcome of attention deficit hyperactivity disorder
TL;DR: In this paper, the authors construct topological invariants of compact oriented 3-manifolds and of framed links in such manifolds, where the terms of the sequence are equale to the values of the Jones polynomial of the link in the corresponding roots of 1.
Abstract: The aim of this paper is to construct new topological invariants of compact oriented 3-manifolds and of framed links in such manifolds. Our invariant of (a link in) a closed oriented 3-manifold is a sequence of complex numbers parametrized by complex roots of 1. For a framed link in S 3 the terms of the sequence are equale to the values of the (suitably parametrized) Jones polynomial of the link in the corresponding roots of 1. In the case of manifolds with boundary our invariant is a (sequence of) finite dimensional complex linear operators. This produces from each root of unity q a 3-dimensional topological quantum field theory
TL;DR: The extent of bone-implant interface is positively correlated with an increasing roughness of the implant surface, and hydroxylapatite (HA)-coated implants with 60-70% showed signs of resorption.
Abstract: The purpose of the present study was to evaluate the influence of different surface characteristics on bone integration of titanium implants. Hollow-cylinder implants with six different surfaces were placed in the metaphyses of the tibia and femur in six miniature pigs. After 3 and 6 weeks, the implants with surrounding bone were removed and analyzed in undecalcified transverse sections. The histologic examination revealed direct bone-implant contact for all implants. However, the morphometric analyses demonstrated significant differences in the percentage of bone-implant contact, when measured in cancellous bone. Electropolished as well as the sandblasted and acid pickled (medium grit; HF/HNO3) implant surfaces had the lowest percentage of bone contact with mean values ranging between 20 and 25%. Sandblasted implants with a large grit and titanium plasma-sprayed implants demonstrated 30-40% mean bone contact. The highest extent of bone-implant interface was observed in sandblasted and acid attacked surfaces (large grit; HCl/H2SO4) with mean values of 50-60%, and hydroxylapatite (HA)-coated implants with 60-70%. However, the HA coating consistently revealed signs of resorption. It can be concluded that the extent of bone-implant interface is positively correlated with an increasing roughness of the implant surface.
TL;DR: This paper found that countries with a higher proportion of engineering college majors grow faster than countries with lower proportion of law concentrators, whereas countries with high proportion of business concentrators grow more slowly.
Abstract: A country's most talented people typically organize production by others, so they can spread their ability advantage over a larger scale. When they start firms, they innovate and foster growth, but when they become rent seekers, they only redistribute wealth and reduce growth. Occupational choice depends on returns to ability and to scale in each sector, on market size, and on compensation contracts. In most countries, rent seeking rewards talent more than entrepreneurship does, leading to stagnation. Our evidence shows that countries with a higher proportion of engineering college majors grow faster; whereas countries with a higher proportion of law concentrators grow more slowly.